Using Gitea-compatible upload-artifact action

Also improved error reporting for common failure cases.

.gitattributes

@@ -0,0 +1,4 @@
+*.psk filter=lfs diff=lfs merge=lfs -text
+*.psa filter=lfs diff=lfs merge=lfs -text
+*.pskx filter=lfs diff=lfs merge=lfs -text
+*.blend filter=lfs diff=lfs merge=lfs -text

.github/FUNDING.yml

@@ -0,0 +1 @@
+ko_fi: cmbasnett

.github/ISSUE_TEMPLATE/bug_report.md

@@ -0,0 +1,34 @@
+---
+name: Bug report
+about: Create a report to help us improve
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Versions**
+Blender: (example: 3.6.2)
+io_scene_psk_psa: (example: 5.0.0)
+
+**Describe the bug**
+A clear and concise description of what the bug is.
+
+**To Reproduce**
+Steps to reproduce the behavior:
+1. Go to '...'
+2. Click on '....'
+3. Scroll down to '....'
+4. See error
+
+**Expected behavior**
+A clear and concise description of what you expected to happen.
+
+**Screenshots**
+If applicable, add screenshots to help explain your problem.
+
+**Files**
+Please post attachments of the PSK and/or PSA files that you are using to encounter the bug, if any.
+
+**Additional context**
+Add any other context about the problem here.

.github/ISSUE_TEMPLATE/feature_request.md

@@ -0,0 +1,20 @@
+---
+name: Feature request
+about: Suggest an idea for this project
+title: ''
+labels: ''
+assignees: ''
+
+---
+
+**Is your feature request related to a problem? Please describe.**
+A clear and concise description of what the problem is. Ex. I'm always frustrated when [...]
+
+**Describe the solution you'd like**
+A clear and concise description of what you want to happen.
+
+**Describe alternatives you've considered**
+A clear and concise description of any alternative solutions or features you've considered.
+
+**Additional context**
+Add any other context or screenshots about the feature request here.

.github/workflows/main.yml

@@ -0,0 +1,80 @@
+name: tests
+
+on:
+  workflow_dispatch:
+  push:
+    branches: [ "main" ]
+  pull_request:
+    branches: [ "main" ]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    strategy:
+      matrix:
+        blender-version: [ 5.0 ]
+    env:
+      ADDON_NAME: io_scene_psk_psa
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          persist-credentials: true
+      - name: Checkout LFS objects
+        run: |
+          git lfs install --local
+          AUTH=$(git config --local http.${{ github.server_url }}/.extraheader)
+          git config --local --unset http.${{ github.server_url }}/.extraheader
+          git config --local http.${{ github.server_url }}/${{ github.repository }}.git/info/lfs/objects/batch.extraheader "$AUTH"
+          git lfs pull
+      - uses: SebRollen/toml-action@v1.2.0
+        id: read_manifest
+        with:
+          file: '${{ env.ADDON_NAME }}/blender_manifest.toml'
+          field: 'version'
+      - name: Install Blender Dependencies
+        run: |
+          sudo apt-get update -y
+          sudo apt-get install libxxf86vm-dev -y
+          sudo apt-get install libxfixes3 -y
+          sudo apt-get install libxi-dev -y
+          sudo apt-get install libxkbcommon-x11-0 -y
+          sudo apt-get install libgl1 -y
+          sudo apt-get install libglx-mesa0 -y
+          sudo apt-get install python3 -y
+      - name: Install Requirements
+        run: |
+          sudo apt-get install python3-virtualenv -y
+          python3 -m virtualenv venv
+          source venv/bin/activate
+          pip install pytest-blender
+          pip install blender-downloader
+      - name: Install Blender
+        run: |
+          source venv/bin/activate
+          blender_executable="$(blender-downloader ${{ matrix.blender-version }} --extract --print-blender-executable)"
+          echo "BLENDER_EXECUTABLE=${blender_executable}" >> $GITHUB_ENV
+          blender_python="$(pytest-blender --blender-executable "$blender_executable")"
+          echo "BLENDER_PYTHON=${blender_python}" >> $GITHUB_ENV
+          # Write the BLENDER_PYTHON path to the console for debugging
+          # Deactivate the virtualenv to avoid conflicts with the system python
+          deactivate
+          $blender_python -m ensurepip
+          $blender_python -m pip install -r tests/requirements.txt
+      - name: Build extension
+        run: |
+          pushd ./${{ env.ADDON_NAME }}
+          # Run blender using the environment variable set by the action
+          ${{ env.BLENDER_EXECUTABLE }} --command extension build
+          mkdir artifact
+          unzip -q ${{ env.ADDON_NAME }}-${{ steps.read_manifest.outputs.value }}.zip -d ./artifact
+          popd
+      - name: Run tests
+        run: |
+          source venv/bin/activate
+          pytest -svv tests --blender-addons-dirs .
+      - name: Archive addon
+        uses: https://github.com/christopherHX/gitea-upload-artifact@v4
+        with:
+          name: ${{ env.ADDON_NAME }}-${{ github.ref_name }}-${{ github.sha }}
+          path: |
+            ./${{ env.ADDON_NAME }}/artifact/*

.gitignore

@@ -105,3 +105,4 @@ venv.bak/
 
 # PyCharm
 .idea
+*.blend1

.vscode/tasks.json

@@ -0,0 +1,17 @@
+{
+    // See https://go.microsoft.com/fwlink/?LinkId=733558
+    // for the documentation about the tasks.json format
+    "version": "2.0.0",
+    "tasks": [
+        {
+            "label": "io_scene_psk_psa: test",
+            "type": "shell",
+            "command": "docker run -it --volume ${PWD}:/io_scene_psk_psa --volume ${PWD}/io_scene_psk_psa:/addons/io_scene_psk_psa --volume ${PWD}/tests:/tests  $(docker build -q .)",
+            "problemMatcher": [],
+            "group": {
+                "kind": "build",
+                "isDefault": true
+            }
+        }
+    ]
+}

COPYING

@@ -0,0 +1,674 @@
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+  Nothing in this License shall be construed as excluding or limiting
+any implied license or other defenses to infringement that may
+otherwise be available to you under applicable patent law.
+
+  12. No Surrender of Others' Freedom.
+
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+
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+
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+
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+to attach them to the start of each source file to most effectively
+state the exclusion of warranty; and each file should have at least
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+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+Also add information on how to contact you by electronic and paper mail.
+
+  If the program does terminal interaction, make it output a short
+notice like this when it starts in an interactive mode:
+
+    <program>  Copyright (C) <year>  <name of author>
+    This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
+    This is free software, and you are welcome to redistribute it
+    under certain conditions; type `show c' for details.
+
+The hypothetical commands `show w' and `show c' should show the appropriate
+parts of the General Public License.  Of course, your program's commands
+might be different; for a GUI interface, you would use an "about box".
+
+  You should also get your employer (if you work as a programmer) or school,
+if any, to sign a "copyright disclaimer" for the program, if necessary.
+For more information on this, and how to apply and follow the GNU GPL, see
+<https://www.gnu.org/licenses/>.
+
+  The GNU General Public License does not permit incorporating your program
+into proprietary programs.  If your program is a subroutine library, you
+may consider it more useful to permit linking proprietary applications with
+the library.  If this is what you want to do, use the GNU Lesser General
+Public License instead of this License.  But first, please read
+<https://www.gnu.org/licenses/why-not-lgpl.html>.

Dockerfile

@@ -0,0 +1,35 @@
+FROM ubuntu:22.04
+
+RUN apt-get update -y && \
+    apt-get install -y libxxf86vm-dev libxfixes3 libxi-dev libxkbcommon-x11-0 libgl1 libglx-mesa0 python3 python3-pip \
+    libxrender1 libsm6
+
+RUN pip install --upgrade pip
+RUN pip install pytest-blender
+RUN pip install blender-downloader
+
+ARG BLENDER_VERSION=5.0
+
+# Set BLENDER_EXECUTABLE and BLENDER_PYTHON as environment variables
+RUN BLENDER_EXECUTABLE=$(blender-downloader $BLENDER_VERSION --extract --remove-compressed --print-blender-executable) && \
+    BLENDER_PYTHON=$(pytest-blender --blender-executable "${BLENDER_EXECUTABLE}") && \
+    echo "export BLENDER_EXECUTABLE=${BLENDER_EXECUTABLE}" >> /etc/environment && \
+    echo "export BLENDER_PYTHON=${BLENDER_PYTHON}" >> /etc/environment && \
+    echo $BLENDER_EXECUTABLE > /blender_executable_path
+
+RUN pip install pytest-cov
+
+# Source the environment variables and install Python dependencies
+# TODO: would be nice to have these installed in the bash script below.
+RUN . /etc/environment && \
+    $BLENDER_PYTHON -m ensurepip && \
+    $BLENDER_PYTHON -m pip install pytest pytest-cov psk-psa-py==0.0.4
+
+# Persist BLENDER_EXECUTABLE as an environment variable
+RUN echo $(cat /blender_executable_path) > /tmp/blender_executable_path_env && \
+    export BLENDER_EXECUTABLE=$(cat /tmp/blender_executable_path_env)
+ENV BLENDER_EXECUTABLE /tmp/blender_executable_path_env
+
+ENTRYPOINT [ "/bin/bash", "-c" ]
+WORKDIR /io_scene_psk_psa
+CMD ["source tests/test.sh"]

LICENSE

@@ -1,21 +0,0 @@
-MIT License
-
-Copyright (c) 2019 Darklight Games
-
-Permission is hereby granted, free of charge, to any person obtaining a copy
-of this software and associated documentation files (the "Software"), to deal
-in the Software without restriction, including without limitation the rights
-to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
-copies of the Software, and to permit persons to whom the Software is
-furnished to do so, subject to the following conditions:
-
-The above copyright notice and this permission notice shall be included in all
-copies or substantial portions of the Software.
-
-THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
-IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
-FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
-AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
-LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
-OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
-SOFTWARE.

README.md

@@ -1,3 +1,96 @@
-# io_export_psk_psa
+[![Blender](https://img.shields.io/badge/Blender%20Extension-Download-blue?logo=blender&logoColor=white)](https://extensions.blender.org/add-ons/io-scene-psk-psa/ "Download Blender")
+[![tests](https://github.com/DarklightGames/io_scene_psk_psa/actions/workflows/main.yml/badge.svg)](https://github.com/DarklightGames/io_scene_psk_psa/actions/workflows/main.yml)
 
-If you are looking for a PSK/PSA importer, use [this one](https://github.com/Befzz/blender3d_import_psk_psa)!
+[![ko-fi](https://ko-fi.com/img/githubbutton_sm.svg)](https://ko-fi.com/L4L3853VR)
+
+This Blender addon allows you to import and export meshes and animations to and from the [PSK and PSA file formats](https://wiki.beyondunreal.com/PSK_%26_PSA_file_formats) used in many versions of the Unreal Engine.
+
+This software is licensed under the [GPLv3](https://www.gnu.org/licenses/gpl-3.0.html) license.
+
+# Installation
+For Blender 4.2 and higher, download the latest version from the [Blender Extensions](https://extensions.blender.org/add-ons/io-scene-psk-psa/) platform.
+
+For Blender 4.1 and lower, see [Legacy Compatibility](#legacy-compatibility).
+
+# Features
+* [Bone collections](https://docs.blender.org/manual/en/latest/animation/armatures/bones/bone_collections.html#bone-collections) can be excluded from PSK/PSA export (useful for excluding non-contributing bones such as IK controllers).
+* [Collection Exporters](https://docs.blender.org/manual/en/latest/scene_layout/collections/collections.html#exporters) for reliable, repeatable export workflow.
+* Non-standard model data (.pskx) is supported for import only (vertex normals, extra UV channels, vertex colors, shape keys).
+* Manual re-ordering of material slots on export.
+* Non-standard animation data is supported for import only (scale keys).
+* Fine-grained PSA sequence importing for efficient workflow when working with large PSA files.
+* PSA sequence metadata (e.g., frame rate) is preserved on import, allowing this data to be reused on export.
+* PSA sequences can be exported directly from actions or delineated using a scene's [timeline markers](https://docs.blender.org/manual/en/latest/animation/markers.html), pose markers, or NLA track strips, allowing direct use of the [NLA](https://docs.blender.org/manual/en/latest/editors/nla/index.html) when creating sequences.
+* Compress exported sequences via resampling ratios or frame quotas.
+
+# Usage
+
+## Import
+
+### Importing a PSK/PSKX
+1. Navigate to `File` > `Import` > `Unreal PSK (.psk/.pskx)`.
+2. Select the PSK file you want to import and click `Import`.
+
+### Importing a PSA
+1. Select an armature that you want import animations for.
+2. Navigate to `File` > `Import` > `Unreal PSA (.psa)`.
+3. Select the PSA file you want to import.
+4. Select the sequences that you want to import and click `Import`.
+
+## Export
+It is highly recommended to use the provided [Collection Exporters](https://docs.blender.org/manual/en/latest/scene_layout/collections/collections.html#exporters) workflow, since it allows for highly reliable, repeatable exports of both PSK and PSA files. However, the traditional export workflow is available as well.
+
+### Exporting a PSK
+1. Select the mesh objects you wish to export.
+2. Navigate to `File` > `Export` > `Unreal PSK (.psk)`.
+3. Enter the file name and click `Export`.
+
+### Exporting a PSA
+1. Select the armature objects you wish to export.
+2. Navigate to `File` > `Export` > `Unreal PSA (.psa)`.
+3. Enter the file name and click `Export`.
+
+> Note that in order to see the imported actions applied to your armature, you must use the [Dope Sheet](https://docs.blender.org/manual/en/latest/editors/dope_sheet/introduction.html) or [Nonlinear Animation](https://docs.blender.org/manual/en/latest/editors/nla/introduction.html) editors.
+
+# FAQ
+
+## Why can't I see the animations imported from my PSA?
+Simply importing an animation into the scene will not automatically apply the action to the armature. This is in part because a PSA can have multiple sequences imported from it, and also that it's generally bad form for importers to modify the scene in ways that the user may not expect.
+
+The PSA importer creates [Actions](https://docs.blender.org/manual/en/latest/animation/actions.html) for each of the selected sequences in the PSA. These actions can be applied to your armature via the [Action Editor](https://docs.blender.org/manual/en/latest/editors/dope_sheet/action.html) or [NLA Editor](https://docs.blender.org/manual/en/latest/editors/nla/index.html).
+
+## Why are imported PSKs too big/too small?
+The PSK format, unlike other more modern formats, has no explicit or implicit unit system. Each game has its own convention as to what the base distance unit will represent. As such, this addon makes no assumptions as to the unit scale of the imported PSKs. If you think that your models are being imported into Blender either too big or too small, there are a couple ways to remedy this.
+
+The method I prefer is to simply change the Blender [scene properties](https://docs.blender.org/manual/en/5.0/scene_layout/scene/properties.html#units) to match the unit system and scale for the game you're using. This is non-destructive and ensures that the unit scaling of any PSK or PSA exports from Blender will match the source file from which it was derived.
+
+The second option is to simply change the `Scale` value on the PSK import dialog. This will scale the armature by the factor provided. Note that this is more destructive, but may be preferable if you don't intend on exporting PSKs or PSAs to a game engine.
+
+## How do I control shading for PSK exports?
+The PSK format does not support vertex normals and instead uses [smoothing groups](https://en.wikipedia.org/wiki/Smoothing_group) to control shading. Note that a mesh's Custom Split Normals Data will be ignored when exporting to PSK. Therefore, the best way to control shading is to use sharp edges and the Edge Split modifier.
+
+## Why are the mesh normals not accurate when importing a PSK extracted from [UE Viewer](https://www.gildor.org/en/projects/umodel)?
+If preserving the mesh normals of models is important for your workflow, it is *not recommended* to export PSK files from UE Viewer. This is because UE Viewer makes no attempt to reconstruct the original [smoothing groups](https://en.wikipedia.org/wiki/Smoothing_group). As a result, the normals of imported PSK files will be incorrect when imported into Blender and will need to be manually fixed.
+
+There is a [pull request](https://github.com/gildor2/UEViewer/pull/277) to add support for exporting explicit normals from UE Viewer, although UEViewer's maintainer has seemingly abandoned the project.
+
+# Legacy Compatibility
+Below is a table of the latest addon versions that are compatible with older versions of Blender. These versions are no longer maintained and may contain bugs that have been fixed in newer versions. It is recommended to use the latest version of the addon for the best experience.
+
+| Blender Version| Addon Version |
+|-|-|
+| [4.1](https://www.blender.org/download/releases/4-1/)        | [7.0.0](https://github.com/DarklightGames/io_scene_psk_psa/releases/tag/7.0.0) |
+| [4.0](https://www.blender.org/download/releases/4-0/)        | [6.2.1](https://github.com/DarklightGames/io_scene_psk_psa/releases/tag/6.2.1) |
+| [3.4 - 3.6](https://www.blender.org/download/lts/3-6/)       | [5.0.6](https://github.com/DarklightGames/io_scene_psk_psa/releases/tag/5.0.6) |
+| [2.93 - 3.3](https://www.blender.org/download/releases/3-3/) | [4.3.0](https://github.com/DarklightGames/io_scene_psk_psa/releases/tag/4.3.0) |
+
+# Testing
+To execute the automated tests, run:
+
+```
+./test.sh
+````
+
+This will create a [Docker](https://www.docker.com/) container with and run the tests inside it. The tests are executed using [pytest](https://docs.pytest.org/en/stable/) and the results will be displayed in the terminal.
+
+For now, the tests are not exhaustive and primarily focus on sanity checking the most common use cases (PSK & PSA import). New tests will likely be made to cover new features and prevent further regressions of reported issues.

io_export_psk_psa/__init__.py

@@ -1,73 +0,0 @@
-bl_info = {
-    "name": "PSK/PSA Exporter",
-    "author": "Colin Basnett",
-    "version": ( 1, 0, 0 ),
-    "blender": ( 2, 80, 0 ),
-    "location": "File > Export > PSK Export (.psk)",
-    "description": "PSK/PSA Export (.psk)",
-    "warning": "",
-    "wiki_url": "https://github.com/DarklightGames/io_export_psk_psa",
-    "tracker_url": "https://github.com/DarklightGames/io_export_psk_psa/issues",
-    "category": "Import-Export"
-}
-
-if 'bpy' in locals():
-    import importlib
-    importlib.reload(psk_data)
-    importlib.reload(psk_builder)
-    importlib.reload(psk_exporter)
-    importlib.reload(psk_operator)
-    importlib.reload(psa_data)
-    importlib.reload(psa_builder)
-    importlib.reload(psa_exporter)
-    importlib.reload(psa_operator)
-else:
-    # if i remove this line, it can be enabled just fine
-    from .psk import data as psk_data
-    from .psk import builder as psk_builder
-    from .psk import exporter as psk_exporter
-    from .psk import operator as psk_operator
-    from .psa import data as psa_data
-    from .psa import builder as psa_builder
-    from .psa import exporter as psa_exporter
-    from .psa import operator as psa_operator
-
-import bpy
-from bpy.props import IntProperty, CollectionProperty
-
-classes = [
-    psk_operator.PskExportOperator,
-    psa_operator.PsaExportOperator,
-    psa_operator.PSA_UL_ActionList,
-    psa_operator.ActionListItem
-]
-
-
-def psk_menu_func(self, context):
-    self.layout.operator(psk_operator.PskExportOperator.bl_idname, text ='Unreal PSK (.psk)')
-
-
-def psa_menu_func(self, context):
-    self.layout.operator(psa_operator.PsaExportOperator.bl_idname, text='Unreal PSA (.psa)')
-
-
-def register():
-    for cls in classes:
-        bpy.utils.register_class(cls)
-    bpy.types.TOPBAR_MT_file_export.append(psk_menu_func)
-    bpy.types.TOPBAR_MT_file_export.append(psa_menu_func)
-    bpy.types.Scene.psa_action_list = CollectionProperty(type=psa_operator.ActionListItem)
-    bpy.types.Scene.psa_action_list_index = IntProperty(name='index for list??', default=0)
-
-
-def unregister():
-    del bpy.types.Scene.psa_action_list_index
-    del bpy.types.Scene.psa_action_list
-    bpy.types.TOPBAR_MT_file_export.remove(psa_menu_func)
-    bpy.types.TOPBAR_MT_file_export.remove(psk_menu_func)
-    for cls in reversed(classes):
-        bpy.utils.unregister_class(cls)
-
-
-if __name__ == '__main__':
-    register()

io_export_psk_psa/data.py

@@ -1,31 +0,0 @@
-from ctypes import *
-
-
-class Vector3(Structure):
-    _fields_ = [
-        ('x', c_float),
-        ('y', c_float),
-        ('z', c_float),
-    ]
-
-
-class Quaternion(Structure):
-    _fields_ = [
-        ('x', c_float),
-        ('y', c_float),
-        ('z', c_float),
-        ('w', c_float),
-    ]
-
-
-class Section(Structure):
-    _fields_ = [
-        ('name', c_char * 20),
-        ('type_flags', c_int32),
-        ('data_size', c_int32),
-        ('data_count', c_int32)
-    ]
-
-    def __init__(self, *args, **kw):
-        super().__init__(*args, **kw)
-        self.type_flags = 1999801

io_export_psk_psa/psa/builder.py

@@ -1,130 +0,0 @@
-from .data import *
-
-
-class PsaBuilderOptions(object):
-    def __init__(self):
-        self.actions = []
-
-
-# https://git.cth451.me/cth451/blender-addons/blob/master/io_export_unreal_psk_psa.py
-class PsaBuilder(object):
-    def __init__(self):
-        # TODO: add options in here (selected anims, eg.)
-        pass
-
-    def build(self, context, options) -> Psa:
-        object = context.view_layer.objects.active
-
-        if object.type != 'ARMATURE':
-            raise RuntimeError('Selected object must be an Armature')
-
-        armature = object
-
-        if armature.animation_data is None:
-            raise RuntimeError('No animation data for armature')
-
-        psa = Psa()
-
-        bones = list(armature.data.bones)
-
-        # The order of the armature bones and the pose bones is not guaranteed to be the same.
-        # As as a result, we need to reconstruct the list of pose bones in the same order as the
-        # armature bones.
-        bone_names = [x.name for x in bones]
-        pose_bones = [(bone_names.index(bone.name), bone) for bone in armature.pose.bones]
-        pose_bones.sort(key=lambda x: x[0])
-        pose_bones = [x[1] for x in pose_bones]
-
-        for bone in bones:
-            psa_bone = Psa.Bone()
-            psa_bone.name = bytes(bone.name, encoding='utf-8')
-            psa_bone.children_count = len(bone.children)
-
-            try:
-                psa_bone.parent_index = bones.index(bone.parent)
-            except ValueError:
-                psa_bone.parent_index = -1
-
-            if bone.parent is not None:
-                rotation = bone.matrix.to_quaternion()
-                rotation.x = -rotation.x
-                rotation.y = -rotation.y
-                rotation.z = -rotation.z
-                quat_parent = bone.parent.matrix.to_quaternion().inverted()
-                parent_head = quat_parent @ bone.parent.head
-                parent_tail = quat_parent @ bone.parent.tail
-                location = (parent_tail - parent_head) + bone.head
-            else:
-                location = armature.matrix_local @ bone.head
-                rot_matrix = bone.matrix @ armature.matrix_local.to_3x3()
-                rotation = rot_matrix.to_quaternion()
-
-            psa_bone.location.x = location.x
-            psa_bone.location.y = location.y
-            psa_bone.location.z = location.z
-
-            psa_bone.rotation.x = rotation.x
-            psa_bone.rotation.y = rotation.y
-            psa_bone.rotation.z = rotation.z
-            psa_bone.rotation.w = rotation.w
-
-            psa.bones.append(psa_bone)
-
-        frame_start_index = 0
-
-        for action in options.actions:
-            if len(action.fcurves) == 0:
-                continue
-
-            armature.animation_data.action = action
-            context.view_layer.update()
-
-            frame_min, frame_max = [int(x) for x in action.frame_range]
-
-            sequence = Psa.Sequence()
-            sequence.name = bytes(action.name, encoding='utf-8')
-            sequence.frame_count = frame_max - frame_min + 1
-            sequence.frame_start_index = frame_start_index
-            sequence.fps = 30  # TODO: fill in later with r
-
-            frame_count = frame_max - frame_min + 1
-
-            for frame in range(frame_count):
-                context.scene.frame_set(frame)
-
-                for bone in pose_bones:
-                    # TODO: is the cast-to-matrix necessary? (guessing no)
-                    key = Psa.Key()
-                    pose_bone_matrix = bone.matrix
-
-                    if bone.parent is not None:
-                        pose_bone_parent_matrix = bone.parent.matrix
-                        pose_bone_matrix = pose_bone_parent_matrix.inverted() @ pose_bone_matrix
-
-                    location = pose_bone_matrix.to_translation()
-                    rotation = pose_bone_matrix.to_quaternion().normalized()
-
-                    if bone.parent is not None:
-                        rotation.x = -rotation.x
-                        rotation.y = -rotation.y
-                        rotation.z = -rotation.z
-
-                    key.location.x = location.x
-                    key.location.y = location.y
-                    key.location.z = location.z
-                    key.rotation.x = rotation.x
-                    key.rotation.y = rotation.y
-                    key.rotation.z = rotation.z
-                    key.rotation.w = rotation.w
-                    key.time = 1.0 / sequence.fps
-
-                    psa.keys.append(key)
-
-                frame_start_index += 1
-
-                sequence.bone_count = len(pose_bones)
-                sequence.track_time = frame_count
-
-            psa.sequences.append(sequence)
-
-        return psa

io_export_psk_psa/psa/data.py

@@ -1,44 +0,0 @@
-from typing import List
-from ..data import *
-
-
-class Psa(object):
-
-    class Bone(Structure):
-        _fields_ = [
-            ('name', c_char * 64),
-            ('flags', c_int32),
-            ('children_count', c_int32),
-            ('parent_index', c_int32),
-            ('rotation', Quaternion),
-            ('location', Vector3),
-            ('padding', c_char * 16)
-        ]
-
-    class Sequence(Structure):
-        _fields_ = [
-            ('name', c_char * 64),
-            ('group', c_char * 64),
-            ('bone_count', c_int32),
-            ('root_include', c_int32),
-            ('compression_style', c_int32),
-            ('key_quotum', c_int32),  # what the fuck is a quotum
-            ('key_reduction', c_float),
-            ('track_time', c_float),
-            ('fps', c_float),
-            ('start_bone', c_int32),
-            ('frame_start_index', c_int32),
-            ('frame_count', c_int32)
-        ]
-
-    class Key(Structure):
-        _fields_ = [
-            ('location', Vector3),
-            ('rotation', Quaternion),
-            ('time', c_float)
-        ]
-
-    def __init__(self):
-        self.bones: List[Psa.Bone] = []
-        self.sequences: List[Psa.Sequence] = []
-        self.keys: List[Psa.Key] = []

io_export_psk_psa/psa/exporter.py

@@ -1,27 +0,0 @@
-from typing import Type
-from .data import *
-
-
-class PsaExporter(object):
-    def __init__(self, psa: Psa):
-        self.psa: Psa = psa
-
-    # This method is shared by both PSA/K file formats, move this?
-    @staticmethod
-    def write_section(fp, name: bytes, data_type: Type[Structure] = None, data: list = None):
-        section = Section()
-        section.name = name
-        if data_type is not None and data is not None:
-            section.data_size = sizeof(data_type)
-            section.data_count = len(data)
-        fp.write(section)
-        if data is not None:
-            for datum in data:
-                fp.write(datum)
-
-    def export(self, path: str):
-        with open(path, 'wb') as fp:
-            self.write_section(fp, b'ANIMHEAD')
-            self.write_section(fp, b'BONENAMES', Psa.Bone, self.psa.bones)
-            self.write_section(fp, b'ANIMINFO', Psa.Sequence, self.psa.sequences)
-            self.write_section(fp, b'ANIMKEYS', Psa.Key, self.psa.keys)

io_export_psk_psa/psa/operator.py

@@ -1,105 +0,0 @@
-from bpy.types import Operator, Action, UIList, PropertyGroup
-from bpy_extras.io_utils import ExportHelper
-from bpy.props import StringProperty, BoolProperty, CollectionProperty, PointerProperty
-from .builder import PsaBuilder, PsaBuilderOptions
-from .exporter import PsaExporter
-import bpy
-import re
-
-
-class ActionListItem(PropertyGroup):
-    action: PointerProperty(type=Action)
-    is_selected: BoolProperty(default=False)
-
-    @property
-    def name(self):
-        return self.action.name
-
-
-class PSA_UL_ActionList(UIList):
-    def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index):
-        layout.alignment = 'LEFT'
-        layout.prop(item, 'is_selected', icon_only=True)
-        layout.label(text=item.action.name)
-
-    def filter_items(self, context, data, property):
-        # TODO: returns two lists, apparently
-        actions = getattr(data, property)
-        flt_flags = []
-        flt_neworder = []
-        if self.filter_name:
-            flt_flags = bpy.types.UI_UL_list.filter_items_by_name(self.filter_name, self.bitflag_filter_item, actions, 'name', reverse=self.use_filter_invert)
-        return flt_flags, flt_neworder
-
-
-class PsaExportOperator(Operator, ExportHelper):
-    bl_idname = 'export.psa'
-    bl_label = 'Export'
-    __doc__ = 'PSA Exporter (.psa)'
-    filename_ext = '.psa'
-    filter_glob : StringProperty(default='*.psa', options={'HIDDEN'})
-    filepath : StringProperty(
-        name='File Path',
-        description='File path used for exporting the PSA file',
-        maxlen=1024,
-        default='')
-
-    def __init__(self):
-        self.armature = None
-
-    def draw(self, context):
-        layout = self.layout
-        scene = context.scene
-        box = layout.box()
-        box.label(text='Actions', icon='ACTION')
-        row = box.row()
-        row.template_list('PSA_UL_ActionList', 'asd', scene, 'psa_action_list', scene, 'psa_action_list_index', rows=len(context.scene.psa_action_list))
-
-    def is_action_for_armature(self, action):
-        if len(action.fcurves) == 0:
-            return False
-        bone_names = set([x.name for x in self.armature.data.bones])
-        for fcurve in action.fcurves:
-            match = re.match(r'pose\.bones\["(.+)"\].\w+', fcurve.data_path)
-            if not match:
-                continue
-            bone_name = match.group(1)
-            if bone_name in bone_names:
-                return True
-        return False
-
-    def invoke(self, context, event):
-        if context.view_layer.objects.active.type != 'ARMATURE':
-            self.report({'ERROR_INVALID_CONTEXT'}, 'The selected object must be an armature.')
-            return {'CANCELLED'}
-
-        self.armature = context.view_layer.objects.active
-
-        context.scene.psa_action_list.clear()
-        for action in bpy.data.actions:
-            item = context.scene.psa_action_list.add()
-            item.action = action
-            if self.is_action_for_armature(action):
-                item.is_selected = True
-
-        if len(context.scene.psa_action_list) == 0:
-            self.report({'ERROR_INVALID_CONTEXT'}, 'There are no actions to export.')
-            return {'CANCELLED'}
-
-        context.window_manager.fileselect_add(self)
-        return {'RUNNING_MODAL'}
-
-    def execute(self, context):
-        actions = [x.action for x in context.scene.psa_action_list if x.is_selected]
-
-        if len(actions) == 0:
-            self.report({'ERROR_INVALID_CONTEXT'}, 'No actions were selected for export.')
-            return {'CANCELLED'}
-
-        options = PsaBuilderOptions()
-        options.actions = actions
-        builder = PsaBuilder()
-        psk = builder.build(context, options)
-        exporter = PsaExporter(psk)
-        exporter.export(self.filepath)
-        return {'FINISHED'}

io_export_psk_psa/psk/builder.py

@@ -1,186 +0,0 @@
-import bpy
-import bmesh
-from collections import OrderedDict
-from .data import *
-
-# https://github.com/bwrsandman/blender-addons/blob/master/io_export_unreal_psk_psa.py
-
-class PskInputObjects(object):
-    def __init__(self):
-        self.mesh_objects = []
-        self.armature_object = None
-
-class PskBuilder(object):
-    def __init__(self):
-        pass
-
-    @staticmethod
-    def get_input_objects(context) -> PskInputObjects:
-        input_objects = PskInputObjects()
-        for obj in context.view_layer.objects.selected:
-            if obj.type != 'MESH':
-                raise RuntimeError(f'Selected object "{obj.name}" is not a mesh')
-
-        input_objects.mesh_objects = context.view_layer.objects.selected
-
-        if len(input_objects.mesh_objects) == 0:
-            raise RuntimeError('At least one mesh must be selected')
-
-        for obj in input_objects.mesh_objects:
-            if len(obj.data.materials) == 0:
-                raise RuntimeError(f'Mesh "{obj.name}" must have at least one material')
-
-        # ensure that there is exactly one armature modifier object shared between all selected meshes
-        armature_modifier_objects = set()
-
-        for obj in input_objects.mesh_objects:
-            modifiers = [x for x in obj.modifiers if x.type == 'ARMATURE']
-            if len(modifiers) != 1:
-                raise RuntimeError(f'Mesh "{obj.name}" must have one armature modifier')
-            armature_modifier_objects.add(modifiers[0].object)
-
-        if len(armature_modifier_objects) > 1:
-            raise RuntimeError('All selected meshes must have the same armature modifier')
-
-        input_objects.armature_object = list(armature_modifier_objects)[0]
-
-        if input_objects.armature_object is None:
-            raise RuntimeError('Armature modifier has no linked object')
-
-        return input_objects
-
-    def build(self, context) -> Psk:
-        input_objects = PskBuilder.get_input_objects(context)
-        wedge_count = sum([len(m.data.loops) for m in input_objects.mesh_objects])
-        if wedge_count <= 65536:
-            wedge_type = Psk.Wedge16
-        else:
-            wedge_type = Psk.Wedge32
-
-        psk = Psk()
-
-        materials = OrderedDict()
-
-        bones = list(input_objects.armature_object.data.bones)
-        for bone in bones:
-            psk_bone = Psk.Bone()
-            psk_bone.name = bytes(bone.name, encoding='utf-8')
-            psk_bone.flags = 0
-            psk_bone.children_count = len(bone.children)
-
-            try:
-                psk_bone.parent_index = bones.index(bone.parent)
-            except ValueError:
-                psk_bone.parent_index = 0
-
-            if bone.parent is not None:
-                rotation = bone.matrix.to_quaternion()
-                rotation.x = -rotation.x
-                rotation.y = -rotation.y
-                rotation.z = -rotation.z
-                quat_parent = bone.parent.matrix.to_quaternion().inverted()
-                parent_head = quat_parent @ bone.parent.head
-                parent_tail = quat_parent @ bone.parent.tail
-                location = (parent_tail - parent_head) + bone.head
-            else:
-                location = input_objects.armature_object.matrix_local @ bone.head
-                rot_matrix = bone.matrix @ input_objects.armature_object.matrix_local.to_3x3()
-                rotation = rot_matrix.to_quaternion()
-
-            psk_bone.location.x = location.x
-            psk_bone.location.y = location.y
-            psk_bone.location.z = location.z
-
-            psk_bone.rotation.x = rotation.x
-            psk_bone.rotation.y = rotation.y
-            psk_bone.rotation.z = rotation.z
-            psk_bone.rotation.w = rotation.w
-
-            psk.bones.append(psk_bone)
-
-        vertex_offset = 0
-        wedge_offset = 0
-        weight_offset = 0
-
-        # TODO: if there is an edge-split modifier, we need to apply it (maybe?)
-        for object in input_objects.mesh_objects:
-            # VERTICES
-            for vertex in object.data.vertices:
-                point = Vector3()
-                v = object.matrix_world @ vertex.co
-                point.x = v.x
-                point.y = v.y
-                point.z = v.z
-                psk.points.append(point)
-
-            # WEDGES
-            uv_layer = object.data.uv_layers.active.data
-            # needs to be additive!!!
-            psk.wedges.extend([wedge_type() for _ in range(len(object.data.loops))])
-
-            for loop_index, loop in enumerate(object.data.loops):
-                wedge = psk.wedges[wedge_offset + loop_index]
-                wedge.material_index = 0  # NOTE: this material index is set properly while building the faces
-                wedge.point_index = loop.vertex_index + vertex_offset
-                wedge.u, wedge.v = uv_layer[loop_index].uv
-                wedge.v = 1.0 - wedge.v
-                psk.wedges.append(wedge)
-
-            # MATERIALS
-            material_indices = []
-            for i, m in enumerate(object.data.materials):
-                if m is None:
-                    raise RuntimeError('Material cannot be empty (index ' + str(i) + ')')
-                if m.name in materials:
-                    material_index = list(materials.keys()).index(m.name)
-                else:
-                    material = Psk.Material()
-                    material.name = bytes(m.name, encoding='utf-8')
-                    material.texture_index = len(psk.materials)
-                    psk.materials.append(material)
-                    materials[m.name] = m
-                    material_index = material.texture_index
-                material_indices.append(material_index)
-
-            # FACES
-            # TODO: this is making the assumption that the mesh is triangulated
-            object.data.calc_loop_triangles()
-            poly_groups, groups = object.data.calc_smooth_groups(use_bitflags=True)
-            for f in object.data.loop_triangles:
-                face = Psk.Face()
-                face.material_index = material_indices[f.material_index]
-                face.wedge_index_1 = f.loops[2] + wedge_offset
-                face.wedge_index_2 = f.loops[1] + wedge_offset
-                face.wedge_index_3 = f.loops[0] + wedge_offset
-                face.smoothing_groups = poly_groups[f.polygon_index]
-                psk.faces.append(face)
-                # update the material index of the wedges
-                for i in range(3):
-                    psk.wedges[wedge_offset + f.loops[i]].material_index = face.material_index
-
-            # WEIGHTS
-            # TODO: bone ~> vg might not be 1:1, provide a nice error message if this is the case
-            armature = input_objects.armature_object.data
-            bone_names = [x.name for x in armature.bones]
-            vertex_group_names = [x.name for x in object.vertex_groups]
-            bone_indices = [bone_names.index(name) for name in vertex_group_names]
-            for vertex_group_index, vertex_group in enumerate(object.vertex_groups):
-                bone_index = bone_indices[vertex_group_index]
-                for vertex_index in range(len(object.data.vertices)):
-                    try:
-                        weight = vertex_group.weight(vertex_index)
-                    except RuntimeError:
-                        continue
-                    if weight == 0.0:
-                        continue
-                    w = Psk.Weight()
-                    w.bone_index = bone_index
-                    w.point_index = vertex_offset + vertex_index
-                    w.weight = weight
-                    psk.weights.append(w)
-
-            vertex_offset += len(psk.points)
-            wedge_offset += len(psk.wedges)
-            weight_offset += len(psk.weights)
-
-        return psk

io_export_psk_psa/psk/data.py

@@ -1,72 +0,0 @@
-from typing import List
-from ..data import *
-
-
-class Psk(object):
-
-    class Wedge16(Structure):
-        _fields_ = [
-            ('point_index', c_int16),
-            ('padding1', c_int16),
-            ('u', c_float),
-            ('v', c_float),
-            ('material_index', c_int8),
-            ('reserved', c_int8),
-            ('padding2', c_int16)
-        ]
-
-    class Wedge32(Structure):
-        _fields_ = [
-            ('point_index', c_int32),
-            ('u', c_float),
-            ('v', c_float),
-            ('material_index', c_int32)
-        ]
-
-    class Face(Structure):
-        _fields_ = [
-            ('wedge_index_1', c_int16),
-            ('wedge_index_2', c_int16),
-            ('wedge_index_3', c_int16),
-            ('material_index', c_int8),
-            ('aux_material_index', c_int8),
-            ('smoothing_groups', c_int32)
-        ]
-
-    class Material(Structure):
-        _fields_ = [
-            ('name', c_char * 64),
-            ('texture_index', c_int32),
-            ('poly_flags', c_int32),
-            ('aux_material', c_int32),
-            ('aux_flags', c_int32),
-            ('lod_bias', c_int32),
-            ('lod_style', c_int32)
-        ]
-
-    class Bone(Structure):
-        _fields_ = [
-            ('name', c_char * 64),
-            ('flags', c_int32),
-            ('children_count', c_int32),
-            ('parent_index', c_int32),
-            ('rotation', Quaternion),
-            ('location', Vector3),
-            ('length', c_float),
-            ('size', Vector3)
-        ]
-
-    class Weight(Structure):
-        _fields_ = [
-            ('weight', c_float),
-            ('point_index', c_int32),
-            ('bone_index', c_int32),
-        ]
-
-    def __init__(self):
-        self.points: List[Vector3] = []
-        self.wedges: List[Psk.Wedge16] = []
-        self.faces: List[Psk.Face] = []
-        self.materials: List[Psk.Material] = []
-        self.weights: List[Psk.Weight] = []
-        self.bones: List[Psk.Bone] = []

io_export_psk_psa/psk/exporter.py

@@ -1,38 +0,0 @@
-from typing import Type
-from .data import *
-
-
-class PskExporter(object):
-    def __init__(self, psk: Psk):
-        self.psk: Psk = psk
-
-    @staticmethod
-    def write_section(fp, name: bytes, data_type: Type[Structure] = None, data: list = None):
-        section = Section()
-        section.name = name
-        if data_type is not None and data is not None:
-            section.data_size = sizeof(data_type)
-            section.data_count = len(data)
-        fp.write(section)
-        if data is not None:
-            for datum in data:
-                fp.write(datum)
-
-    def export(self, path: str):
-        # TODO: add logic somewhere to assert lengths of ctype structs
-        with open(path, 'wb') as fp:
-            self.write_section(fp, b'ACTRHEAD')
-            self.write_section(fp, b'PNTS0000', Vector3, self.psk.points)
-
-            # WEDGES
-            # TODO: this really should be on the level of the builder, not the exporter
-            if len(self.psk.wedges) <= 65536:
-                wedge_type = Psk.Wedge16
-            else:
-                wedge_type = Psk.Wedge32
-
-            self.write_section(fp, b'VTXW0000', wedge_type, self.psk.wedges)
-            self.write_section(fp, b'FACE0000', Psk.Face, self.psk.faces)
-            self.write_section(fp, b'MATT0000', Psk.Material, self.psk.materials)
-            self.write_section(fp, b'REFSKELT', Psk.Bone, self.psk.bones)
-            self.write_section(fp, b'RAWWEIGHTS', Psk.Weight, self.psk.weights)

io_export_psk_psa/psk/operator.py

@@ -1,36 +0,0 @@
-from bpy.types import Operator
-from bpy_extras.io_utils import ExportHelper
-from bpy.props import StringProperty, BoolProperty, FloatProperty
-from .builder import PskBuilder
-from .exporter import PskExporter
-
-
-class PskExportOperator(Operator, ExportHelper):
-    bl_idname = 'export.psk'
-    bl_label = 'Export'
-    __doc__ = 'PSK Exporter (.psk)'
-    filename_ext = '.psk'
-    filter_glob: StringProperty(default='*.psk', options={'HIDDEN'})
-
-    filepath: StringProperty(
-        name='File Path',
-        description='File path used for exporting the PSK file',
-        maxlen=1024,
-        default='')
-
-    def invoke(self, context, event):
-        try:
-            PskBuilder.get_input_objects(context)
-        except RuntimeError as e:
-            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
-            return {'CANCELLED'}
-
-        context.window_manager.fileselect_add(self)
-        return {'RUNNING_MODAL'}
-
-    def execute(self, context):
-        builder = PskBuilder()
-        psk = builder.build(context)
-        exporter = PskExporter(psk)
-        exporter.export(self.filepath)
-        return {'FINISHED'}

io_scene_psk_psa/__init__.py

@@ -0,0 +1,140 @@
+from .shared import (
+    types as shared_types,
+    helpers as shared_helpers,
+    dfs as shared_dfs,
+    ui as shared_ui,
+    operators as shared_operators,
+)
+from .psk import (
+    builder as psk_builder,
+    importer as psk_importer,
+    properties as psk_properties,
+    ui as psk_ui,
+) 
+from .psk.export import (
+    operators as psk_export_operators,
+    properties as psk_export_properties,
+    ui as psk_export_ui,
+)
+from .psk.import_ import (
+    operators as psk_import_operators,
+)
+from .psa import (
+    config as psa_config,
+    builder as psa_builder,
+    importer as psa_importer,
+    file_handlers as psa_file_handlers,
+)
+from .psa.export import (
+    properties as psa_export_properties,
+    ui as psa_export_ui,
+    operators as psa_export_operators,
+)
+from .psa.import_ import (
+    operators as psa_import_operators,
+    ui as psa_import_ui,
+    properties as psa_import_properties,
+)
+
+_needs_reload = 'bpy' in locals()
+
+if _needs_reload:
+    import importlib
+
+    importlib.reload(shared_helpers)
+    importlib.reload(shared_types)
+    importlib.reload(shared_dfs)
+    importlib.reload(shared_ui)
+    importlib.reload(shared_operators)
+
+    importlib.reload(psk_builder)
+    importlib.reload(psk_importer)
+    importlib.reload(psk_properties)
+    importlib.reload(psk_ui)
+    importlib.reload(psk_export_properties)
+    importlib.reload(psk_export_operators)
+    importlib.reload(psk_export_ui)
+    importlib.reload(psk_import_operators)
+
+    importlib.reload(psa_config)
+    importlib.reload(psa_builder)
+    importlib.reload(psa_importer)
+    importlib.reload(psa_export_properties)
+    importlib.reload(psa_export_operators)
+    importlib.reload(psa_export_ui)
+    importlib.reload(psa_import_properties)
+    importlib.reload(psa_import_operators)
+    importlib.reload(psa_import_ui)
+    importlib.reload(psa_file_handlers)
+
+import bpy
+from bpy.props import PointerProperty
+
+
+def psk_export_menu_func(self, context):
+    self.layout.operator(psk_export_operators.PSK_OT_export.bl_idname, text='Unreal PSK (.psk)')
+
+
+def psk_import_menu_func(self, context):
+    self.layout.operator(psk_import_operators.PSK_OT_import.bl_idname, text='Unreal PSK (.psk/.pskx)')
+
+
+def psa_export_menu_func(self, context):
+    self.layout.operator(psa_export_operators.PSA_OT_export.bl_idname, text='Unreal PSA (.psa)')
+
+
+def psa_import_menu_func(self, context):
+    self.layout.operator(psa_import_operators.PSA_OT_import.bl_idname, text='Unreal PSA (.psa)')
+
+
+_modules = (
+    shared_types,
+    shared_ui,
+    shared_operators,
+    psk_properties,
+    psk_ui,
+    psk_import_operators,
+    psk_export_properties,
+    psk_export_operators,
+    psk_export_ui,
+    psa_export_properties,
+    psa_export_operators,
+    psa_export_ui,
+    psa_import_properties,
+    psa_import_operators,
+    psa_import_ui,
+    psa_file_handlers,
+)
+
+def register():
+    for module in _modules:
+        module.register()
+    bpy.types.TOPBAR_MT_file_export.append(psk_export_menu_func)
+    bpy.types.TOPBAR_MT_file_import.append(psk_import_menu_func)
+    bpy.types.TOPBAR_MT_file_export.append(psa_export_menu_func)
+    bpy.types.TOPBAR_MT_file_import.append(psa_import_menu_func)
+    setattr(bpy.types.Material, 'psk', PointerProperty(type=psk_properties.PSX_PG_material, options={'HIDDEN'}))
+    setattr(bpy.types.Scene, 'psx_export', PointerProperty(type=shared_types.PSX_PG_scene_export, options={'HIDDEN'}))
+    setattr(bpy.types.Scene, 'psa_import', PointerProperty(type=psa_import_properties.PSA_PG_import, options={'HIDDEN'}))
+    setattr(bpy.types.Scene, 'psa_export', PointerProperty(type=psa_export_properties.PSA_PG_export, options={'HIDDEN'}))
+    setattr(bpy.types.Scene, 'psk_export', PointerProperty(type=psk_export_properties.PSK_PG_export, options={'HIDDEN'}))
+    setattr(bpy.types.Action, 'psa_export', PointerProperty(type=shared_types.PSX_PG_action_export, options={'HIDDEN'}))
+
+
+def unregister():
+    delattr(bpy.types.Material, 'psk')
+    delattr(bpy.types.Scene, 'psx_export')
+    delattr(bpy.types.Scene, 'psa_import')
+    delattr(bpy.types.Scene, 'psa_export')
+    delattr(bpy.types.Scene, 'psk_export')
+    delattr(bpy.types.Action, 'psa_export')
+    bpy.types.TOPBAR_MT_file_export.remove(psk_export_menu_func)
+    bpy.types.TOPBAR_MT_file_import.remove(psk_import_menu_func)
+    bpy.types.TOPBAR_MT_file_export.remove(psa_export_menu_func)
+    bpy.types.TOPBAR_MT_file_import.remove(psa_import_menu_func)
+    for module in reversed(_modules):
+        module.unregister()
+
+
+if __name__ == '__main__':
+    register()

io_scene_psk_psa/blender_manifest.toml

@@ -0,0 +1,30 @@
+schema_version = "1.0.0"
+id = "io_scene_psk_psa"
+version = "9.1.1"
+name = "Unreal PSK/PSA (.psk/.psa)"
+tagline = "Import and export PSK and PSA files used in Unreal Engine"
+maintainer = "Colin Basnett <cmbasnett@gmail.com>"
+type = "add-on"
+website = "https://github.com/DarklightGames/io_scene_psk_psa/"
+tags = ["Game Engine", "Import-Export"]
+blender_version_min = "5.0.0"
+# Optional: maximum supported Blender version
+# blender_version_max = "5.1.0"
+license = [
+  "SPDX:GPL-3.0-or-later",
+]
+wheels = [
+  './wheels/psk_psa_py-0.0.4-py3-none-any.whl'
+]
+
+[build]
+paths_exclude_pattern = [
+  "/.git/",
+  "__pycache__/",
+  "/venv/",
+  "/.github/",
+  ".gitignore",
+]
+
+[permissions]
+files = "Read and write PSK and PSA files from and to disk"

io_scene_psk_psa/psa/builder.py

@@ -0,0 +1,378 @@
+from bpy.types import Action, AnimData, Context, Object, PoseBone
+
+from psk_psa_py.psa.data import Psa
+from typing import Tuple
+from mathutils import Matrix, Quaternion, Vector
+
+from ..shared.helpers import PsxBoneCollection, convert_bpy_quaternion_to_psx_quaternion, convert_vector_to_vector3, create_psx_bones, get_coordinate_system_transform
+
+
+class PsaBuildSequence:
+    class NlaState:
+        def __init__(self):
+            self.action: Action | None = None
+            self.frame_start: int = 0
+            self.frame_end: int = 0
+
+    def __init__(self, armature_object: Object, anim_data: AnimData):
+        self.armature_object = armature_object
+        self.anim_data = anim_data
+        self.name: str = ''
+        self.nla_state: PsaBuildSequence.NlaState = PsaBuildSequence.NlaState()
+        self.compression_ratio: float = 1.0
+        self.key_quota: int = 0
+        self.fps: float = 30.0
+        self.group: str | None = None
+
+
+class PsaBuildOptions:
+    def __init__(self):
+        self.armature_objects: list[Object] = []
+        self.animation_data: AnimData | None = None
+        self.sequences: list[PsaBuildSequence] = []
+        self.bone_filter_mode: str = 'ALL'
+        self.bone_collection_indices: list[PsxBoneCollection] = []
+        self.sequence_name_prefix: str = ''
+        self.sequence_name_suffix: str = ''
+        self.scale = 1.0
+        self.sampling_mode: str = 'INTERPOLATED'  # One of ('INTERPOLATED', 'SUBFRAME')
+        self.export_space = 'WORLD'
+        self.forward_axis = 'X'
+        self.up_axis = 'Z'
+        self.sequence_source = 'ACTIONS'  # One of ('ACTIONS', 'TIMELINE_MARKERS', 'NLA_STRIPS')
+    
+    @property
+    def bone_collection_primary_key(self) -> str:
+        return 'DATA' if self.sequence_source == 'ACTIVE_ACTION' else 'OBJECT'
+
+
+class PsaExportBone:
+    def __init__(self,
+                    pose_bone: PoseBone | None,
+                    armature_object: Object | None,
+                    scale: Vector):
+        self.pose_bone = pose_bone
+        self.armature_object = armature_object
+        self.scale = scale
+    
+    @property
+    def is_armature_root_bone(self) -> bool:
+        return self.pose_bone is not None and self.pose_bone.parent is None
+    
+    @property
+    def is_attached_to_armature(self) -> bool:
+        return self.get_attached_armature() is not None
+    
+    def get_attached_armature(self) -> tuple[Object, PoseBone] | None:
+        if not self.is_armature_root_bone:
+            return None
+        assert self.armature_object is not None
+        match self.armature_object.parent_type:
+            case 'BONE':
+                parent_bone_name = self.armature_object.parent_bone
+                assert self.armature_object.parent is not None
+                parent_armature_object = self.armature_object.parent
+                assert parent_armature_object.pose is not None
+                parent_pose_bone = parent_armature_object.pose.bones.get(parent_bone_name)
+                if parent_pose_bone is None:
+                    return None
+                return (parent_armature_object, parent_pose_bone)
+            case _:
+                return None
+    
+    def get_attached_armature_transform(self) -> Matrix:
+        attached_armature, attached_pose_bone = self.get_attached_armature() or (None, None)
+        if attached_armature is None or attached_pose_bone is None:
+            return Matrix.Identity(4)
+        if attached_pose_bone.parent is not None:
+            attached_bone_matrix = attached_pose_bone.parent.matrix.inverted() @ attached_pose_bone.matrix
+        else:
+            attached_bone_matrix = attached_armature.matrix_world @ attached_pose_bone.matrix
+        return attached_bone_matrix
+
+def _get_pose_bone_location_and_rotation(
+    pose_bone: PoseBone,
+    armature_object: Object,
+    export_bone: PsaExportBone,
+    export_space: str,
+    scale: Vector,
+    coordinate_system_transform: Matrix,
+) -> Tuple[Vector, Quaternion]:
+    if pose_bone.parent is not None:
+        pose_bone_matrix = pose_bone.parent.matrix.inverted() @ pose_bone.matrix
+    else:
+        # Root bone
+        # Get the bone's pose matrix and transform it into the export space.
+        # In the case of an 'ARMATURE' export space, this will be the inverse of armature object's world matrix.
+        # Otherwise, it will be the identity matrix.
+
+        if export_bone.is_attached_to_armature:
+            # Get the world space matrix of both this bone and the bone that we're attached to,
+            # then calculate a matrix relative to the attached bone.
+            world_matrix = armature_object.matrix_world @ pose_bone.matrix
+            assert export_bone.armature_object
+            my_parent = export_bone.armature_object.parent
+            assert my_parent
+            my_parent_bone = export_bone.armature_object.parent_bone
+            assert my_parent.pose
+            parent_pose_bone = my_parent.pose.bones[my_parent_bone]
+            parent_world_matrix = my_parent.matrix_world @ parent_pose_bone.matrix
+            pose_bone_matrix = parent_world_matrix.inverted() @ world_matrix
+        else:
+            match export_space:
+                case 'ARMATURE':
+                    pose_bone_matrix = pose_bone.matrix
+                case 'WORLD':
+                    pose_bone_matrix = armature_object.matrix_world @ pose_bone.matrix
+                case 'ROOT':
+                    pose_bone_matrix = Matrix.Identity(4)
+                case _:
+                    assert False, f'Invalid export space: {export_space}'
+            # The root bone is the only bone that should be transformed by the coordinate system transform, since all
+            # other bones are relative to their parent bones.
+            pose_bone_matrix = coordinate_system_transform @ pose_bone_matrix
+
+    location = pose_bone_matrix.to_translation()
+    rotation = pose_bone_matrix.to_quaternion().normalized()
+
+    if pose_bone.parent is not None:
+        # Don't apply scale to the root bone of armatures if we have a false root.
+        # TODO: probably remove this?
+        location *= scale
+        rotation.conjugate()
+
+    return location, rotation
+
+
+def build_psa(context: Context, options: PsaBuildOptions) -> Psa:
+
+    assert context.scene
+    assert context.window_manager
+
+    psa = Psa()
+
+    armature_objects_for_bones = options.armature_objects
+    if options.sequence_source == 'ACTIVE_ACTION' and len(options.armature_objects) >= 2:
+        # Make sure that the data-block for all the selected armature objects is the same.
+        if any(map(lambda o: o.data != options.armature_objects[0].data, options.armature_objects[1:])):
+            raise RuntimeError('All armature objects must share the same data-block when exporting from the active action')
+        armature_objects_for_bones = [options.armature_objects[0]]
+
+    psx_bone_create_result = create_psx_bones(
+        armature_objects=armature_objects_for_bones,
+        export_space=options.export_space,
+        forward_axis=options.forward_axis,
+        up_axis=options.up_axis,
+        scale=options.scale,
+        bone_filter_mode=options.bone_filter_mode,
+        bone_collection_indices=options.bone_collection_indices,
+        bone_collection_primary_key=options.bone_collection_primary_key,
+    )
+
+    # Build list of PSA bones.
+    # Note that the PSA bones are just here to validate the hierarchy.
+    # The bind pose information is not used by the engine.
+    psa.bones = [bone.psx_bone for bone in psx_bone_create_result.bones]
+
+    # No bones are going to be exported.
+    if len(psa.bones) == 0:
+        raise RuntimeError('No bones available for export')
+
+    # Add prefixes and suffices to the names of the export sequences and strip whitespace.
+    for export_sequence in options.sequences:
+        export_sequence.name = f'{options.sequence_name_prefix}{export_sequence.name}{options.sequence_name_suffix}'
+        export_sequence.name = export_sequence.name.strip()
+
+    # Save each armature object's current action and frame so that we can restore the state once we are done.
+    saved_armature_object_actions = {o: (o.animation_data.action if o.animation_data else None) for o in options.armature_objects}
+    saved_frame_current = context.scene.frame_current
+
+    # Now build the PSA sequences.
+    # We actually alter the timeline frame and simply record the resultant pose bone matrices.
+    frame_start_index = 0
+
+    context.window_manager.progress_begin(0, len(options.sequences))
+
+    coordinate_system_transform = get_coordinate_system_transform(options.forward_axis, options.up_axis)
+
+    for export_sequence_index, export_sequence in enumerate(options.sequences):
+        frame_start = export_sequence.nla_state.frame_start
+        frame_end = export_sequence.nla_state.frame_end
+
+        # Calculate the frame step based on the compression factor.
+        frame_extents = abs(frame_end - frame_start)
+        frame_count_raw = frame_extents + 1
+        frame_count = max(1, max(export_sequence.key_quota, int(frame_count_raw * export_sequence.compression_ratio)))
+        frame_step = frame_extents / (frame_count - 1) if frame_count > 1 else 0.0
+
+        # If this is a reverse sequence, we need to reverse the frame step.
+        if frame_start > frame_end:
+            frame_step = -frame_step
+
+        sequence_duration = frame_count_raw / export_sequence.fps
+
+        psa_sequence = Psa.Sequence()
+        
+        try:
+            psa_sequence.name = bytes(export_sequence.name, encoding='windows-1252')
+        except UnicodeEncodeError:
+            raise RuntimeError(
+                f'Sequence name "{export_sequence.name}" contains characters that cannot be encoded in the Windows-1252 codepage')
+        
+        try:
+            if export_sequence.group is not None:
+                psa_sequence.group = bytes(export_sequence.group, encoding='windows-1252')
+        except UnicodeDecodeError:
+            raise RuntimeError(
+                f'Group name "{export_sequence.group} contains characters that cannot be encoded in the Windows-1252 codepage')
+        
+        psa_sequence.frame_count = frame_count
+        psa_sequence.frame_start_index = frame_start_index
+        psa_sequence.fps = frame_count / sequence_duration
+        psa_sequence.bone_count = len(psa.bones)
+        psa_sequence.track_time = frame_count
+        psa_sequence.key_reduction = 1.0
+
+        frame = float(frame_start)
+
+        # Link the action to the animation data and update view layer.
+        for armature_object in options.armature_objects:
+            if armature_object.animation_data:
+                armature_object.animation_data.action = export_sequence.nla_state.action
+
+        assert context.view_layer
+        context.view_layer.update()
+
+        def add_key(location: Vector, rotation: Quaternion):
+            key = Psa.Key()
+            key.location = convert_vector_to_vector3(location)
+            key.rotation = convert_bpy_quaternion_to_psx_quaternion(rotation)
+            key.time = 1.0 / psa_sequence.fps
+            psa.keys.append(key)
+
+        armature_scales: dict[Object, Vector] = {}
+
+        # Extract the scale from the world matrix of the evaluated armature object.
+        for armature_object in options.armature_objects:
+            evaluated_armature_object = armature_object.evaluated_get(context.evaluated_depsgraph_get())
+            _, _, scale = evaluated_armature_object.matrix_world.decompose()
+            scale *= options.scale
+            armature_scales[armature_object] = scale
+
+        # Create a list of export pose bones, in the same order as the bones as they appear in the armature.
+        # The object contains the pose bone, the armature object, and a pre-calculated scaling value to apply to the
+        # locations.
+        export_bones: list[PsaExportBone] = []
+
+        for bone in psx_bone_create_result.bones:
+            if bone.armature_object is None:
+                export_bone = PsaExportBone(None, None, Vector((1.0, 1.0, 1.0)))
+                export_bones.append(export_bone)
+                continue
+
+            assert bone.armature_object.pose
+            pose_bone = bone.armature_object.pose.bones[bone.psx_bone.name.decode('windows-1252')]
+
+            export_bones.append(PsaExportBone(pose_bone, bone.armature_object, armature_scales[bone.armature_object]))
+
+        match options.sampling_mode:
+            case 'INTERPOLATED':
+                # Used as a store for the last frame's pose bone locations and rotations.
+                last_frame: int | None = None
+                last_frame_bone_poses: list[tuple[Vector, Quaternion]] = []
+
+                next_frame: int | None = None
+                next_frame_bone_poses: list[tuple[Vector, Quaternion]] = []
+
+                for _ in range(frame_count):
+                    if last_frame is None or last_frame != int(frame):
+                        # Populate the bone poses for frame A.
+                        last_frame = int(frame)
+
+                        # TODO: simplify this code and make it easier to follow!
+                        if next_frame == last_frame:
+                            # Simply transfer the data from next_frame to the last_frame so that we don't need to
+                            # resample anything.
+                            last_frame_bone_poses = next_frame_bone_poses.copy()
+                        else:
+                            last_frame_bone_poses.clear()
+                            context.scene.frame_set(frame=last_frame)
+                            for export_bone in export_bones:
+                                location, rotation = _get_pose_bone_location_and_rotation(
+                                    export_bone.pose_bone,
+                                    export_bone.armature_object,
+                                    export_bone,
+                                    options.export_space,
+                                    export_bone.scale,
+                                    coordinate_system_transform=coordinate_system_transform
+                                )
+                                last_frame_bone_poses.append((location, rotation))
+
+                        next_frame = None
+                        next_frame_bone_poses.clear()
+
+                    # If this is not a subframe, just use the last frame's bone poses.
+                    if frame % 1.0 == 0:
+                        for i in range(len(export_bones)):
+                            add_key(*last_frame_bone_poses[i])
+                    else:
+                        # Otherwise, this is a subframe, so we need to interpolate the pose between the next frame and the last frame.
+                        if next_frame is None:
+                            next_frame = last_frame + 1
+                            context.scene.frame_set(frame=next_frame)
+                            for export_bone in export_bones:
+                                location, rotation = _get_pose_bone_location_and_rotation(
+                                    pose_bone=export_bone.pose_bone,
+                                    armature_object=export_bone.armature_object,
+                                    export_bone=export_bone,
+                                    export_space=options.export_space,
+                                    scale=export_bone.scale,
+                                    coordinate_system_transform=coordinate_system_transform,
+                                )
+                                next_frame_bone_poses.append((location, rotation))
+
+                        factor = frame % 1.0
+
+                        for i in range(len(export_bones)):
+                            last_location, last_rotation = last_frame_bone_poses[i]
+                            next_location, next_rotation = next_frame_bone_poses[i]
+
+                            location = last_location.lerp(next_location, factor)
+                            rotation = last_rotation.slerp(next_rotation, factor)
+
+                            add_key(location, rotation)
+
+                    frame += frame_step
+            case 'SUBFRAME':
+                for _ in range(frame_count):
+                    context.scene.frame_set(frame=int(frame), subframe=frame % 1.0)
+
+                    for export_bone in export_bones:
+                        location, rotation = _get_pose_bone_location_and_rotation(
+                            pose_bone=export_bone.pose_bone,
+                            armature_object=export_bone.armature_object,
+                            export_bone=export_bone,
+                            export_space=options.export_space,
+                            scale=export_bone.scale,
+                            coordinate_system_transform=coordinate_system_transform,
+                        )
+                        add_key(location, rotation)
+
+                    frame += frame_step
+
+        frame_start_index += frame_count
+
+        psa.sequences[export_sequence.name] = psa_sequence
+
+        context.window_manager.progress_update(export_sequence_index)
+
+    # Restore the previous actions & frame.
+    for armature_object, action in saved_armature_object_actions.items():
+        assert armature_object.animation_data
+        armature_object.animation_data.action = action
+
+    context.scene.frame_set(saved_frame_current)
+
+    context.window_manager.progress_end()
+
+    return psa

io_scene_psk_psa/psa/config.py

@@ -0,0 +1,76 @@
+import re
+from configparser import ConfigParser
+
+REMOVE_TRACK_LOCATION = (1 << 0)
+REMOVE_TRACK_ROTATION = (1 << 1)
+
+
+class PsaConfig:
+    def __init__(self):
+        self.sequence_bone_flags: dict[str, dict[int, int]] = dict()
+
+
+def _load_config_file(file_path: str) -> ConfigParser:
+    """
+    UEViewer exports a dialect of INI files that is not compatible with Python's ConfigParser.
+    Specifically, it allows values in this format:
+
+    [Section]
+    Key1
+    Key2
+
+    This is not allowed in Python's ConfigParser, which requires a '=' character after each key name.
+    To work around this, we'll modify the file to add the '=' character after each key name if it is missing.
+    """
+    with open(file_path, 'r') as f:
+        lines = f.read().split('\n')
+
+    lines = [re.sub(r'^\s*([^=]+)\s*$', r'\1=', line) for line in lines]
+
+    contents = '\n'.join(lines)
+
+    config = ConfigParser()
+    config.read_string(contents)
+
+    return config
+
+
+def _get_bone_flags_from_value(value: str) -> int:
+    match value:
+        case 'all':
+            return REMOVE_TRACK_LOCATION | REMOVE_TRACK_ROTATION
+        case 'trans':
+            return REMOVE_TRACK_LOCATION
+        case 'rot':
+            return REMOVE_TRACK_ROTATION
+        case _:
+            return 0
+
+
+def read_psa_config(psa_sequence_names: list[str], file_path: str) -> PsaConfig:
+    psa_config = PsaConfig()
+
+    config = _load_config_file(file_path)
+
+    if config.has_section('RemoveTracks'):
+        for key, value in config.items('RemoveTracks'):
+            match = re.match(rf'^(.+)\.(\d+)$', key)
+            if not match:
+                continue
+            sequence_name = match.group(1)
+
+            # Map the sequence name onto the actual sequence name in the PSA file.
+            try:
+                lowercase_sequence_names = [sequence_name.lower() for sequence_name in psa_sequence_names]
+                sequence_name = psa_sequence_names[lowercase_sequence_names.index(sequence_name.lower())]
+            except ValueError:
+                # Sequence name is not in the PSA file.
+                continue
+
+            if sequence_name not in psa_config.sequence_bone_flags:
+                psa_config.sequence_bone_flags[sequence_name] = dict()
+
+            bone_index = int(match.group(2))
+            psa_config.sequence_bone_flags[sequence_name][bone_index] = _get_bone_flags_from_value(value)
+
+    return psa_config

io_scene_psk_psa/psa/export/operators.py

@@ -0,0 +1,882 @@
+from abc import abstractmethod
+from collections import Counter
+from typing import Iterable, Sequence, Tuple, cast as typing_cast
+
+import bpy
+import re
+from bpy.props import StringProperty
+from bpy.types import Context, Action, Object, AnimData, TimelineMarker, Operator, Armature, UILayout, Scene, ActionKeyframeStrip
+from bpy_extras.io_utils import ExportHelper
+
+from .properties import (
+    PSA_PG_export,
+    PsaExportMixin,
+    PsaExportSequenceMixin,
+    filter_sequences,
+    get_sequences_from_name_and_frame_range,
+)
+from .ui import PSA_UL_export_sequences
+from ..builder import build_psa, PsaBuildSequence, PsaBuildOptions
+from psk_psa_py.psa.writer import write_psa_to_file
+from ...shared.helpers import get_collection_export_operator_from_context, get_collection_from_context, get_psk_input_objects_for_collection, populate_bone_collection_list, get_nla_strips_in_frame_range, PsxBoneCollection
+from ...shared.types import PSX_PG_action_export
+from ...shared.ui import draw_bone_filter_mode
+from ...shared.operators import PSK_OT_bone_collection_list_populate, PSK_OT_bone_collection_list_select_all
+
+
+def get_sequences_propnames_from_source(sequence_source: str) -> Tuple[str, str]:
+    match sequence_source:
+        case 'ACTIONS':
+            return 'action_list', 'action_list_index'
+        case 'TIMELINE_MARKERS':
+            return 'marker_list', 'marker_list_index'
+        case 'NLA_TRACK_STRIPS':
+            return 'nla_strip_list', 'nla_strip_list_index'
+        case 'ACTIVE_ACTION':
+            return 'active_action_list', 'active_action_list_index'
+        case _:
+            assert False, f'Invalid sequence source: {sequence_source}'
+
+
+def is_action_for_object(obj: Object, action: Action):
+    if len(action.layers) == 0:
+        return False
+
+    if obj is None or obj.animation_data is None or obj.type != 'ARMATURE':
+        return False
+
+    armature_data = typing_cast(Armature, obj.data)
+    bone_names = set([x.name for x in armature_data.bones])
+
+    # The nesting here is absolutely bonkers.
+    for layer in action.layers:
+        for strip in layer.strips:
+            if not isinstance(strip, ActionKeyframeStrip):
+                continue
+            for channelbag in strip.channelbags:
+                for fcurve in channelbag.fcurves:
+                    match = re.match(r'pose\.bones\[\"([^\"]+)\"](\[\"([^\"]+)\"])?', fcurve.data_path)
+                    if not match:
+                        continue
+                    bone_name = match.group(1)
+                    if bone_name in bone_names:
+                        return True
+    
+    return False
+
+
+def update_actions_and_timeline_markers(context: Context, armature_objects: Sequence[Object], pg: PsaExportMixin):
+    assert context.scene is not None
+
+    # Clear actions and markers.
+    pg.action_list.clear()
+    pg.marker_list.clear()
+    pg.active_action_list.clear()
+
+    # TODO: this is cleared in the callback, although this should probably be changed.
+    # pg.nla_strip_list.clear()
+    
+    assert len(armature_objects) >= 0, 'Must have at least one armature object'
+
+    # TODO: for now, use the first armature object's animation data.
+    # animation_data_object = get_animation_data_object(context, pg)
+    armature_object = armature_objects[0]
+    animation_data = armature_object.animation_data if armature_object else None
+
+    if animation_data is None:
+        return
+
+    # Populate actions list.
+    for action in bpy.data.actions:
+        if not any(map(lambda armature_object: is_action_for_object(armature_object, action), armature_objects)):
+            # This action is not applicable to any of the selected armatures.
+            continue
+
+        for (name, frame_start, frame_end) in get_sequences_from_action(action):
+            item = pg.action_list.add()
+            item.action_name = action.name
+            item.name = name
+            item.is_selected = False
+            item.is_pose_marker = False
+            item.frame_start = frame_start
+            item.frame_end = frame_end
+
+        # Pose markers are not guaranteed to be in frame-order, so make sure that they are.
+        pose_markers = sorted(action.pose_markers, key=lambda x: x.frame)
+        for pose_marker_index, pose_marker in enumerate(pose_markers):
+            sequences = get_sequences_from_action_pose_markers(action, pose_markers, pose_marker, pose_marker_index)
+            for (name, frame_start, frame_end) in sequences:
+                item = pg.action_list.add()
+                item.action_name = action.name
+                item.name = name
+                item.is_selected = False
+                item.is_pose_marker = True
+                item.frame_start = frame_start
+                item.frame_end = frame_end
+
+    # Populate timeline markers list.
+    marker_names = [x.name for x in context.scene.timeline_markers]
+    sequence_frame_ranges = get_timeline_marker_sequence_frame_ranges(animation_data, context.scene, marker_names)
+
+    for marker_name in marker_names:
+        if marker_name not in sequence_frame_ranges:
+            continue
+        if marker_name.strip() == '' or marker_name.startswith('#'):
+            continue
+        frame_start, frame_end = sequence_frame_ranges[marker_name]
+        sequences = get_sequences_from_name_and_frame_range(marker_name, frame_start, frame_end)
+        for (sequence_name, frame_start, frame_end) in sequences:
+            item = pg.marker_list.add()
+            item.name = sequence_name
+            item.is_selected = False
+            item.frame_start = frame_start
+            item.frame_end = frame_end
+
+    # Populate the active action list.
+    for armature_object in armature_objects:
+        active_action = armature_object.animation_data.action if armature_object.animation_data else None
+        if active_action is None:
+            continue
+        sequences = get_sequences_from_action(active_action)
+        for (sequence_name, frame_start, frame_end) in sequences:
+            # TODO: for some reason we aren't doing the sequence name parsing here.
+            item = pg.active_action_list.add()
+            item.name = sequence_name
+            item.armature_object_name = armature_object.name
+            item.action_name = active_action.name
+            item.frame_start = frame_start
+            item.frame_end = frame_end
+            item.is_selected = True
+
+
+def get_sequence_fps(context: Context, fps_source: str, fps_custom: float, actions: Iterable[Action]) -> float:
+    match fps_source:
+        case 'SCENE':
+            assert context.scene
+            return context.scene.render.fps
+        case 'CUSTOM':
+            return fps_custom
+        case 'ACTION_METADATA':
+            # Get the minimum value of action metadata FPS values.
+            return min([typing_cast(PSX_PG_action_export, getattr(action, 'psa_export')).fps for action in actions])
+        case _:
+            assert False, f'Invalid FPS source: {fps_source}'
+
+
+def get_sequence_compression_ratio(
+        compression_ratio_source: str, 
+        compression_ratio_custom: float, 
+        actions: Iterable[Action],
+        ) -> float:
+    match compression_ratio_source:
+        case 'ACTION_METADATA':
+            # Get the minimum value of action metadata compression ratio values.
+            return min(map(lambda action: typing_cast(PSX_PG_action_export, getattr(action, 'psa_export')).compression_ratio, actions))
+        case 'CUSTOM':
+            return compression_ratio_custom
+        case _:
+            assert False, f'Invalid compression ratio source: {compression_ratio_source}'
+
+
+def get_timeline_marker_sequence_frame_ranges(
+        animation_data: AnimData, 
+        scene: Scene,
+        marker_names: list[str],
+        ) -> dict[str, tuple[int, int]]:
+    # Timeline markers need to be sorted so that we can determine the sequence start and end positions.
+    sequence_frame_ranges: dict[str, tuple[int, int]] = dict()
+    sorted_timeline_markers = list(sorted(scene.timeline_markers, key=lambda x: x.frame))
+    sorted_timeline_marker_names = [x.name for x in sorted_timeline_markers]
+
+    for marker_name in marker_names:
+        marker = scene.timeline_markers[marker_name]
+        frame_start = marker.frame
+        # Determine the final frame of the sequence based on the next marker.
+        # If no subsequent marker exists, use the maximum frame_end from all NLA strips.
+        marker_index = sorted_timeline_marker_names.index(marker_name)
+        next_marker_index = marker_index + 1
+        frame_end = 0
+        if next_marker_index < len(sorted_timeline_markers):
+            # There is a next marker. Use that next marker's frame position as the last frame of this sequence.
+            frame_end = sorted_timeline_markers[next_marker_index].frame
+            nla_strips = list(get_nla_strips_in_frame_range(animation_data, marker.frame, frame_end))
+            if len(nla_strips) > 0:
+                frame_end = min(frame_end, max(map(lambda nla_strip: nla_strip.frame_end, nla_strips)))
+                frame_start = max(frame_start, min(map(lambda nla_strip: nla_strip.frame_start, nla_strips)))
+            else:
+                # No strips in between this marker and the next, just export this as a one-frame animation.
+                frame_end = frame_start
+        else:
+            # There is no next marker.
+            # Find the final frame of all the NLA strips and use that as the last frame of this sequence.
+            for nla_track in animation_data.nla_tracks:
+                if nla_track.mute:
+                    continue
+                for strip in nla_track.strips:
+                    frame_end = max(frame_end, strip.frame_end)
+
+        if frame_start > frame_end:
+            continue
+
+        sequence_frame_ranges[marker_name] = int(frame_start), int(frame_end)
+
+    return sequence_frame_ranges
+
+
+def get_sequences_from_action(action: Action):
+    if action.name == '' or action.name.startswith('#'):
+        return
+
+    frame_start = int(action.frame_range[0])
+    action_name = action.name
+
+    if action_name.startswith('!'):
+        # If the pose marker name starts with an exclamation mark, only export the first frame.
+        frame_end = frame_start
+        action_name = action_name[1:]
+    else:
+        frame_end = int(action.frame_range[1])
+
+    yield from get_sequences_from_name_and_frame_range(action_name, frame_start, frame_end)
+
+
+def get_sequences_from_action_pose_markers(
+        action: Action, 
+        pose_markers: list[TimelineMarker], 
+        pose_marker: TimelineMarker, 
+        pose_marker_index: int,
+        ):
+    frame_start = pose_marker.frame
+    sequence_name = pose_marker.name
+    if pose_marker.name.strip() == '' or pose_marker.name.startswith('#'):
+        return
+    if pose_marker.name.startswith('!'):
+        # If the pose marker name starts with an exclamation mark, only export the first frame.
+        frame_end = frame_start
+        sequence_name = sequence_name[1:]
+    elif pose_marker_index + 1 < len(pose_markers):
+        frame_end = pose_markers[pose_marker_index + 1].frame
+    else:
+        frame_end = int(action.frame_range[1])
+    yield from get_sequences_from_name_and_frame_range(sequence_name, frame_start, frame_end)
+
+
+def get_visible_sequences(pg: PsaExportMixin, sequences) -> list[PsaExportSequenceMixin]:
+    visible_sequences = []
+    for i, flag in enumerate(filter_sequences(pg, sequences)):
+        if bool(flag & (1 << 30)):
+            visible_sequences.append(sequences[i])
+    return visible_sequences
+
+
+
+class PSA_OT_export_collection(Operator, ExportHelper, PsaExportMixin):
+    bl_idname = 'psa.export_collection'
+    bl_label = 'Export'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Export actions to PSA'
+    filename_ext = '.psa'
+    filter_glob: StringProperty(default='*.psa', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for exporting the PSA file',
+        maxlen=1024,
+        default='')
+
+    def execute(self, context: Context):
+        # TODO: get the armature objects from the collection export operator
+        collection = get_collection_from_context(context)
+        if collection is None:
+            self.report({'ERROR'}, 'No collection found for export')
+            return {'CANCELLED'}
+
+        try:
+            import_objects = get_psk_input_objects_for_collection(collection)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        options = create_psa_export_options(context, import_objects.armature_objects, self)
+
+        if len(options.sequences) == 0:
+            self.report({'ERROR'}, 'No sequences were selected for export')
+            return {'CANCELLED'}
+
+        try:
+            psa = build_psa(context, options)
+            self.report({'INFO'}, f'PSA export successful')
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        write_psa_to_file(psa, self.filepath)
+
+        return {'FINISHED'}
+
+    def draw(self, context: Context):
+        layout = self.layout
+
+        assert layout is not None
+
+        flow = layout.grid_flow(row_major=True)
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+
+        # Sequences
+        draw_sequences_panel(layout, self,
+                             PSA_OT_export_collection_sequences_select_all.bl_idname,
+                             PSA_OT_export_collection_sequences_deselect_all.bl_idname,
+                             )
+
+        # Bones
+        bones_header, bones_panel = layout.panel('Bones', default_closed=False)
+        bones_header.label(text='Bones', icon='BONE_DATA')
+        if bones_panel:
+            draw_bone_filter_mode(bones_panel, self, True)
+
+            if self.bone_filter_mode == 'BONE_COLLECTIONS':
+                row = bones_panel.row()
+                rows = max(3, min(len(self.bone_collection_list), 10))
+                row.template_list('PSX_UL_bone_collection_list', '', self, 'bone_collection_list', self, 'bone_collection_list_index', rows=rows)
+                col = row.column(align=True)
+                col.operator(PSK_OT_bone_collection_list_populate.bl_idname, text='', icon='FILE_REFRESH')
+                col.separator()
+                op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_HLT')
+                op.is_selected = True
+                op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_DEHLT')
+                op.is_selected = False
+
+        # Transform
+        transform_header, transform_panel = layout.panel('Transform', default_closed=False)
+        transform_header.label(text='Transform', icon='DRIVER_TRANSFORM')
+        if transform_panel:
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(self, 'export_space')
+            flow.prop(self, 'transform_source')
+
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+
+            match self.transform_source:
+                case 'SCENE':
+                    transform_source = getattr(context.scene, 'psx_export')
+                    flow.enabled = False
+                case 'CUSTOM':
+                    transform_source = self
+                case _:
+                    assert False, f'Invalid transform source: {self.transform_source}'
+        
+            flow.prop(transform_source, 'scale')
+            flow.prop(transform_source, 'forward_axis')
+            flow.prop(transform_source, 'up_axis')
+
+
+def draw_sequences_panel(
+        layout: UILayout, 
+        pg: PsaExportMixin,
+        sequences_select_all_operator_idname: str,
+        sequences_deselect_all_operator_idname: str,
+        ):
+    sequences_header, sequences_panel = layout.panel('Sequences', default_closed=False)
+    sequences_header.label(text='Sequences', icon='ACTION')
+
+    if sequences_panel:
+        sequences_panel.operator(PSA_OT_export_collection_populate_sequences.bl_idname, text='Refresh', icon='FILE_REFRESH')
+
+        flow = sequences_panel.grid_flow()
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+        flow.prop(pg, 'sequence_source', text='Source')
+
+        if pg.sequence_source == 'NLA_TRACK_STRIPS':
+            flow = sequences_panel.grid_flow()
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'nla_track')
+
+        # SELECT ALL/NONE
+        row = sequences_panel.row(align=True)
+        row.label(text='Select')
+        row.operator(sequences_select_all_operator_idname, text='All', icon='CHECKBOX_HLT')
+        row.operator(sequences_deselect_all_operator_idname, text='None', icon='CHECKBOX_DEHLT')
+
+        propname, active_propname = get_sequences_propnames_from_source(pg.sequence_source)
+        sequences_panel.template_list(PSA_UL_export_sequences.bl_idname, '', pg, propname, pg, active_propname,
+                                        rows=max(3, min(len(getattr(pg, propname)), 10)))
+
+        name_header, name_panel = sequences_panel.panel('Name', default_closed=False)
+        name_header.label(text='Name')
+        if name_panel:
+            flow = name_panel.grid_flow()
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'sequence_name_prefix', text='Name Prefix')
+            flow.prop(pg, 'sequence_name_suffix')
+
+            # Determine if there is going to be a naming conflict and display an error, if so.
+            selected_items = [x for x in pg.action_list if x.is_selected]
+            action_names = [x.name for x in selected_items]
+            action_name_counts = Counter(action_names)
+            for action_name, count in action_name_counts.items():
+                if count > 1:
+                    layout.label(text=f'Duplicate action: {action_name}', icon='ERROR')
+                    break
+    
+        # Group
+        group_header, group_panel = sequences_panel.panel('Group', default_closed=True)
+        group_header.label(text='Group')
+        if group_panel is not None:
+            group_flow = group_panel.grid_flow()
+            group_flow.use_property_split = True
+            group_flow.use_property_decorate = False
+            group_flow.prop(pg, 'group_source')
+            if pg.group_source == 'CUSTOM':
+                group_flow.prop(pg, 'group_custom', placeholder='Group')
+
+        # Sampling
+        sampling_header, sampling_panel = sequences_panel.panel('Data Source', default_closed=False)
+        sampling_header.label(text='Sampling')
+        if sampling_panel:
+            flow = sampling_panel.grid_flow()
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+
+            # SAMPLING MODE
+            flow.prop(pg, 'sampling_mode', text='Sampling Mode')
+
+            # FPS
+            col = flow.row(align=True)
+            col.prop(pg, 'fps_source', text='FPS')
+            if pg.fps_source == 'CUSTOM':
+                col.prop(pg, 'fps_custom', text='')
+
+            # COMPRESSION RATIO
+            col = flow.row(align=True)
+            col.prop(pg, 'compression_ratio_source', text='Compression Ratio')
+            if pg.compression_ratio_source == 'CUSTOM':
+                col.prop(pg, 'compression_ratio_custom', text='')
+
+
+def create_psa_export_options(context: Context, armature_objects: Sequence[Object], pg: PsaExportMixin) -> PsaBuildOptions:
+    if len(armature_objects) == 0:
+        raise RuntimeError(f'No armatures')
+
+    animation_data = armature_objects[0].animation_data
+    export_sequences: list[PsaBuildSequence] = []
+
+    # TODO: this needs to be changed so that we iterate over all of the armature objects?
+    # do we need to check for primary key? (data vs. object?)
+
+    def get_export_sequence_group(group_source: str, group_custom: str | None, action: Action | None) -> str | None:
+        match group_source:
+            case 'ACTIONS':
+                if action is None:
+                    return None
+                action_psa_export = typing_cast(PSX_PG_action_export, getattr(action, 'psa_export'))
+                return action_psa_export.group
+            case 'CUSTOM':
+                return group_custom
+            case _:
+                return None
+
+    match pg.sequence_source:
+        case 'ACTIONS':
+            for action_item in filter(lambda x: x.is_selected, pg.action_list):
+                if action_item.action is None:
+                    continue
+                if len(action_item.action.layers) == 0:
+                    continue
+                export_sequence = PsaBuildSequence(context.active_object, animation_data)
+                export_sequence.name = action_item.name
+                export_sequence.group = get_export_sequence_group(pg.group_source, pg.group_custom, action_item.action)
+                export_sequence.nla_state.action = action_item.action
+                export_sequence.nla_state.frame_start = action_item.frame_start
+                export_sequence.nla_state.frame_end = action_item.frame_end
+                export_sequence.fps = get_sequence_fps(context, pg.fps_source, pg.fps_custom, [action_item.action])
+                export_sequence.compression_ratio = get_sequence_compression_ratio(pg.compression_ratio_source, pg.compression_ratio_custom, [action_item.action])
+                export_sequence.key_quota = action_item.action.psa_export.key_quota
+                export_sequences.append(export_sequence)
+        case 'TIMELINE_MARKERS':
+            for marker_item in filter(lambda x: x.is_selected, pg.marker_list):
+                nla_strips_actions: list[Action] = []
+                for nla_strip in get_nla_strips_in_frame_range(animation_data, marker_item.frame_start, marker_item.frame_end):
+                    if nla_strip.action:
+                        nla_strips_actions.append(nla_strip.action)
+                export_sequence = PsaBuildSequence(context.active_object, animation_data)
+                export_sequence.name = marker_item.name
+                export_sequence.group = get_export_sequence_group(pg.group_source, pg.group_custom, next(iter(nla_strips_actions), None))
+                export_sequence.nla_state.frame_start = marker_item.frame_start
+                export_sequence.nla_state.frame_end = marker_item.frame_end
+                export_sequence.fps = get_sequence_fps(context, pg.fps_source, pg.fps_custom, nla_strips_actions)
+                export_sequence.compression_ratio = get_sequence_compression_ratio(pg.compression_ratio_source, pg.compression_ratio_custom, nla_strips_actions)
+                export_sequences.append(export_sequence)
+        case 'NLA_TRACK_STRIPS':
+            for nla_strip_item in filter(lambda x: x.is_selected, pg.nla_strip_list):
+                if nla_strip_item.action is None:
+                    continue
+                export_sequence = PsaBuildSequence(context.active_object, animation_data)
+                export_sequence.name = nla_strip_item.name
+                export_sequence.group = get_export_sequence_group(pg.group_source, pg.group_custom, nla_strip_item.action)
+                export_sequence.nla_state.frame_start = nla_strip_item.frame_start
+                export_sequence.nla_state.frame_end = nla_strip_item.frame_end
+                export_sequence.fps = get_sequence_fps(context, pg.fps_source, pg.fps_custom, [nla_strip_item.action])
+                export_sequence.compression_ratio = get_sequence_compression_ratio(pg.compression_ratio_source, pg.compression_ratio_custom, [nla_strip_item.action])
+                export_sequence.key_quota = nla_strip_item.action.psa_export.key_quota
+                export_sequences.append(export_sequence)
+        case 'ACTIVE_ACTION':
+            for active_action_item in filter(lambda x: x.is_selected, pg.active_action_list):
+                export_sequence = PsaBuildSequence(active_action_item.armature_object, active_action_item.armature_object.animation_data)
+                action = active_action_item.action
+                if action is None:
+                    continue
+                export_sequence.name = action.name
+                export_sequence.group = get_export_sequence_group(pg.group_source, pg.group_custom, action)
+                export_sequence.nla_state.action = action
+                export_sequence.nla_state.frame_start = int(action.frame_range[0])
+                export_sequence.nla_state.frame_end = int(action.frame_range[1])
+                export_sequence.fps = get_sequence_fps(context, pg.fps_source, pg.fps_custom, [action])
+                export_sequence.compression_ratio = get_sequence_compression_ratio(pg.compression_ratio_source, pg.compression_ratio_custom, [action])
+                export_sequence.key_quota = action.psa_export.key_quota
+                export_sequences.append(export_sequence)
+        case _:
+            assert False, f'Invalid sequence source: {pg.sequence_source}'
+
+    options = PsaBuildOptions()
+    options.armature_objects = list(armature_objects)
+    options.animation_data = animation_data
+    options.sequences = export_sequences
+    options.bone_filter_mode = pg.bone_filter_mode
+    options.bone_collection_indices = [PsxBoneCollection(x.armature_object_name, x.armature_data_name, x.index) for x in pg.bone_collection_list if x.is_selected]
+    options.sequence_name_prefix = pg.sequence_name_prefix
+    options.sequence_name_suffix = pg.sequence_name_suffix
+    options.sampling_mode = pg.sampling_mode
+    options.export_space = pg.export_space
+    options.scale = pg.scale
+    options.forward_axis = pg.forward_axis
+    options.up_axis = pg.up_axis
+    options.sequence_source = pg.sequence_source
+
+    return options
+
+
+class PSA_OT_export(Operator, ExportHelper):
+    bl_idname = 'psa.export'
+    bl_label = 'Export'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Export actions to PSA'
+    filename_ext = '.psa'
+    filter_glob: StringProperty(default='*.psa', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for exporting the PSA file',
+        maxlen=1024,
+        default='')
+
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+        self.armature_objects: list[Object] = []
+
+    @classmethod
+    def poll(cls, context):
+        try:
+            cls._check_context(context)
+        except RuntimeError as e:
+            cls.poll_message_set(str(e))
+            return False
+        return True
+
+    def draw(self, context):
+        layout = self.layout
+        assert layout
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+
+        # SEQUENCES
+        draw_sequences_panel(layout, pg,
+                             PSA_OT_export_sequences_select_all.bl_idname, 
+                             PSA_OT_export_sequences_deselect_all.bl_idname)
+
+        # BONES
+        bones_header, bones_panel = layout.panel('Bones', default_closed=False)
+        bones_header.label(text='Bones', icon='BONE_DATA')
+        if bones_panel:
+            row = bones_panel.row(align=True)
+
+            draw_bone_filter_mode(row, pg)
+
+            if pg.bone_filter_mode == 'BONE_COLLECTIONS':
+                row = bones_panel.row(align=True)
+                row.label(text='Select')
+                row.operator(PSA_OT_export_bone_collections_select_all.bl_idname, text='All', icon='CHECKBOX_HLT')
+                row.operator(PSA_OT_export_bone_collections_deselect_all.bl_idname, text='None', icon='CHECKBOX_DEHLT')
+                rows = max(3, min(len(pg.bone_collection_list), 10))
+                bones_panel.template_list(
+                    'PSX_UL_bone_collection_list', '', pg, 'bone_collection_list', pg, 'bone_collection_list_index',
+                    rows=rows
+                    )
+
+        # TRANSFORM
+        transform_header, transform_panel = layout.panel('Advanced', default_closed=False)
+        transform_header.label(text='Transform', icon='DRIVER_TRANSFORM')
+
+        if transform_panel:
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'export_space')
+            flow.prop(pg, 'scale')
+            flow.prop(pg, 'forward_axis')
+            flow.prop(pg, 'up_axis')
+
+    @classmethod
+    def _check_context(cls, context):
+        if context.view_layer.objects.active is None:
+            raise RuntimeError('An armature must be selected')
+
+        if context.view_layer.objects.active.type != 'ARMATURE':
+            raise RuntimeError('The active object must be an armature')
+
+        if context.scene.is_nla_tweakmode:
+            raise RuntimeError('Cannot export PSA while in NLA tweak mode')
+
+    def invoke(self, context, event):
+        try:
+            self._check_context(context)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        pg: PSA_PG_export = getattr(context.scene, 'psa_export')
+
+        assert context.view_layer is not None
+
+        self.armature_objects = [x for x in context.view_layer.objects.selected if x.type == 'ARMATURE']
+
+        for armature_object in self.armature_objects:
+            # This is required otherwise the action list will be empty if the armature has never had its animation
+            # data created before (i.e. if no action was ever assigned to it).
+            if armature_object.animation_data is None:
+                armature_object.animation_data_create()
+
+
+        pg = getattr(context.scene, 'psa_export')
+        update_actions_and_timeline_markers(context, self.armature_objects, pg)
+        populate_bone_collection_list(
+            pg.bone_collection_list,
+            self.armature_objects,
+            primary_key='DATA' if pg.sequence_source == 'ACTIVE_ACTION' else 'OBJECT',
+            )
+
+        if context.window_manager is not None:
+            context.window_manager.fileselect_add(self)
+
+        return {'RUNNING_MODAL'}
+
+    def execute(self, context):
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+        options = create_psa_export_options(context, self.armature_objects, pg)
+
+        if len(options.sequences) == 0:
+            self.report({'ERROR'}, 'No sequences were selected for export')
+            return {'CANCELLED'}
+
+        try:
+            psa = build_psa(context, options)
+            self.report({'INFO'}, f'PSA export successful')
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        write_psa_to_file(psa, self.filepath)
+
+        return {'FINISHED'}
+
+
+class PsaExportActionsSelectOperator(Operator):
+    @classmethod
+    @abstractmethod
+    def get_psa_export(cls, context: Context) -> PsaExportMixin:
+        pass
+
+    @classmethod
+    def get_item_list(cls, context: Context):
+        pg = cls.get_psa_export(context)
+        match pg.sequence_source:
+            case 'ACTIONS':
+                return pg.action_list
+            case 'TIMELINE_MARKERS':
+                return pg.marker_list
+            case 'NLA_TRACK_STRIPS':
+                return pg.nla_strip_list
+            case 'ACTIVE_ACTION':
+                return pg.active_action_list
+            case _:
+                assert False, f'Invalid sequence source: {pg.sequence_source}'
+
+class PsaExportActionsSelectAllOperator(PsaExportActionsSelectOperator):
+    def execute(self, context):
+        pg = self.__class__.get_psa_export(context)
+        sequences = self.get_item_list(context)
+        for sequence in get_visible_sequences(pg, sequences):
+            sequence.is_selected = True
+        return {'FINISHED'}
+
+
+class PSA_OT_export_sequences_select_all(PsaExportActionsSelectAllOperator):
+    bl_idname = 'psa.export_actions_select_all'
+    bl_label = 'Select All'
+    bl_description = 'Select all visible sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def get_psa_export(cls, context: Context) -> PsaExportMixin:
+        return typing_cast(PsaExportMixin, getattr(context.scene, 'psa_export'))
+
+
+class PSA_OT_export_collection_sequences_select_all(PsaExportActionsSelectAllOperator):
+    bl_idname = 'psa.export_collection_sequences_select_all'
+    bl_label = 'Select All'
+    bl_description = 'Select all visible sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def get_psa_export(cls, context: Context) -> PsaExportMixin:
+        operator = get_collection_export_operator_from_context(context)
+        operator = typing_cast(PsaExportMixin, operator)
+        return operator
+
+
+class PsaExportActionsDeselectAllOperator(PsaExportActionsSelectOperator):
+    def execute(self, context):
+        pg = getattr(context.scene, 'psa_export')
+        item_list = self.get_item_list(context)
+        for sequence in get_visible_sequences(pg, item_list):
+            sequence.is_selected = False
+        return {'FINISHED'}
+
+
+class PSA_OT_export_collection_sequences_deselect_all(PsaExportActionsDeselectAllOperator):
+    bl_idname = 'psa.export_collection_sequences_deselect_all'
+    bl_label = 'Deselect All'
+    bl_description = 'Deselect all visible sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def get_psa_export(cls, context: Context) -> PsaExportMixin:
+        operator = get_collection_export_operator_from_context(context)
+        operator = typing_cast(PsaExportMixin, operator)
+        return operator
+
+
+class PSA_OT_export_sequences_deselect_all(PsaExportActionsDeselectAllOperator):
+    bl_idname = 'psa.export_sequences_deselect_all'
+    bl_label = 'Deselect All'
+    bl_description = 'Deselect all visible sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def get_psa_export(cls, context: Context) -> PsaExportMixin:
+        return typing_cast(PsaExportMixin, getattr(context.scene, 'psa_export'))
+
+
+class PSA_OT_export_bone_collections_select_all(Operator):
+    bl_idname = 'psa.export_bone_collections_select_all'
+    bl_label = 'Select All'
+    bl_description = 'Select all bone collections'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def poll(cls, context):
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+        item_list = pg.bone_collection_list
+        has_unselected_items = any(map(lambda action: not action.is_selected, item_list))
+        return len(item_list) > 0 and has_unselected_items
+
+    def execute(self, context):
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+        for item in pg.bone_collection_list:
+            item.is_selected = True
+        return {'FINISHED'}
+
+
+class PSA_OT_export_bone_collections_deselect_all(Operator):
+    bl_idname = 'psa.export_bone_collections_deselect_all'
+    bl_label = 'Deselect All'
+    bl_description = 'Deselect all bone collections'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def poll(cls, context):
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+        item_list = pg.bone_collection_list
+        has_selected_actions = any(map(lambda action: action.is_selected, item_list))
+        return len(item_list) > 0 and has_selected_actions
+
+    def execute(self, context):
+        pg = typing_cast(PSA_PG_export, getattr(context.scene, 'psa_export'))
+        for action in pg.bone_collection_list:
+            action.is_selected = False
+        return {'FINISHED'}
+
+
+class PSA_OT_export_collection_populate_sequences(Operator):
+    bl_idname = 'psa.export_collection_populate_sequences'
+    bl_label = 'Populate Sequences'
+    bl_description = 'Populate the sequences list based on the armatures in the collection'
+    bl_options = {'INTERNAL'}
+
+    def execute(self, context: Context):
+        export_operator = get_collection_export_operator_from_context(context)
+        assert export_operator is not None
+        export_operator = typing_cast(PSA_OT_export_collection, export_operator)
+        collection = get_collection_from_context(context)
+        if collection is None:
+            self.report({'ERROR'}, 'No collection found in context')
+            return {'CANCELLED'}
+        
+        try:
+            input_objects = get_psk_input_objects_for_collection(collection)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        # Keep track of what sequences were selected, then restore the selected status after we have updated the lists.
+        def store_is_selected_for_sequence_list(sequences: Iterable[PsaExportSequenceMixin]) -> dict[int, bool]:
+            return {hash(x): x.is_selected for x in sequences}
+    
+        def restore_is_selected_for_sequence_list(sequence_list: Iterable[PsaExportSequenceMixin], is_selected_map: dict[int, bool]):
+            for sequence in sequence_list:
+                sequence.is_selected = is_selected_map.get(hash(sequence), False)
+
+        action_list_is_selected = store_is_selected_for_sequence_list(export_operator.action_list)
+        markers_list_is_selected = store_is_selected_for_sequence_list(export_operator.marker_list)
+        nla_strip_list_is_selected = store_is_selected_for_sequence_list(export_operator.nla_strip_list)
+        active_action_list_is_selected = store_is_selected_for_sequence_list(export_operator.active_action_list)
+
+        update_actions_and_timeline_markers(context, input_objects.armature_objects, export_operator)
+
+        restore_is_selected_for_sequence_list(export_operator.action_list, action_list_is_selected)
+        restore_is_selected_for_sequence_list(export_operator.marker_list, markers_list_is_selected)
+        restore_is_selected_for_sequence_list(export_operator.nla_strip_list, nla_strip_list_is_selected)
+        restore_is_selected_for_sequence_list(export_operator.active_action_list, active_action_list_is_selected)
+        
+        return {'FINISHED'}
+
+
+_classes = (
+    PSA_OT_export,
+    PSA_OT_export_collection,
+    PSA_OT_export_sequences_select_all,
+    PSA_OT_export_sequences_deselect_all,
+    PSA_OT_export_collection_sequences_select_all,
+    PSA_OT_export_collection_sequences_deselect_all,
+    PSA_OT_export_bone_collections_select_all,
+    PSA_OT_export_bone_collections_deselect_all,
+    PSA_OT_export_collection_populate_sequences,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/psa/export/properties.py

@@ -0,0 +1,302 @@
+import re
+import sys
+from fnmatch import fnmatch
+from typing import Sequence
+import bpy
+from bpy.props import (
+    BoolProperty,
+    EnumProperty,
+    FloatProperty,
+    CollectionProperty,
+    IntProperty,
+    StringProperty,
+)
+from bpy.types import PropertyGroup, Object, Action, AnimData, Context
+
+from ...shared.dfs import dfs_view_layer_objects
+from ...shared.helpers import populate_bone_collection_list
+from ...shared.types import TransformMixin, ExportSpaceMixin, PsxBoneExportMixin, TransformSourceMixin
+
+
+def psa_export_property_group_animation_data_override_poll(_context, obj):
+    return obj.animation_data is not None
+
+
+class PsaExportSequenceMixin(PropertyGroup):
+    name: StringProperty(name='Name')
+    is_selected: BoolProperty(name='Selected', default=True)
+    frame_start: IntProperty(name='Start Frame', options={'HIDDEN'})
+    frame_end: IntProperty(name='End Frame', options={'HIDDEN'})
+    group: StringProperty(name='Group')
+    action_name: StringProperty(name='Action Name',default='', options={'HIDDEN'})
+    armature_object_name: StringProperty(name='Armature Object Name',default='', options={'HIDDEN'})
+    marker_index: IntProperty(name='Marker Index',default=-1, options={'HIDDEN'})
+    is_pose_marker: BoolProperty(name='Is Pose Marker',default=False, options={'HIDDEN'})
+
+    @property
+    def action(self) -> Action | None:
+        """Get the action associated with this sequence (if any)."""
+        return bpy.data.actions.get(self.action_name) if self.action_name else None
+
+    @property
+    def armature_object(self) -> Object | None:
+        """Get the armature object associated with this sequence (if any)."""
+        return bpy.data.objects.get(self.armature_object_name) if self.armature_object_name else None
+    
+    @property
+    def is_reversed(self) -> bool:
+        """Check if the sequence is reversed (end frame before start frame)."""
+        return self.frame_end < self.frame_start
+
+    def __hash__(self) -> int:
+        return hash(self.name)
+
+
+class PSA_PG_export_sequence(PsaExportSequenceMixin):
+    pass
+
+
+def get_sequences_from_name_and_frame_range(name: str, frame_start: int, frame_end: int):
+    # Check for loop
+    anims: list[tuple[str, int, int]] = []
+    loop_pattern = r'\@(\d+)\:(.+)'
+    loop_match = re.match(loop_pattern, name)
+    if loop_match:
+        frame_count = max(1, int(loop_match.group(1)))
+        sequence_name = loop_match.group(2)
+        iteration = 0
+        frame = frame_start
+        while frame + frame_count <= frame_end:
+            output_name = sequence_name.format(index=iteration)
+            iteration_frame_start = frame
+            iteration_frame_end = frame + frame_count - 1
+            anims.append((output_name, iteration_frame_start, iteration_frame_end))
+            frame += frame_count
+            iteration += 1
+    else:
+        # If not, just treat it as a single animation, but parse for the reverse pattern as well.
+        anims.append((name, frame_start, frame_end))
+
+    for (name, frame_start, frame_end) in anims:
+        reversed_pattern = r'(.+)/(.+)'
+        reversed_match = re.match(reversed_pattern, name)
+        if reversed_match:
+            forward_name = reversed_match.group(1)
+            backwards_name = reversed_match.group(2)
+            yield forward_name, frame_start, frame_end
+            yield backwards_name, frame_end, frame_start
+        else:
+            yield name, frame_start, frame_end
+
+
+def nla_track_update_cb(self: 'PSA_PG_export', context: Context) -> None:
+    self.nla_strip_list.clear()
+    match = re.match(r'^(\d+).+$', self.nla_track)
+    self.nla_track_index = int(match.group(1)) if match else -1
+    if self.nla_track_index >= 0:
+        animation_data = get_animation_data(self, context)
+        if animation_data is None:
+            return
+        nla_track = animation_data.nla_tracks[self.nla_track_index]
+        for nla_strip in nla_track.strips:
+            for sequence_name, frame_start, frame_end in get_sequences_from_name_and_frame_range(nla_strip.name, nla_strip.frame_start, nla_strip.frame_end):
+                strip: PSA_PG_export_sequence = self.nla_strip_list.add()
+                strip.action_name = nla_strip.action
+                strip.name = sequence_name
+                strip.frame_start = frame_start
+                strip.frame_end = frame_end
+
+
+def get_animation_data(pg: 'PSA_PG_export', context: Context) -> AnimData | None:
+    animation_data_object = context.object
+    return animation_data_object.animation_data if animation_data_object else None
+
+
+def nla_track_search_cb(self, context: Context, edit_text: str):
+    pg = getattr(context.scene, 'psa_export')
+    animation_data = get_animation_data(pg, context)
+    if animation_data is not None:
+        for index, nla_track in enumerate(animation_data.nla_tracks):
+            yield f'{index} - {nla_track.name}'
+
+
+def animation_data_override_update_cb(self: 'PSA_PG_export', context: Context):
+    # Reset NLA track selection
+    self.nla_track = ''
+
+
+sequence_source_items = (
+    ('ACTIONS', 'Actions', 'Sequences will be exported using actions', 'ACTION', 0),
+    ('TIMELINE_MARKERS', 'Timeline Markers', 'Sequences are delineated by scene timeline markers', 'MARKER_HLT', 1),
+    ('NLA_TRACK_STRIPS', 'NLA Track Strips', 'Sequences are delineated by the start & end times of strips on the selected NLA track', 'NLA', 2),
+    ('ACTIVE_ACTION', 'Active Action', 'The active action will be exported for each selected armature', 'ACTION', 3),
+)
+
+fps_source_items = (
+    ('SCENE', 'Scene', '', 'SCENE_DATA', 0),
+    ('ACTION_METADATA', 'Action Metadata', 'The frame rate will be determined by action\'s FPS property found in the PSA Export panel.\n\nIf the Sequence Source is Timeline Markers, the lowest value of all contributing actions will be used', 'ACTION', 1),
+    ('CUSTOM', 'Custom', '', 2)
+)
+
+compression_ratio_source_items = (
+    ('ACTION_METADATA', 'Action Metadata', 'The compression ratio will be determined by action\'s Compression Ratio property found in the PSA Export panel.\n\nIf the Sequence Source is Timeline Markers, the lowest value of all contributing actions will be used', 'ACTION', 1),
+    ('CUSTOM', 'Custom', '', 2)
+)
+
+sampling_mode_items = (
+    ('INTERPOLATED', 'Interpolated', 'Sampling is performed by interpolating the evaluated bone poses from the adjacent whole frames.', 'INTERPOLATED', 0),
+    ('SUBFRAME', 'Subframe', 'Sampling is performed by evaluating the bone poses at the subframe time.\n\nNot recommended unless you are also animating with subframes enabled.', 'SUBFRAME', 1),
+)
+
+group_source_items = (
+    ('ACTIONS', 'Actions', '', 0),
+    ('CUSTOM', 'Custom', '', 1),
+)
+
+
+def sequence_source_update_cb(self: 'PSA_PG_export', context: Context) -> None:
+    armature_objects = []
+    assert context.view_layer
+    for dfs_object in dfs_view_layer_objects(context.view_layer):
+        if dfs_object.obj.type == 'ARMATURE' and dfs_object.is_selected:
+            armature_objects.append(dfs_object.obj)
+
+    populate_bone_collection_list(
+        self.bone_collection_list,
+        armature_objects,
+        primary_key='DATA' if self.sequence_source == 'ACTIVE_ACTION' else 'OBJECT')
+
+
+class PsaExportMixin(PropertyGroup, TransformMixin, ExportSpaceMixin, PsxBoneExportMixin, TransformSourceMixin):
+    sequence_source: EnumProperty(
+        name='Source',
+        options=set(),
+        description='',
+        items=sequence_source_items,
+        update=sequence_source_update_cb,
+    )
+    nla_track: StringProperty(
+        name='NLA Track',
+        options=set(),
+        description='',
+        search=nla_track_search_cb,
+        update=nla_track_update_cb
+    )
+    nla_track_index: IntProperty(name='NLA Track Index', default=-1)
+    fps_source: EnumProperty(
+        name='FPS Source',
+        options=set(),
+        description='',
+        items=fps_source_items,
+    )
+    fps_custom: FloatProperty(default=30.0, min=sys.float_info.epsilon, soft_min=1.0, options=set(), step=100, soft_max=60.0)
+    compression_ratio_source: EnumProperty(
+        name='Compression Ratio Source',
+        options=set(),
+        description='',
+        items=compression_ratio_source_items,
+    )
+    compression_ratio_custom: FloatProperty(default=1.0, min=0.0, max=1.0, subtype='FACTOR', description='The key sampling ratio of the exported sequence.\n\nA compression ratio of 1.0 will export all frames, while a compression ratio of 0.5 will export half of the frames')
+
+    action_list: CollectionProperty(type=PSA_PG_export_sequence)
+    action_list_index: IntProperty(default=0)
+    marker_list: CollectionProperty(type=PSA_PG_export_sequence)
+    marker_list_index: IntProperty(default=0)
+    nla_strip_list: CollectionProperty(type=PSA_PG_export_sequence)
+    nla_strip_list_index: IntProperty(default=0)
+    active_action_list: CollectionProperty(type=PSA_PG_export_sequence)
+    active_action_list_index: IntProperty(default=0)
+
+    sequence_name_prefix: StringProperty(name='Prefix', options=set())
+    sequence_name_suffix: StringProperty(name='Suffix', options=set())
+    sequence_filter_name: StringProperty(
+        default='',
+        name='Filter by Name',
+        options={'TEXTEDIT_UPDATE'},
+        description='Only show items matching this name (use \'*\' as wildcard)')
+    sequence_use_filter_invert: BoolProperty(
+        default=False,
+        name='Invert',
+        options=set(),
+        description='Invert filtering (show hidden items, and vice versa)')
+    sequence_filter_asset: BoolProperty(
+        default=False,
+        name='Show assets',
+        options=set(),
+        description='Show actions that belong to an asset library')
+    sequence_filter_pose_marker: BoolProperty(
+        default=True,
+        name='Show pose markers',
+        options=set())
+    sequence_use_filter_sort_reverse: BoolProperty(default=True, options=set())
+    sequence_filter_reversed: BoolProperty(
+        default=True,
+        options=set(),
+        name='Show Reversed',
+        description='Show reversed sequences'
+    )
+    sampling_mode: EnumProperty(
+        name='Sampling Mode',
+        options=set(),
+        description='The method by which frames are sampled',
+        items=sampling_mode_items,
+        default='INTERPOLATED'
+    )
+    group_source: EnumProperty(
+        name='Group Source',
+        options=set(),
+        description='The source of the exported sequence\'s group property',
+        items=group_source_items,
+        default='ACTIONS'
+    )
+    group_custom: StringProperty(
+        name='Group',
+        options=set(),
+        description='The group to apply to all exported sequences. Only applicable when Group Source is Custom.'
+    )
+
+class PSA_PG_export(PsaExportMixin):
+    pass
+
+
+def filter_sequences(pg: PsaExportMixin, sequences: Sequence[PsaExportSequenceMixin]) -> list[int]:
+    bitflag_filter_item = 1 << 30
+    flt_flags = [bitflag_filter_item] * len(sequences)
+
+    if pg.sequence_filter_name:
+        # Filter name is non-empty.
+        for i, sequence in enumerate(sequences):
+            if not fnmatch(sequence.name, f'*{pg.sequence_filter_name}*'):
+                flt_flags[i] &= ~bitflag_filter_item
+
+        # Invert filter flags for all items.
+        if pg.sequence_use_filter_invert:
+            for i, sequence in enumerate(sequences):
+                flt_flags[i] ^= bitflag_filter_item
+
+    if not pg.sequence_filter_asset:
+        for i, sequence in enumerate(sequences):
+            if sequence.action is not None and sequence.action.asset_data is not None:
+                flt_flags[i] &= ~bitflag_filter_item
+
+    if not pg.sequence_filter_pose_marker:
+        for i, sequence in enumerate(sequences):
+            if sequence.is_pose_marker:
+                flt_flags[i] &= ~bitflag_filter_item
+
+    if not pg.sequence_filter_reversed:
+        for i, sequence in enumerate(sequences):
+            if sequence.is_reversed:
+                flt_flags[i] &= ~bitflag_filter_item
+
+    return flt_flags
+
+
+_classes = (
+    PSA_PG_export_sequence,
+    PSA_PG_export,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/psa/export/properties.pyi

@@ -0,0 +1,68 @@
+from bpy.types import PropertyGroup, Object, Action
+
+from ...shared.types import BpyCollectionProperty, TransformMixin, ExportSpaceMixin, PsxBoneExportMixin, TransformSourceMixin
+
+class PsaExportSequenceMixin(PropertyGroup):
+    name: str
+    is_selected: bool
+    frame_start: int
+    frame_end: int
+    group: str
+    action_name: str
+    armature_object_name: str
+    marker_index: int
+    is_pose_marker: bool
+
+    @property
+    def action(self) -> Action | None: ...
+
+    @property
+    def armature_object(self) -> Object | None: ...
+
+    @property
+    def is_reversed(self) -> bool: ...
+
+
+class PSA_PG_export_sequence(PsaExportSequenceMixin):
+    """Concrete type for PSA export sequences."""
+    pass
+
+
+class PsaExportMixin(PropertyGroup, TransformMixin, ExportSpaceMixin, PsxBoneExportMixin, TransformSourceMixin):
+    sequence_source: str
+    nla_track: str
+    nla_track_index: int
+    fps_source: str
+    fps_custom: float
+    compression_ratio_source: str
+    compression_ratio_custom: float
+    action_list: BpyCollectionProperty[PSA_PG_export_sequence]
+    action_list_index: int
+    marker_list: BpyCollectionProperty[PSA_PG_export_sequence]
+    marker_list_index: int
+    nla_strip_list: BpyCollectionProperty[PSA_PG_export_sequence]
+    nla_strip_list_index: int
+    active_action_list: BpyCollectionProperty[PSA_PG_export_sequence]
+    active_action_list_index: int
+    sequence_name_prefix: str
+    sequence_name_suffix: str
+    sequence_filter_name: str
+    sequence_use_filter_invert: bool
+    sequence_filter_asset: bool
+    sequence_filter_pose_marker: bool
+    sequence_use_filter_sort_reverse: bool
+    sequence_filter_reversed: bool
+    sampling_mode: str
+    group_source: str
+    group_custom: str
+
+
+class PSA_PG_export(PsaExportMixin):
+    pass
+
+
+def get_sequences_from_name_and_frame_range(name: str, frame_start: int, frame_end: int):
+    pass
+
+def filter_sequences(pg: PsaExportMixin, sequences) -> list[int]:
+    pass

io_scene_psk_psa/psa/export/ui.py

@@ -0,0 +1,61 @@
+from typing import cast as typing_cast
+
+from bpy.types import UIList
+
+from .properties import PsaExportSequenceMixin, filter_sequences
+
+
+class PSA_UL_export_sequences(UIList):
+    bl_idname = 'PSA_UL_export_sequences'
+
+    def __init__(self, *args, **kwargs):
+        super(PSA_UL_export_sequences, self).__init__(*args, **kwargs)
+        # Show the filtering options by default.
+        self.use_filter_show = True
+
+    def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index):
+        item = typing_cast(PsaExportSequenceMixin, item)
+
+        is_pose_marker = hasattr(item, 'is_pose_marker') and item.is_pose_marker
+        layout.prop(item, 'is_selected', icon_only=True, text=item.name)
+        if hasattr(item, 'action') and item.action is not None and item.action.asset_data is not None:
+            layout.label(text='', icon='ASSET_MANAGER')
+
+        row = layout.row(align=True)
+        row.alignment = 'RIGHT'
+
+        row.label(text=str(abs(item.frame_end - item.frame_start) + 1), icon='FRAME_PREV' if item.is_reversed else 'KEYFRAME')
+
+        if item.armature_object is not None:
+            row.label(text=item.armature_object.name, icon='ARMATURE_DATA')
+
+        # row.label(text=item.action.name, icon='PMARKER' if is_pose_marker else 'ACTION_DATA')
+
+    def draw_filter(self, context, layout):
+        pg = getattr(context.scene, 'psa_export')
+        row = layout.row()
+        subrow = row.row(align=True)
+        subrow.prop(pg, 'sequence_filter_name', text='')
+        subrow.prop(pg, 'sequence_use_filter_invert', text='', icon='ARROW_LEFTRIGHT')
+
+        if pg.sequence_source == 'ACTIONS':
+            subrow = row.row(align=True)
+            subrow.prop(pg, 'sequence_filter_asset', icon_only=True, icon='ASSET_MANAGER')
+            subrow.prop(pg, 'sequence_filter_pose_marker', icon_only=True, icon='PMARKER')
+            subrow.prop(pg, 'sequence_filter_reversed', text='', icon='FRAME_PREV')
+
+    def filter_items(self, context, data, prop):
+        pg = getattr(context.scene, 'psa_export')
+        actions = getattr(data, prop)
+        flt_flags = filter_sequences(pg, actions)
+        flt_neworder = list(range(len(actions)))
+        return flt_flags, flt_neworder
+
+
+_classes = (
+    PSA_UL_export_sequences,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/psa/file_handlers.py

@@ -0,0 +1,24 @@
+from bpy.types import Context
+from bpy.types import FileHandler
+
+from .import_.operators import PSA_OT_import_drag_and_drop
+from .export.operators import PSA_OT_export_collection
+
+class PSA_FH_file_handler(FileHandler):
+    bl_idname = 'PSA_FH_file_handler'
+    bl_label = 'Unreal PSA'
+    bl_import_operator = PSA_OT_import_drag_and_drop.bl_idname
+    bl_export_operator = PSA_OT_export_collection.bl_idname
+    bl_file_extensions = '.psa'
+
+    @classmethod
+    def poll_drop(cls, context: Context) -> bool:
+        return context.area is not None and context.area.type == 'VIEW_3D'
+
+
+_classes = (
+    PSA_FH_file_handler,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psa/import_/operators.py

@@ -0,0 +1,468 @@
+import os
+from pathlib import Path
+from typing import Iterable
+
+from bpy.props import CollectionProperty, StringProperty
+from bpy.types import Context, Event, Object, Operator, OperatorFileListElement
+from bpy_extras.io_utils import ImportHelper
+
+from .properties import PsaImportMixin, get_visible_sequences
+from ..config import read_psa_config
+from ..importer import BoneMapping, PsaImportOptions, import_psa
+from psk_psa_py.psa.reader import PsaReader
+
+
+def psa_import_poll(cls, context: Context):
+    if context.view_layer is None or context.view_layer.objects.active is None:
+        return False
+    active_object = context.view_layer.objects.active
+    if active_object is None or active_object.type != 'ARMATURE':
+        cls.poll_message_set('The active object must be an armature')
+        return False
+    return True
+
+
+class PSA_OT_import_sequences_select_from_text(Operator):
+    bl_idname = 'psa.import_sequences_select_from_text'
+    bl_label = 'Select By Text List'
+    bl_description = 'Select sequences by name from text list'
+    bl_options = {'INTERNAL', 'UNDO'}
+
+    @classmethod
+    def poll(cls, context):
+        pg = getattr(context.scene, 'psa_import')
+        return len(pg.sequence_list) > 0
+
+    def invoke(self, context, event):
+        assert context.window_manager
+        return context.window_manager.invoke_props_dialog(self, width=256)
+
+    def draw(self, context):
+        layout = self.layout
+        assert layout
+        pg = getattr(context.scene, 'psa_import')
+        layout.label(icon='INFO', text='Each sequence name should be on a new line.')
+        layout.prop(pg, 'select_text', text='')
+
+    def execute(self, context):
+        pg = getattr(context.scene, 'psa_import')
+        if pg.select_text is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No text block selected')
+            return {'CANCELLED'}
+        contents = pg.select_text.as_string()
+        count = 0
+        for line in contents.split('\n'):
+            for sequence in pg.sequence_list:
+                if sequence.action_name == line:
+                    sequence.is_selected = True
+                    count += 1
+        self.report({'INFO'}, f'Selected {count} sequence(s)')
+        return {'FINISHED'}
+
+
+class PSA_OT_import_sequences_select_all(Operator):
+    bl_idname = 'psa.import_sequences_select_all'
+    bl_label = 'All'
+    bl_description = 'Select all sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def poll(cls, context):
+        pg = getattr(context.scene, 'psa_import')
+        visible_sequences = get_visible_sequences(pg, pg.sequence_list)
+        has_unselected_actions = any(map(lambda action: not action.is_selected, visible_sequences))
+        return len(visible_sequences) > 0 and has_unselected_actions
+
+    def execute(self, context):
+        pg = getattr(context.scene, 'psa_import')
+        visible_sequences = get_visible_sequences(pg, pg.sequence_list)
+        for sequence in visible_sequences:
+            sequence.is_selected = True
+        return {'FINISHED'}
+
+
+class PSA_OT_import_sequences_deselect_all(Operator):
+    bl_idname = 'psa.import_sequences_deselect_all'
+    bl_label = 'None'
+    bl_description = 'Deselect all visible sequences'
+    bl_options = {'INTERNAL'}
+
+    @classmethod
+    def poll(cls, context):
+        pg = getattr(context.scene, 'psa_import')
+        visible_sequences = get_visible_sequences(pg, pg.sequence_list)
+        has_selected_sequences = any(map(lambda sequence: sequence.is_selected, visible_sequences))
+        return len(visible_sequences) > 0 and has_selected_sequences
+
+    def execute(self, context):
+        pg = getattr(context.scene, 'psa_import')
+        visible_sequences = get_visible_sequences(pg, pg.sequence_list)
+        for sequence in visible_sequences:
+            sequence.is_selected = False
+        return {'FINISHED'}
+
+
+def load_psa_file(context, filepath: str):
+    pg = context.scene.psa_import
+    pg.sequence_list.clear()
+    pg.psa.bones.clear()
+    pg.psa_error = ''
+    try:
+        # Read the file and populate the action list.
+        p = os.path.abspath(filepath)
+        psa_reader = PsaReader.from_path(p)
+        for sequence in psa_reader.sequences.values():
+            item = pg.sequence_list.add()
+            item.action_name = sequence.name.decode('windows-1252')
+        for psa_bone in psa_reader.bones:
+            item = pg.psa.bones.add()
+            item.bone_name = psa_bone.name.decode('windows-1252')
+    except Exception as e:
+        pg.psa_error = str(e)
+
+
+def on_psa_file_path_updated(cls, context):
+    load_psa_file(context, cls.filepath)
+
+
+class PSA_OT_import_drag_and_drop(Operator, PsaImportMixin):
+    bl_idname = 'psa.import_drag_and_drop'
+    bl_label = 'Import PSA'
+    bl_description = 'Import multiple PSA files'
+    bl_options = {'INTERNAL', 'UNDO', 'PRESET'}
+
+    directory: StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
+    files: CollectionProperty(type=OperatorFileListElement, options={'SKIP_SAVE', 'HIDDEN'})
+
+    def execute(self, context):
+        warnings = []
+        sequences_count = 0
+
+        assert context.view_layer and context.view_layer.objects.active
+
+        for file in self.files:
+            psa_path = str(os.path.join(self.directory, file.name))
+            psa_reader = PsaReader.from_path(psa_path)
+            sequence_names = list(psa_reader.sequences.keys())
+            options = psa_import_options_from_property_group(self, sequence_names)
+
+            sequences_count += len(sequence_names)
+
+            result = _import_psa(context, options, psa_path, context.view_layer.objects.active)
+            warnings.extend(result.warnings)
+
+        if len(warnings) > 0:
+            message = f'Imported {sequences_count} action(s) from {len(self.files)} file(s) with {len(warnings)} warning(s)\n'
+            self.report({'INFO'}, message)
+            for warning in warnings:
+                self.report({'WARNING'}, warning)
+
+        self.report({'INFO'}, f'Imported {sequences_count} action(s) from {len(self.files)} file(s)')
+
+        return {'FINISHED'}
+
+    def invoke(self, context: Context, event):
+        # Make sure the selected object is an obj.
+        assert context.view_layer and context.view_layer.objects.active
+        active_object = context.view_layer.objects.active
+        if active_object is None or active_object.type != 'ARMATURE':
+            self.report({'ERROR_INVALID_CONTEXT'}, 'The active object must be an armature')
+            return {'CANCELLED'}
+
+        # Show the import operator properties in a pop-up dialog (do not use the file selector).
+        assert context.window_manager
+        context.window_manager.invoke_props_dialog(self)
+        return {'RUNNING_MODAL'}
+
+    def draw(self, context):
+        layout = self.layout
+        draw_psa_import_options_no_panels(layout, self)
+
+
+def psa_import_options_from_property_group(pg: PsaImportMixin, sequence_names: Iterable[str]) -> PsaImportOptions:
+    options = PsaImportOptions()
+    options.sequence_names = list(sequence_names)
+    options.should_use_fake_user = pg.should_use_fake_user
+    options.should_stash = pg.should_stash
+    options.action_name_prefix = pg.action_name_prefix if pg.should_use_action_name_prefix else ''
+    options.should_overwrite = pg.should_overwrite
+    options.should_write_metadata = pg.should_write_metadata
+    options.should_write_keyframes = pg.should_write_keyframes
+    options.should_write_scale_keys = pg.should_write_scale_keys
+    options.should_convert_to_samples = pg.should_convert_to_samples
+    options.bone_mapping = BoneMapping(
+        is_case_sensitive=pg.bone_mapping_is_case_sensitive,
+        should_ignore_trailing_whitespace=pg.bone_mapping_should_ignore_trailing_whitespace
+    )
+    options.fps_source = pg.fps_source
+    options.fps_custom = pg.fps_custom
+    options.translation_scale = pg.translation_scale
+    return options
+
+
+def _import_psa(context,
+                options: PsaImportOptions,
+                filepath: str,
+                armature_object: Object
+                ):
+    warnings = []
+
+    if options.should_use_config_file:
+        # Read the PSA config file if it exists.
+        config_path = Path(filepath).with_suffix('.config')
+        if config_path.exists():
+            try:
+                options.psa_config = read_psa_config(options.sequence_names, str(config_path))
+            except Exception as e:
+                warnings.append(f'Failed to read PSA config file: {e}')
+
+    psa_reader = PsaReader.from_path(filepath)
+
+    result = import_psa(context, psa_reader, armature_object, options)
+    result.warnings.extend(warnings)
+
+    return result
+
+
+class PSA_OT_import_all(Operator, PsaImportMixin):
+    bl_idname = 'psa.import_all'
+    bl_label = 'Import PSA'
+    bl_description = 'Import all sequences from the selected PSA file'
+    bl_options = {'INTERNAL', 'UNDO'}
+
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for importing the PSA file',
+        maxlen=1024,
+        default='',
+        update=on_psa_file_path_updated)
+
+    @classmethod
+    def poll(cls, context):
+        return psa_import_poll(cls, context)
+
+    def execute(self, context):
+        sequence_names = []
+        with PsaReader.from_path(self.filepath) as psa_reader:
+            sequence_names.extend(psa_reader.sequences.keys())
+
+        options = PsaImportOptions(
+            action_name_prefix=self.action_name_prefix,
+            bone_mapping=BoneMapping(
+                is_case_sensitive=self.bone_mapping_is_case_sensitive,
+                should_ignore_trailing_whitespace=self.bone_mapping_should_ignore_trailing_whitespace
+            ),
+            fps_custom=self.fps_custom,
+            fps_source=self.fps_source,
+            sequence_names=sequence_names,
+            should_convert_to_samples=self.should_convert_to_samples,
+            should_overwrite=self.should_overwrite,
+            should_stash=self.should_stash,
+            should_use_config_file=self.should_use_config_file,
+            should_use_fake_user=self.should_use_fake_user,
+            should_write_keyframes=self.should_write_keyframes,
+            should_write_metadata=self.should_write_metadata,
+            translation_scale=self.translation_scale
+        )
+
+        assert context.view_layer
+        assert context.view_layer.objects.active
+        result = _import_psa(context, options, self.filepath, context.view_layer.objects.active)
+
+        if len(result.warnings) > 0:
+            message = f'Imported {len(options.sequence_names)} action(s) with {len(result.warnings)} warning(s)\n'
+            self.report({'WARNING'}, message)
+            for warning in result.warnings:
+                self.report({'WARNING'}, warning)
+        else:
+            self.report({'INFO'}, f'Imported {len(options.sequence_names)} action(s)')
+
+        return {'FINISHED'}
+
+    def draw(self, context: Context):
+        draw_psa_import_options_no_panels(self.layout, self)
+
+
+class PSA_OT_import(Operator, ImportHelper, PsaImportMixin):
+    bl_idname = 'psa.import_file'
+    bl_label = 'Import'
+    bl_description = 'Import the selected animations into the scene as actions'
+    bl_options = {'INTERNAL', 'UNDO'}
+
+    filename_ext = '.psa'
+    filter_glob: StringProperty(default='*.psa', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for importing the PSA file',
+        maxlen=1024,
+        default='',
+        update=on_psa_file_path_updated)
+
+    @classmethod
+    def poll(cls, context):
+        return psa_import_poll(cls, context)
+
+    def execute(self, context):
+        pg = getattr(context.scene, 'psa_import')
+        options = psa_import_options_from_property_group(self, [x.action_name for x in pg.sequence_list if x.is_selected])
+
+        if len(options.sequence_names) == 0:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No sequences selected')
+            return {'CANCELLED'}
+
+        result = _import_psa(context, options, self.filepath, context.view_layer.objects.active)
+
+        if len(result.warnings) > 0:
+            message = f'Imported {len(options.sequence_names)} action(s) with {len(result.warnings)} warning(s)\n'
+            self.report({'WARNING'}, message)
+            for warning in result.warnings:
+                self.report({'WARNING'}, warning)
+        else:
+            self.report({'INFO'}, f'Imported {len(options.sequence_names)} action(s)')
+
+        return {'FINISHED'}
+
+    def invoke(self, context: Context, event: Event):
+        # Attempt to load the PSA file for the pre-selected file.
+        load_psa_file(context, self.filepath)
+        assert context.window_manager
+        context.window_manager.fileselect_add(self)
+        return {'RUNNING_MODAL'}
+
+    def draw(self, context: Context):
+        layout = self.layout
+        assert layout
+        pg = getattr(context.scene, 'psa_import')
+
+        sequences_header, sequences_panel = layout.panel('sequences_panel_id', default_closed=False)
+        sequences_header.label(text='Sequences')
+
+        if sequences_panel:
+            if pg.psa_error:
+                row = sequences_panel.row()
+                row.label(text='Select a PSA file', icon='ERROR')
+            else:
+                # Select buttons.
+                rows = max(3, min(len(pg.sequence_list), 10))
+
+                row = sequences_panel.row()
+                col = row.column()
+
+                row2 = col.row(align=True)
+                row2.label(text='Select')
+                row2.operator(PSA_OT_import_sequences_select_from_text.bl_idname, text='', icon='TEXT')
+                row2.operator(PSA_OT_import_sequences_select_all.bl_idname, text='All', icon='CHECKBOX_HLT')
+                row2.operator(PSA_OT_import_sequences_deselect_all.bl_idname, text='None', icon='CHECKBOX_DEHLT')
+
+                col = col.row()
+                col.template_list('PSA_UL_import_sequences', '', pg, 'sequence_list', pg, 'sequence_list_index', rows=rows)
+
+            col = sequences_panel.column(heading='')
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(self, 'fps_source')
+            if self.fps_source == 'CUSTOM':
+                col.prop(self, 'fps_custom')
+            col.prop(self, 'should_overwrite')
+            col.prop(self, 'should_use_action_name_prefix')
+            if self.should_use_action_name_prefix:
+                col.prop(self, 'action_name_prefix')
+
+        data_header, data_panel = layout.panel('data_panel_id', default_closed=False)
+        data_header.label(text='Data')
+
+        if data_panel:
+            col = data_panel.column(heading='Write')
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(self, 'should_write_keyframes')
+            col.prop(self, 'should_write_metadata')
+            col.prop(self, 'should_write_scale_keys')
+
+            if self.should_write_keyframes:
+                col = col.column(heading='Keyframes')
+                col.use_property_split = True
+                col.use_property_decorate = False
+                col.prop(self, 'should_convert_to_samples')
+
+        advanced_header, advanced_panel = layout.panel('advanced_panel_id', default_closed=True)
+        advanced_header.label(text='Advanced')
+
+        if advanced_panel:
+            bone_mapping_header, bone_mapping_panel = layout.panel('bone_mapping_id', default_closed=False)
+            bone_mapping_header.label(text='Bone Mapping')
+            if bone_mapping_panel:
+                col = bone_mapping_panel.column()
+                col.use_property_split = True
+                col.use_property_decorate = False
+                col.prop(self, 'bone_mapping_is_case_sensitive')
+                col.prop(self, 'bone_mapping_should_ignore_trailing_whitespace')
+
+            col = advanced_panel.column()
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(self, 'translation_scale', text='Translation Scale')
+
+            col = advanced_panel.column(heading='Options')
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(self, 'should_use_fake_user')
+            col.prop(self, 'should_stash')
+            col.prop(self, 'should_use_config_file')
+
+
+def draw_psa_import_options_no_panels(layout, pg: PsaImportMixin):
+    col = layout.column(heading='Sequences')
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(pg, 'fps_source')
+    if pg.fps_source == 'CUSTOM':
+        col.prop(pg, 'fps_custom')
+    col.prop(pg, 'should_overwrite')
+    col.prop(pg, 'should_use_action_name_prefix')
+    if pg.should_use_action_name_prefix:
+        col.prop(pg, 'action_name_prefix')
+
+    col = layout.column(heading='Write')
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(pg, 'should_write_keyframes')
+    col.prop(pg, 'should_write_metadata')
+    col.prop(pg, 'should_write_scale_keys')
+
+    if pg.should_write_keyframes:
+        col = col.column(heading='Keyframes')
+        col.use_property_split = True
+        col.use_property_decorate = False
+        col.prop(pg, 'should_convert_to_samples')
+
+    col = layout.column(heading='Bone Mapping')
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(pg, 'bone_mapping_is_case_sensitive')
+    col.prop(pg, 'bone_mapping_should_ignore_trailing_whitespace')
+
+    col = layout.column()
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(pg, 'translation_scale')
+
+    col = layout.column(heading='Options')
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(pg, 'should_use_fake_user')
+    col.prop(pg, 'should_stash')
+    col.prop(pg, 'should_use_config_file')
+
+
+_classes = (
+    PSA_OT_import_sequences_select_all,
+    PSA_OT_import_sequences_deselect_all,
+    PSA_OT_import_sequences_select_from_text,
+    PSA_OT_import,
+    PSA_OT_import_all,
+    PSA_OT_import_drag_and_drop,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psa/import_/properties.py

@@ -0,0 +1,187 @@
+import re
+from fnmatch import fnmatch
+
+from bpy.props import (
+    BoolProperty,
+    CollectionProperty,
+    EnumProperty,
+    FloatProperty,
+    IntProperty,
+    PointerProperty,
+    StringProperty,
+)
+from bpy.types import PropertyGroup, Text
+
+
+class PSA_PG_import_action_list_item(PropertyGroup):
+    action_name: StringProperty(options=set())
+    is_selected: BoolProperty(default=True, options=set())
+
+
+class PSA_PG_bone(PropertyGroup):
+    bone_name: StringProperty(options=set())
+
+
+class PSA_PG_data(PropertyGroup):
+    bones: CollectionProperty(type=PSA_PG_bone)
+    sequence_count: IntProperty(default=0)
+
+
+bone_mapping_items = (
+    ('EXACT', 'Exact', 'Bone names must match exactly.', 'EXACT', 0),
+    ('CASE_INSENSITIVE', 'Case Insensitive', 'Bones names must match, ignoring case (e.g., the bone PSA bone \'root\' can be mapped to the armature bone \'Root\')', 'CASE_INSENSITIVE', 1),
+)
+
+fps_source_items = (
+    ('SEQUENCE', 'Sequence', 'The sequence frame rate matches the original frame rate', 'ACTION', 0),
+    ('SCENE', 'Scene', 'The sequence is resampled to the frame rate of the scene', 'SCENE_DATA', 1),
+    ('CUSTOM', 'Custom', 'The sequence is resampled to a custom frame rate', 2),
+)
+
+compression_ratio_source_items = (
+    ('ACTION', 'Action', 'The compression ratio is sourced from the action metadata', 'ACTION', 0),
+    ('CUSTOM', 'Custom', 'The compression ratio is set to a custom value', 1),
+)
+
+class PsaImportMixin:
+    should_use_fake_user: BoolProperty(default=True, name='Fake User',
+                                       description='Assign each imported action a fake user so that the data block is '
+                                                   'saved even it has no users',
+                                       options=set())
+    should_use_config_file: BoolProperty(default=True, name='Use Config File',
+                                         description='Use the .config file that is sometimes generated when the PSA '
+                                                     'file is exported from UEViewer. This file contains '
+                                                     'options that can be used to filter out certain bones tracks '
+                                                     'from the imported actions',
+                                         options=set())
+    should_stash: BoolProperty(default=False, name='Stash',
+                               description='Stash each imported action as a strip on a new non-contributing NLA track',
+                               options=set())
+    should_use_action_name_prefix: BoolProperty(default=False, name='Prefix Action Name', options=set())
+    action_name_prefix: StringProperty(default='', name='Prefix', options=set())
+    should_overwrite: BoolProperty(default=False, name='Overwrite', options=set(),
+                                   description='If an action with a matching name already exists, the existing action '
+                                               'will have it\'s data overwritten instead of a new action being created')
+    should_write_keyframes: BoolProperty(default=True, name='Keyframes', options=set())
+    should_write_metadata: BoolProperty(default=True, name='Metadata', options=set(),
+                                        description='Additional data will be written to the custom properties of the '
+                                                    'Action (e.g., frame rate)')
+    should_write_scale_keys: BoolProperty(default=True, name='Scale Keys', options=set())
+    sequence_filter_name: StringProperty(default='', options={'TEXTEDIT_UPDATE'})
+    sequence_filter_is_selected: BoolProperty(default=False, options=set(), name='Only Show Selected',
+                                              description='Only show selected sequences')
+    sequence_use_filter_invert: BoolProperty(default=False, options=set())
+    sequence_use_filter_regex: BoolProperty(default=False, name='Regular Expression',
+                                            description='Filter using regular expressions', options=set())
+
+    should_convert_to_samples: BoolProperty(
+        default=False,
+        name='Convert to Samples',
+        description='Convert keyframes to read-only samples. '
+                    'Recommended if you do not plan on editing the actions directly'
+    )
+    bone_mapping_is_case_sensitive: BoolProperty(
+        default=False,
+        name='Case Sensitive'
+        )
+    bone_mapping_should_ignore_trailing_whitespace: BoolProperty(
+        default=True,
+        name='Ignore Trailing Whitespace'
+    )
+    fps_source: EnumProperty(name='FPS Source', items=fps_source_items)
+    fps_custom: FloatProperty(
+        default=30.0,
+        name='Custom FPS',
+        description='The frame rate to which the imported sequences will be resampled to',
+        options=set(),
+        min=1.0,
+        soft_min=1.0,
+        soft_max=60.0,
+        step=100,
+    )
+    compression_ratio_source: EnumProperty(name='Compression Ratio Source', items=compression_ratio_source_items, default='ACTION')
+    compression_ratio_custom: FloatProperty(
+        default=1.0,
+        name='Custom Compression Ratio',
+        description='The compression ratio to apply to the imported sequences',
+        options=set(),
+        min=0.0,
+        soft_min=0.0,
+        soft_max=1.0,
+        step=0.0625,
+    )
+    translation_scale: FloatProperty(
+        name='Translation Scale',
+        default=1.0,
+        description='Scale factor for bone translation values. Use this when the scale of the armature does not match the PSA file'
+    )
+
+
+# This property group lives "globally" in the scene, since Operators cannot have PointerProperty or CollectionProperty
+# properties.
+class PSA_PG_import(PropertyGroup):
+    psa_error: StringProperty(default='')
+    psa: PointerProperty(type=PSA_PG_data)
+    sequence_list: CollectionProperty(type=PSA_PG_import_action_list_item)
+    sequence_list_index: IntProperty(name='', default=0)
+    sequence_filter_name: StringProperty(default='', options={'TEXTEDIT_UPDATE'})
+    sequence_filter_is_selected: BoolProperty(default=False, options=set(), name='Only Show Selected',
+                                              description='Only show selected sequences')
+    sequence_use_filter_invert: BoolProperty(default=False, options=set())
+    sequence_use_filter_regex: BoolProperty(default=False, name='Regular Expression',
+                                            description='Filter using regular expressions', options=set())
+    select_text: PointerProperty(type=Text)
+
+
+def filter_sequences(pg: PSA_PG_import, sequences) -> list[int]:
+    bitflag_filter_item = 1 << 30
+    flt_flags = [bitflag_filter_item] * len(sequences)
+
+    if pg.sequence_filter_name is not None:
+        # Filter name is non-empty.
+        if pg.sequence_use_filter_regex:
+            # Use regular expression. If regex pattern doesn't compile, just ignore it.
+            try:
+                regex = re.compile(pg.sequence_filter_name)
+                for i, sequence in enumerate(sequences):
+                    if not regex.match(sequence.action_name):
+                        flt_flags[i] &= ~bitflag_filter_item
+            except re.error:
+                pass
+        else:
+            # User regular text matching.
+            for i, sequence in enumerate(sequences):
+                if not fnmatch(sequence.action_name, f'*{pg.sequence_filter_name}*'):
+                    flt_flags[i] &= ~bitflag_filter_item
+
+    if pg.sequence_filter_is_selected:
+        for i, sequence in enumerate(sequences):
+            if not sequence.is_selected:
+                flt_flags[i] &= ~bitflag_filter_item
+
+    if pg.sequence_use_filter_invert:
+        # Invert filter flags for all items.
+        for i, sequence in enumerate(sequences):
+            flt_flags[i] ^= bitflag_filter_item
+
+    return flt_flags
+
+
+def get_visible_sequences(pg: PSA_PG_import, sequences) -> list[PSA_PG_import_action_list_item]:
+    bitflag_filter_item = 1 << 30
+    visible_sequences = []
+    for i, flag in enumerate(filter_sequences(pg, sequences)):
+        if bool(flag & bitflag_filter_item):
+            visible_sequences.append(sequences[i])
+    return visible_sequences
+
+
+_classes = (
+    PSA_PG_import_action_list_item,
+    PSA_PG_bone,
+    PSA_PG_data,
+    PSA_PG_import,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psa/import_/properties.pyi

@@ -0,0 +1,60 @@
+from bpy.types import PropertyGroup, Text
+
+from ...shared.types import BpyCollectionProperty
+
+
+class PSA_PG_import_action_list_item:
+    action_name: str
+    is_selected: bool
+
+
+class PSA_PG_bone:
+    bone_name: str
+
+
+class PSA_PG_data(PropertyGroup):
+    bones: BpyCollectionProperty[PSA_PG_bone]
+    sequence_count: int
+
+class PsaImportMixin:
+    should_use_fake_user: bool
+    should_use_config_file: bool
+    should_stash: bool
+    should_use_action_name_prefix: bool
+    action_name_prefix: str
+    should_overwrite: bool
+    should_write_keyframes: bool
+    should_write_metadata: bool
+    should_write_scale_keys: bool
+    sequence_filter_name: str
+    sequence_filter_is_selected: bool
+    sequence_use_filter_invert: bool
+    sequence_use_filter_regex: bool
+    should_convert_to_samples: bool
+    bone_mapping_is_case_sensitive: bool
+    bone_mapping_should_ignore_trailing_whitespace: bool
+    fps_source: str
+    fps_custom: float
+    compression_ratio_source: str
+    compression_ratio_custom: float
+    translation_scale: float
+    
+class PSA_PG_import:
+    psa_error: str
+    psa: PSA_PG_data
+    sequence_list: BpyCollectionProperty[PSA_PG_import_action_list_item]
+    sequence_list_index: int
+    sequence_filter_name: str
+    sequence_filter_is_selected: bool
+    sequence_use_filter_invert: bool
+    sequence_use_filter_regex: bool
+    select_text: Text | None
+
+
+
+def filter_sequences(pg: PSA_PG_import, sequences) -> list[int]:
+    pass
+
+
+def get_visible_sequences(pg: PSA_PG_import, sequences) -> list[PSA_PG_import_action_list_item]:
+    pass

io_scene_psk_psa/psa/import_/ui.py

@@ -0,0 +1,52 @@
+import bpy
+from bpy.types import UIList
+
+from .properties import filter_sequences
+
+
+class PSA_UL_sequences_mixin(UIList):
+    def draw_item(self, context, layout, data, item, icon, active_data, active_property, index, flt_flag):
+        row = layout.row(align=True)
+        split = row.split(align=True, factor=0.75)
+        column = split.row(align=True)
+        column.alignment = 'LEFT'
+        column.prop(item, 'is_selected', icon_only=True)
+        column.label(text=getattr(item, 'action_name'))
+
+    def draw_filter(self, context, layout):
+        pg = getattr(context.scene, 'psa_import')
+        row = layout.row()
+        sub_row = row.row(align=True)
+        sub_row.prop(pg, 'sequence_filter_name', text='')
+        sub_row.prop(pg, 'sequence_use_filter_invert', text='', icon='ARROW_LEFTRIGHT')
+        sub_row.prop(pg, 'sequence_use_filter_regex', text='', icon='SORTBYEXT')
+        sub_row.prop(pg, 'sequence_filter_is_selected', text='', icon='CHECKBOX_HLT')
+
+    def filter_items(self, context, data, property):
+        pg = getattr(context.scene, 'psa_import')
+        sequences = getattr(data, property)
+        flt_flags = filter_sequences(pg, sequences)
+        flt_neworder = bpy.types.UI_UL_list.sort_items_by_name(sequences, 'action_name')
+        return flt_flags, flt_neworder
+
+
+class PSA_UL_sequences(PSA_UL_sequences_mixin):
+    pass
+
+
+class PSA_UL_import_sequences(PSA_UL_sequences_mixin):
+    pass
+
+
+class PSA_UL_import_actions(PSA_UL_sequences_mixin):
+    pass
+
+
+_classes = (
+    PSA_UL_sequences,
+    PSA_UL_import_sequences,
+    PSA_UL_import_actions,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psa/importer.py

@@ -0,0 +1,432 @@
+from typing import Sequence, Iterable, cast as typing_cast
+
+import bpy
+import numpy as np
+import re
+from bpy.types import Armature, Context, FCurve, Object, Bone, PoseBone
+from mathutils import Vector, Quaternion
+from bpy_extras import anim_utils
+
+from ..shared.types import PSX_PG_action_export
+
+from .config import PsaConfig, REMOVE_TRACK_LOCATION, REMOVE_TRACK_ROTATION
+from psk_psa_py.psa.reader import PsaReader
+from psk_psa_py.shared.data import PsxBone
+
+class BoneMapping:
+    def __init__(self,
+                 is_case_sensitive: bool = False,
+                 should_ignore_trailing_whitespace: bool = True
+                 ):
+        self.is_case_sensitive = is_case_sensitive
+        # Ancient PSK and PSA exporters would, for some reason, pad the bone names with spaces
+        # instead of just writing null bytes, probably because the programmers were lazy.
+        # By default, we will ignore trailing whitespace when doing comparisons.
+        self.should_ignore_trailing_whitespace = should_ignore_trailing_whitespace
+
+
+class PsaImportOptions(object):
+    def __init__(self,
+                 action_name_prefix: str = '',
+                 bone_mapping: BoneMapping = BoneMapping(),
+                 fps_custom: float = 30.0,
+                 fps_source: str = 'SEQUENCE',
+                 psa_config: PsaConfig = PsaConfig(),
+                 sequence_names: list[str] | None = None,
+                 should_convert_to_samples: bool = False,
+                 should_overwrite: bool = False,
+                 should_stash: bool = False,
+                 should_use_config_file: bool = True,
+                 should_use_fake_user: bool = False,
+                 should_write_keyframes: bool = True,
+                 should_write_metadata: bool = True,
+                 should_write_scale_keys: bool = True,
+                 translation_scale: float = 1.0
+                 ):
+        self.action_name_prefix = action_name_prefix
+        self.bone_mapping = bone_mapping
+        self.fps_custom = fps_custom
+        self.fps_source = fps_source
+        self.psa_config = psa_config
+        self.sequence_names = sequence_names if sequence_names is not None else []
+        self.should_convert_to_samples = should_convert_to_samples
+        self.should_overwrite = should_overwrite
+        self.should_stash = should_stash
+        self.should_use_config_file = should_use_config_file
+        self.should_use_fake_user = should_use_fake_user
+        self.should_write_keyframes = should_write_keyframes
+        self.should_write_metadata = should_write_metadata
+        self.should_write_scale_keys = should_write_scale_keys
+        self.translation_scale = translation_scale
+
+
+class ImportBone(object):
+    def __init__(self, psa_bone: PsxBone):
+        self.psa_bone: PsxBone = psa_bone
+        self.parent: ImportBone | None = None
+        self.armature_bone: Bone | None = None
+        self.pose_bone: PoseBone | None = None
+        self.original_location: Vector = Vector()
+        self.original_rotation: Quaternion = Quaternion()
+        self.post_rotation: Quaternion = Quaternion()
+        self.fcurves: list[FCurve] = []
+
+
+def _calculate_fcurve_data(import_bone: ImportBone, key_data: Sequence[float]):
+    # Convert world-space transforms to local-space transforms.
+    key_rotation = Quaternion(key_data[0:4])
+    key_location = Vector(key_data[4:7])
+    q = import_bone.post_rotation.copy()
+    q.rotate(import_bone.original_rotation)
+    rotation = q
+    q = import_bone.post_rotation.copy()
+    if import_bone.parent is None:
+        q.rotate(key_rotation.conjugated())
+    else:
+        q.rotate(key_rotation)
+    rotation.rotate(q.conjugated())
+    location = key_location - import_bone.original_location
+    location.rotate(import_bone.post_rotation.conjugated())
+    scale = Vector(key_data[7:10])
+    return rotation.w, rotation.x, rotation.y, rotation.z, location.x, location.y, location.z, scale.x, scale.y, scale.z
+
+
+class PsaImportResult:
+    def __init__(self):
+        self.warnings: list[str] = []
+
+
+def _get_armature_bone_index_for_psa_bone(psa_bone_name: str, armature_bone_names: list[str], bone_mapping: BoneMapping) -> int | None:
+    """
+    @param psa_bone_name: The name of the PSA bone.
+    @param armature_bone_names: The names of the bones in the armature.
+    @param bone_mapping: Bone mapping information.
+    @return: The index of the armature bone that corresponds to the given PSA bone, or None if no such bone exists.
+    """
+    # Use regular expressions for bone name matching.
+    pattern = psa_bone_name
+    flags = 0
+
+    if bone_mapping.should_ignore_trailing_whitespace:
+        psa_bone_name = psa_bone_name.rstrip()
+        pattern += r'\s*'
+    
+    if not bone_mapping.is_case_sensitive:
+        flags = re.IGNORECASE
+    
+    pattern = re.compile(pattern, flags)
+
+    for armature_bone_index, armature_bone_name in enumerate(armature_bone_names):
+        if re.fullmatch(pattern, armature_bone_name):
+            return armature_bone_index
+
+    return None
+
+
+def _resample_sequence_data_matrix(sequence_data_matrix: np.ndarray, frame_step: float = 1.0) -> np.ndarray:
+    """
+    Resamples the sequence data matrix to the target frame count.
+
+    @param sequence_data_matrix: FxBx7 matrix where F is the number of frames, B is the number of bones, and X is the
+    number of data elements per bone.
+    @param frame_step: The step between frames in the resampled sequence.
+    @return: The resampled sequence data matrix, or sequence_data_matrix if no resampling is necessary.
+    """
+
+    def _get_sample_frame_times(source_frame_count: int, frame_step: float) -> Iterable[float]:
+        # TODO: for correctness, we should also emit the target frame time as well (because the last frame can be a
+        #  fractional frame).
+        assert frame_step > 0.0, 'Frame step must be greater than 0'
+        time = 0.0
+        while time < source_frame_count - 1:
+            yield time
+            time += frame_step
+        yield source_frame_count - 1
+
+    if frame_step == 1.0:
+        # No resampling is necessary.
+        return sequence_data_matrix
+
+    source_frame_count, bone_count = sequence_data_matrix.shape[:2]
+    sample_frame_times = list(_get_sample_frame_times(source_frame_count, frame_step))
+    target_frame_count = len(sample_frame_times)
+    resampled_sequence_data_matrix = np.zeros((target_frame_count, bone_count, 7), dtype=float)
+
+    for sample_frame_index, sample_frame_time in enumerate(sample_frame_times):
+        frame_index = int(sample_frame_time)
+        if sample_frame_time % 1.0 == 0.0:
+            # Sample time has no fractional part, so just copy the frame.
+            resampled_sequence_data_matrix[sample_frame_index, :, :] = sequence_data_matrix[frame_index, :, :]
+        else:
+            # Sample time has a fractional part, so interpolate between two frames.
+            next_frame_index = frame_index + 1
+            for bone_index in range(bone_count):
+                source_frame_1_data = sequence_data_matrix[frame_index, bone_index, :]
+                source_frame_2_data = sequence_data_matrix[next_frame_index, bone_index, :]
+                factor = sample_frame_time - frame_index
+                q = Quaternion((source_frame_1_data[:4])).slerp(Quaternion((source_frame_2_data[:4])), factor)
+                q.normalize()
+                l = Vector(source_frame_1_data[4:]).lerp(Vector(source_frame_2_data[4:]), factor)
+                resampled_sequence_data_matrix[sample_frame_index, bone_index, :] = q.w, q.x, q.y, q.z, l.x, l.y, l.z
+
+    return resampled_sequence_data_matrix
+
+
+def _read_sequence_data_matrix(psa_reader: PsaReader, sequence_name: str) -> np.ndarray:
+    """
+    Reads and returns the data matrix for the given sequence.
+    The order of the data in the third axis is Qw, Qx, Qy, Qz, Lx, Ly, Lz, Sx, Sy, Sz
+    
+    @param sequence_name: The name of the sequence.
+    @return: An FxBx10 matrix where F is the number of frames, B is the number of bones.
+    """
+    sequence = psa_reader.sequences[sequence_name]
+    keys = psa_reader.read_sequence_keys(sequence_name)
+    bone_count = len(psa_reader.bones)
+    matrix_size = sequence.frame_count, bone_count, 10
+    matrix = np.ones(matrix_size)
+    keys_iter = iter(keys)
+    # Populate rotation and location data.
+    for frame_index in range(sequence.frame_count):
+        for bone_index in range(bone_count):
+            matrix[frame_index, bone_index, :7] = list(next(keys_iter).data)
+    # Populate scale data, if it exists.
+    scale_keys = psa_reader.read_sequence_scale_keys(sequence_name)
+    if len(scale_keys) > 0:
+        scale_keys_iter = iter(scale_keys)
+        for frame_index in range(sequence.frame_count):
+            for bone_index in range(bone_count):
+                matrix[frame_index, bone_index, 7:] = list(next(scale_keys_iter).data)
+    return matrix
+
+
+def import_psa(context: Context, psa_reader: PsaReader, armature_object: Object, options: PsaImportOptions) -> PsaImportResult:
+
+    assert context.window_manager
+
+    result = PsaImportResult()
+    sequences = [psa_reader.sequences[x] for x in options.sequence_names]
+    armature_data = typing_cast(Armature, armature_object.data)
+
+    # Create an index mapping from bones in the PSA to bones in the target armature.
+    psa_to_armature_bone_indices = {}
+    armature_to_psa_bone_indices = {}
+    armature_bone_names = [x.name for x in armature_data.bones]
+    psa_bone_names = []
+    duplicate_mappings = []
+
+    for psa_bone_index, psa_bone in enumerate(psa_reader.bones):
+        psa_bone_name: str = psa_bone.name.decode('windows-1252')
+        armature_bone_index = _get_armature_bone_index_for_psa_bone(psa_bone_name, armature_bone_names, options.bone_mapping)
+        if armature_bone_index is not None:
+            # Ensure that no other PSA bone has been mapped to this armature bone yet.
+            if armature_bone_index not in armature_to_psa_bone_indices:
+                psa_to_armature_bone_indices[psa_bone_index] = armature_bone_index
+                armature_to_psa_bone_indices[armature_bone_index] = psa_bone_index
+            else:
+                # This armature bone has already been mapped to a PSA bone.
+                duplicate_mappings.append((psa_bone_index, armature_bone_index, armature_to_psa_bone_indices[armature_bone_index]))
+            psa_bone_names.append(armature_bone_names[armature_bone_index])
+        else:
+            psa_bone_names.append(psa_bone_name)
+
+    # Warn about duplicate bone mappings.
+    if len(duplicate_mappings) > 0:
+        for (psa_bone_index, armature_bone_index, mapped_psa_bone_index) in duplicate_mappings:
+            psa_bone_name = psa_bone_names[psa_bone_index]
+            armature_bone_name = armature_bone_names[armature_bone_index]
+            mapped_psa_bone_name = psa_bone_names[mapped_psa_bone_index]
+            result.warnings.append(f'PSA bone {psa_bone_index} ({psa_bone_name}) could not be mapped to armature bone {armature_bone_index} ({armature_bone_name}) because the armature bone is already mapped to PSA bone {mapped_psa_bone_index} ({mapped_psa_bone_name})')
+
+    # Report if there are missing bones in the target armature.
+    missing_bone_names = set(psa_bone_names).difference(set(armature_bone_names))
+    if len(missing_bone_names) > 0:
+        result.warnings.append(
+            f'The armature \'{armature_object.name}\' is missing {len(missing_bone_names)} bones that exist in '
+            'the PSA:\n' +
+            str(list(sorted(missing_bone_names)))
+        )
+    del armature_bone_names
+
+    assert armature_object.pose
+
+    # Create intermediate bone data for import operations.
+    import_bones = []
+    psa_bone_names_to_import_bones = dict()
+
+    for (psa_bone_index, psa_bone), psa_bone_name in zip(enumerate(psa_reader.bones), psa_bone_names):
+        if psa_bone_index not in psa_to_armature_bone_indices:
+            # PSA bone does not map to armature bone, skip it and leave an empty bone in its place.
+            import_bones.append(None)
+            continue
+        import_bone = ImportBone(psa_bone)
+        import_bone.armature_bone = armature_data.bones[psa_bone_name]
+        import_bone.pose_bone = armature_object.pose.bones[psa_bone_name]
+        psa_bone_names_to_import_bones[psa_bone_name] = import_bone
+        import_bones.append(import_bone)
+
+    bones_with_missing_parents = []
+
+    for import_bone in filter(lambda x: x is not None, import_bones):
+        armature_bone = import_bone.armature_bone
+        has_parent = armature_bone.parent is not None
+        if has_parent:
+            if armature_bone.parent.name in psa_bone_names:
+                import_bone.parent = psa_bone_names_to_import_bones[armature_bone.parent.name]
+            else:
+                # Add a warning if the parent bone is not in the PSA.
+                bones_with_missing_parents.append(armature_bone)
+        # Calculate the original location & rotation of each bone (in world-space maybe?)
+        if has_parent:
+            import_bone.original_location = armature_bone.matrix_local.translation - armature_bone.parent.matrix_local.translation
+            import_bone.original_location.rotate(armature_bone.parent.matrix_local.to_quaternion().conjugated())
+            import_bone.original_rotation = armature_bone.matrix_local.to_quaternion()
+            import_bone.original_rotation.rotate(armature_bone.parent.matrix_local.to_quaternion().conjugated())
+            import_bone.original_rotation.conjugate()
+        else:
+            import_bone.original_location = armature_bone.matrix_local.translation.copy()
+            import_bone.original_rotation = armature_bone.matrix_local.to_quaternion().conjugated()
+
+        import_bone.post_rotation = import_bone.original_rotation.conjugated()
+
+    # Warn about bones with missing parents.
+    if len(bones_with_missing_parents) > 0:
+        count = len(bones_with_missing_parents)
+        message = f'{count} bone(s) have parents that are not present in the PSA:\n' + str([x.name for x in bones_with_missing_parents])
+        result.warnings.append(message)
+
+    context.window_manager.progress_begin(0, len(sequences))
+
+    # Create and populate the data for new sequences.
+    actions = []
+    for sequence_index, sequence in enumerate(sequences):
+        # Add the action.
+        sequence_name = sequence.name.decode('windows-1252')
+        action_name = options.action_name_prefix + sequence_name
+
+        # Get the bone track flags for this sequence, or an empty dictionary if none exist.
+        sequence_bone_track_flags = dict()
+        if sequence_name in options.psa_config.sequence_bone_flags.keys():
+            sequence_bone_track_flags = options.psa_config.sequence_bone_flags[sequence_name]
+
+        if options.should_overwrite and action_name in bpy.data.actions:
+            action = bpy.data.actions[action_name]
+        else:
+            action = bpy.data.actions.new(name=action_name)
+            action_slot = action.slots.new('OBJECT', armature_object.name)
+
+        # TODO: Wish there was a better way to do this.
+        action_slot = action.slots[f'OB{armature_object.name}']
+
+        assert action_slot
+
+        # Calculate the target FPS.
+        match options.fps_source:
+            case 'CUSTOM':
+                target_fps = options.fps_custom
+            case 'SCENE':
+                assert context.scene
+                target_fps = context.scene.render.fps
+            case 'SEQUENCE':
+                target_fps = sequence.fps
+            case _:
+                assert False, f'Invalid FPS source: {options.fps_source}'
+
+        if options.should_write_keyframes:            
+            channelbag = anim_utils.action_ensure_channelbag_for_slot(action, action_slot)
+
+            # Create f-curves for the rotation and location of each bone.
+            for psa_bone_index, armature_bone_index in psa_to_armature_bone_indices.items():
+                bone_track_flags = sequence_bone_track_flags.get(psa_bone_index, 0)
+                import_bone = import_bones[psa_bone_index]
+                pose_bone = import_bone.pose_bone
+                rotation_data_path = pose_bone.path_from_id('rotation_quaternion')
+                location_data_path = pose_bone.path_from_id('location')
+                scale_data_path = pose_bone.path_from_id('scale')
+                add_rotation_fcurves = (bone_track_flags & REMOVE_TRACK_ROTATION) == 0
+                add_location_fcurves = (bone_track_flags & REMOVE_TRACK_LOCATION) == 0
+                add_scale_fcurves = psa_reader.has_scale_keys and options.should_write_scale_keys
+                import_bone.fcurves = [
+                    channelbag.fcurves.ensure(rotation_data_path, index=0, group_name=pose_bone.name) if add_rotation_fcurves else None,  # Qw
+                    channelbag.fcurves.ensure(rotation_data_path, index=1, group_name=pose_bone.name) if add_rotation_fcurves else None,  # Qx
+                    channelbag.fcurves.ensure(rotation_data_path, index=2, group_name=pose_bone.name) if add_rotation_fcurves else None,  # Qy
+                    channelbag.fcurves.ensure(rotation_data_path, index=3, group_name=pose_bone.name) if add_rotation_fcurves else None,  # Qz
+                    channelbag.fcurves.ensure(location_data_path, index=0, group_name=pose_bone.name) if add_location_fcurves else None,  # Lx
+                    channelbag.fcurves.ensure(location_data_path, index=1, group_name=pose_bone.name) if add_location_fcurves else None,  # Ly
+                    channelbag.fcurves.ensure(location_data_path, index=2, group_name=pose_bone.name) if add_location_fcurves else None,  # Lz
+                    channelbag.fcurves.ensure(scale_data_path,    index=0, group_name=pose_bone.name) if add_scale_fcurves    else None,  # Sx
+                    channelbag.fcurves.ensure(scale_data_path,    index=1, group_name=pose_bone.name) if add_scale_fcurves    else None,  # Sy
+                    channelbag.fcurves.ensure(scale_data_path,    index=2, group_name=pose_bone.name) if add_scale_fcurves    else None,  # Sz
+                ]
+
+            # Read the sequence data matrix from the PSA.
+            sequence_data_matrix = _read_sequence_data_matrix(psa_reader, sequence_name)
+
+            if options.translation_scale != 1.0:
+                # Scale the translation data.
+                sequence_data_matrix[:, :, 4:7] *= options.translation_scale
+
+            # Convert the sequence's data from world-space to local-space.
+            for bone_index, import_bone in enumerate(import_bones):
+                if import_bone is None:
+                    continue
+                for frame_index in range(sequence.frame_count):
+                    # This bone has writeable keyframes for this frame.
+                    key_data = sequence_data_matrix[frame_index, bone_index]
+                    # Calculate the local-space key data for the bone.
+                    sequence_data_matrix[frame_index, bone_index] = _calculate_fcurve_data(import_bone, key_data)
+
+            # Resample the sequence data to the target FPS.
+            # If the target frame count is the same as the source frame count, this will be a no-op.
+            resampled_sequence_data_matrix = _resample_sequence_data_matrix(sequence_data_matrix,
+                                                                            frame_step=sequence.fps / target_fps)
+
+            # Write the keyframes out.
+            # Note that the f-curve data consists of alternating time and value data.
+            target_frame_count = resampled_sequence_data_matrix.shape[0]
+            fcurve_data = np.zeros(2 * target_frame_count, dtype=float)
+            fcurve_data[0::2] = range(0, target_frame_count)
+
+            for bone_index, import_bone in enumerate(import_bones):
+                if import_bone is None:
+                    continue
+                for fcurve_index, fcurve in enumerate(import_bone.fcurves):
+                    if fcurve is None:
+                        continue
+                    fcurve.keyframe_points.clear()
+                    fcurve_data[1::2] = resampled_sequence_data_matrix[:, bone_index, fcurve_index]
+                    fcurve.keyframe_points.add(target_frame_count)
+                    fcurve.keyframe_points.foreach_set('co', fcurve_data)
+                    for fcurve_keyframe in fcurve.keyframe_points:
+                        fcurve_keyframe.interpolation = 'LINEAR'
+
+            if options.should_convert_to_samples:
+                # Bake the curve to samples.
+                for fcurve in channelbag.fcurves:
+                    fcurve.convert_to_samples(start=0, end=sequence.frame_count)
+
+        # Write meta-data.
+        if options.should_write_metadata:
+            pg = typing_cast(PSX_PG_action_export, getattr(action, 'psa_export'))
+            pg.fps = target_fps
+
+        action.use_fake_user = options.should_use_fake_user
+
+        actions.append(action)
+
+        context.window_manager.progress_update(sequence_index)
+
+    # If the user specifies, store the new animations as strips on a non-contributing NLA track.
+    if options.should_stash:
+        animation_data = armature_object.animation_data
+        if animation_data is None:
+            animation_data = armature_object.animation_data_create()
+        for action in actions:
+            nla_track = animation_data.nla_tracks.new()
+            nla_track.name = action.name
+            nla_track.mute = True
+            nla_track.strips.new(name=action.name, start=0, action=action)
+
+    context.window_manager.progress_end()
+
+    return result

io_scene_psk_psa/psk/builder.py

@@ -0,0 +1,414 @@
+import bmesh
+import bpy
+import numpy as np
+from bpy.types import Armature, Context, Object, Mesh
+from mathutils import Matrix, Quaternion
+from typing import Iterable, cast as typing_cast
+from psk_psa_py.shared.data import PsxBone, Vector3
+from psk_psa_py.psk.data import Psk
+from .properties import triangle_type_and_bit_flags_to_poly_flags
+from ..shared.helpers import (
+    ObjectNode,
+    ObjectTree,
+    PskInputObjects,
+    PsxBoneCollection,
+    convert_bpy_quaternion_to_psx_quaternion,
+    convert_string_to_cp1252_bytes,
+    create_psx_bones,
+    get_armature_for_mesh_object,
+    get_coordinate_system_transform,
+    get_materials_for_mesh_objects,
+)
+
+
+class PskBuildOptions(object):
+    def __init__(self):
+        self.bone_filter_mode = 'ALL'
+        self.bone_collection_indices: list[PsxBoneCollection] = []
+        self.object_eval_state = 'EVALUATED'
+        self.material_order_mode = 'AUTOMATIC'
+        self.material_name_list: list[str] = []
+        self.scale = 1.0
+        self.export_space = 'WORLD'
+        self.forward_axis = 'X'
+        self.up_axis = 'Z'
+
+
+class PskBuildResult(object):
+    def __init__(self, psk: Psk, warnings: list[str]):
+        self.psk: Psk = psk
+        self.warnings: list[str] = warnings
+
+
+def _get_mesh_export_space_matrix(node: ObjectNode | None, export_space: str) -> Matrix:
+    if node is None:
+        return Matrix.Identity(4)
+    
+    armature_object = node.object
+    root_armature_object = node.root.object
+
+    def get_object_space_matrix(obj: Object) -> Matrix:
+        translation, rotation, _ = obj.matrix_world.decompose()
+        # We neutralize the scale here because the scale is already applied to the mesh objects implicitly.
+        return Matrix.Translation(translation) @ rotation.to_matrix().to_4x4()
+
+    armature_space_matrix = get_object_space_matrix(armature_object)
+    root_armature_space_matrix = get_object_space_matrix(root_armature_object)
+    relative_matrix = root_armature_space_matrix @ armature_space_matrix.inverted()
+
+    match export_space:
+        case 'WORLD':
+            return Matrix.Identity(4)
+        case 'ARMATURE':
+            return (armature_space_matrix @ relative_matrix).inverted()
+        case 'ROOT':
+            root_armature_data = typing_cast(Armature, root_armature_object.data)
+            if len(root_armature_data.bones) == 0:
+                raise RuntimeError(f'Armature {root_armature_data.name} has no bones')
+            return (armature_space_matrix @ relative_matrix @ root_armature_data.bones[0].matrix_local).inverted()
+        case _:
+            assert False, f'Invalid export space: {export_space}'
+
+
+def _get_material_name_indices(obj: Object, material_names: list[str]) -> Iterable[int]:
+    """
+    Returns the index of the material in the list of material names.
+    If the material is not found or the slot is empty, the index of 'None' is returned.
+    """
+    for material_slot in obj.material_slots:
+        try:
+            material_name = material_slot.material.name if material_slot.material is not None else 'None'
+            yield material_names.index(material_name)
+        except ValueError:
+            yield 0
+
+
+def build_psk(context: Context, input_objects: PskInputObjects, options: PskBuildOptions) -> PskBuildResult:
+
+    assert context.window_manager
+
+    armature_objects = list(input_objects.armature_objects)
+    armature_object_tree = ObjectTree(input_objects.armature_objects)    
+
+    warnings: list[str] = []
+    psk = Psk()
+
+    psx_bone_create_result = create_psx_bones(
+        armature_objects=armature_objects,
+        export_space=options.export_space,
+        forward_axis=options.forward_axis,
+        up_axis=options.up_axis,
+        scale=options.scale,
+        bone_filter_mode=options.bone_filter_mode,
+        bone_collection_indices=options.bone_collection_indices
+    )
+
+    psk.bones = [bone.psx_bone for bone in psx_bone_create_result.bones]
+
+    if len(psk.bones) == 0:
+        # Add a default root bone if there are no bones to export.
+        # This is necessary because Unreal Engine requires at least one bone in the PSK file.
+        psx_bone = PsxBone()
+        psx_bone.name = b'ROOT'
+        psx_bone.rotation = convert_bpy_quaternion_to_psx_quaternion(Quaternion())
+        psk.bones.append(psx_bone)
+
+    # Materials
+    mesh_objects = [dfs_object.obj for dfs_object in input_objects.mesh_dfs_objects]
+    
+    match options.material_order_mode:
+        case 'AUTOMATIC':
+            materials = list(get_materials_for_mesh_objects(context.evaluated_depsgraph_get(), mesh_objects))
+        case 'MANUAL':
+            # The material name list may contain materials that are not on the mesh objects.
+            # Therefore, we can take the material_name_list as gospel and simply use it as a lookup table.
+            # If a look-up fails, replace it with an empty material.
+            materials = [bpy.data.materials.get(x, None) for x in options.material_name_list]
+            
+            # Check if any mesh needs a None material (has no slots or empty slots)
+            needs_none_material = False
+            for mesh_object in mesh_objects:
+                evaluated_mesh_object = mesh_object.evaluated_get(context.evaluated_depsgraph_get())
+                if len(evaluated_mesh_object.material_slots) == 0:
+                    needs_none_material = True
+                    break
+                for material_slot in evaluated_mesh_object.material_slots:
+                    if material_slot.material is None:
+                        needs_none_material = True
+                        break
+                if needs_none_material:
+                    break
+            
+            # Append None at the end if needed and not already present
+            if needs_none_material and None not in materials:
+                materials.append(None)
+        case _:
+            assert False, f'Invalid material order mode: {options.material_order_mode}'
+
+    for material in materials:
+        psk_material = Psk.Material()
+        psk_material.name = convert_string_to_cp1252_bytes(material.name if material else 'None')
+        psk_material.texture_index = len(psk.materials)
+        if material is not None:
+            psk_material.poly_flags = triangle_type_and_bit_flags_to_poly_flags(material.psk.mesh_triangle_type,
+                                                                                material.psk.mesh_triangle_bit_flags)
+        psk.materials.append(psk_material)
+
+    # Ensure at least one material exists
+    if len(psk.materials) == 0:
+        # Add a default material if no materials are present.
+        psk_material = Psk.Material()
+        psk_material.name = convert_string_to_cp1252_bytes('None')
+        psk.materials.append(psk_material)
+
+    context.window_manager.progress_begin(0, len(input_objects.mesh_dfs_objects))
+    coordinate_system_matrix = get_coordinate_system_transform(options.forward_axis, options.up_axis)
+    root_armature_object = next(iter(armature_object_tree), None)
+
+    # Calculate the export spaces for the armature objects.
+    # This is used later to transform the mesh object geometry into the export space.
+    armature_mesh_export_space_matrices: dict[Object | None, Matrix] = {None: Matrix.Identity(4)}
+
+    if options.export_space == 'ARMATURE':
+        # For meshes without an armature modifier, we need to set the export space to the first armature object.
+        armature_mesh_export_space_matrices[None] = _get_mesh_export_space_matrix(root_armature_object, options.export_space)
+    
+    # TODO: also handle the case of multiple roots; dont' just assume we have one!
+    for armature_node in iter(armature_object_tree):
+        armature_mesh_export_space_matrices[armature_node.object] = _get_mesh_export_space_matrix(armature_node, options.export_space)
+    
+    # Temporarily force the armature into the rest position.
+    # The original pose position setting will be restored at the end.
+    original_armature_object_pose_positions = {a: a.data.pose_position for a in armature_objects}
+    for armature_object in armature_objects:
+        armature_data = typing_cast(Armature, armature_object.data)
+        armature_data.pose_position = 'REST'
+
+    material_names = [m.name if m is not None else 'None' for m in materials]
+
+    scale_matrix = Matrix.Scale(options.scale, 4)
+
+    for object_index, input_mesh_object in enumerate(input_objects.mesh_dfs_objects):
+        obj, matrix_world = input_mesh_object.obj, input_mesh_object.matrix_world
+        armature_object = get_armature_for_mesh_object(obj)
+        should_flip_normals = False
+
+        # Material indices
+        material_indices = list(_get_material_name_indices(obj, material_names))
+
+        if len(material_indices) == 0:
+            # If the mesh has no material slots, map to the 'None' material index
+            try:
+                none_material_index = material_names.index('None')
+            except ValueError:
+                none_material_index = 0
+            material_indices = [none_material_index]
+
+        # Store the reference to the evaluated object and data so that we can clean them up later.
+        evaluated_mesh_object = None
+        evaluated_mesh_data = None
+
+        # Mesh data
+        match options.object_eval_state:
+            case 'ORIGINAL':
+                mesh_object = obj
+                mesh_data = typing_cast(Mesh, obj.data)
+            case 'EVALUATED':
+                # Create a copy of the mesh object after non-armature modifiers are applied.
+                depsgraph = context.evaluated_depsgraph_get()
+                bm = bmesh.new()
+
+                try:
+                    bm.from_object(obj, depsgraph)
+                except ValueError as e:
+                    del bm
+                    raise RuntimeError(f'Object "{obj.name}" is not evaluated.\n'
+                    'This is likely because the object is in a collection that has been excluded from the view layer.') from e
+
+                evaluated_mesh_data = bpy.data.meshes.new('')
+                mesh_data = evaluated_mesh_data
+                bm.to_mesh(mesh_data)
+                del bm
+                evaluated_mesh_object = bpy.data.objects.new('', mesh_data)
+                mesh_object = evaluated_mesh_object
+                mesh_object.matrix_world = matrix_world
+
+                # Extract the scale from the matrix.
+                _, _, scale = matrix_world.decompose()
+
+                # Negative scaling in Blender results in inverted normals after the scale is applied. However, if the
+                # scale is not applied, the normals will appear unaffected in the viewport. The evaluated mesh data used
+                # in the export will have the scale applied, but this behavior is not obvious to the user.
+                #
+                # In order to have the exporter be as WYSIWYG as possible, we need to check for negative scaling and
+                # invert the normals if necessary. If two axes have negative scaling and the third has positive scaling,
+                # the normals will be correct. We can detect this by checking if the number of negative scaling axes is
+                # odd. If it is, we need to invert the normals of the mesh by swapping the order of the vertices in each
+                # face.
+                if not should_flip_normals:
+                    should_flip_normals = sum(1 for x in scale if x < 0) % 2 == 1
+
+                # Copy the vertex groups
+                for vertex_group in obj.vertex_groups:
+                    mesh_object.vertex_groups.new(name=vertex_group.name)
+            case _:
+                assert False, f'Invalid object evaluation state: {options.object_eval_state}'
+
+        match options.export_space:
+            case 'ARMATURE' | 'ROOT':
+                mesh_export_space_matrix = armature_mesh_export_space_matrices[armature_object]
+            case 'WORLD':
+                mesh_export_space_matrix = armature_mesh_export_space_matrices[armature_object]
+            case _:
+                assert False, f'Invalid export space: {options.export_space}'
+
+        vertex_transform_matrix = scale_matrix @ coordinate_system_matrix.inverted() @ mesh_export_space_matrix
+        point_transform_matrix = vertex_transform_matrix @ mesh_object.matrix_world
+
+        # Vertices
+        vertex_offset = len(psk.points)
+        for vertex in mesh_data.vertices:
+            point = Vector3()
+            v = point_transform_matrix @ vertex.co
+            point.x = v.x
+            point.y = v.y
+            point.z = v.z
+            psk.points.append(point)
+
+        # Wedges
+        mesh_data.calc_loop_triangles()
+
+        if mesh_data.uv_layers.active is None:
+            warnings.append(f'"{mesh_object.name}" has no active UV Map')
+
+        # Build a list of non-unique wedges.
+        wedges = []
+        if mesh_data.uv_layers.active:
+            uv_layer = mesh_data.uv_layers.active.data
+            for loop_index, loop in enumerate(mesh_data.loops):
+                wedges.append(Psk.Wedge(
+                    point_index=loop.vertex_index + vertex_offset,
+                    u=uv_layer[loop_index].uv[0],
+                    v=1.0 - uv_layer[loop_index].uv[1]
+                ))
+        else:
+            for loop_index, loop in enumerate(mesh_data.loops):
+                wedges.append(Psk.Wedge(point_index=loop.vertex_index + vertex_offset, u=0.0, v=0.0))
+
+
+        # Assign material indices to the wedges.
+        for triangle in mesh_data.loop_triangles:
+            for loop_index in triangle.loops:
+                wedges[loop_index].material_index = material_indices[triangle.material_index]
+
+        # Populate the list of wedges with unique wedges & build a look-up table of loop indices to wedge indices.
+        wedge_indices = dict()
+        loop_wedge_indices = np.full(len(mesh_data.loops), -1)
+        for loop_index, wedge in enumerate(wedges):
+            wedge_hash = hash(wedge)
+            if wedge_hash in wedge_indices:
+                loop_wedge_indices[loop_index] = wedge_indices[wedge_hash]
+            else:
+                wedge_index = len(psk.wedges)
+                wedge_indices[wedge_hash] = wedge_index
+                psk.wedges.append(wedge)
+                loop_wedge_indices[loop_index] = wedge_index
+
+        # Faces
+        poly_groups, groups = mesh_data.calc_smooth_groups(use_bitflags=True)
+        psk_face_start_index = len(psk.faces)
+        for f in mesh_data.loop_triangles:
+            face = Psk.Face(
+                wedge_indices=(loop_wedge_indices[f.loops[2]], loop_wedge_indices[f.loops[1]], loop_wedge_indices[f.loops[0]]),
+                material_index=material_indices[f.material_index],
+                smoothing_groups=poly_groups[f.polygon_index],
+            )
+            psk.faces.append(face)
+
+        if should_flip_normals:
+            # Invert the normals of the faces.
+            for face in psk.faces[psk_face_start_index:]:
+                face.wedge_indices = (face.wedge_indices[2], face.wedge_indices[1], face.wedge_indices[0])
+
+        # Weights
+        if armature_object is not None:
+            armature_data = typing_cast(Armature, armature_object.data)
+            bone_index_offset = psx_bone_create_result.armature_object_root_bone_indices[armature_object]
+            # Because the vertex groups may contain entries for which there is no matching bone in the armature,
+            # we must filter them out and not export any weights for these vertex groups.
+
+            bone_names = psx_bone_create_result.armature_object_bone_names[armature_object]
+            vertex_group_names = [x.name for x in mesh_object.vertex_groups]
+            vertex_group_bone_indices: dict[int, int] = dict()
+            for vertex_group_index, vertex_group_name in enumerate(vertex_group_names):
+                try:
+                    vertex_group_bone_indices[vertex_group_index] = bone_names.index(vertex_group_name) + bone_index_offset
+                except ValueError:
+                    # The vertex group does not have a matching bone in the list of bones to be exported.
+                    # Check to see if there is an associated bone for this vertex group that exists in the armature.
+                    # If there is, we can traverse the ancestors of that bone to find an alternate bone to use for
+                    # weighting the vertices belonging to this vertex group.
+                    if vertex_group_name in armature_data.bones:
+                        bone = armature_data.bones[vertex_group_name]
+                        while bone is not None:
+                            try:
+                                vertex_group_bone_indices[vertex_group_index] = bone_names.index(bone.name) + bone_index_offset
+                                break
+                            except ValueError:
+                                bone = bone.parent
+
+            # Keep track of which vertices have been assigned weights.
+            # The ones that have not been assigned weights will be assigned to the root bone.
+            # Without this, some older versions of UnrealEd may have corrupted meshes.
+            vertices_assigned_weights = np.full(len(mesh_data.vertices), False)
+
+            for vertex_group_index, vertex_group in enumerate(mesh_object.vertex_groups):
+                if vertex_group_index not in vertex_group_bone_indices:
+                    # Vertex group has no associated bone, skip it.
+                    continue
+                bone_index = vertex_group_bone_indices[vertex_group_index]
+                for vertex_index in range(len(mesh_data.vertices)):
+                    try:
+                        weight = vertex_group.weight(vertex_index)
+                    except RuntimeError:
+                        continue
+                    if weight == 0.0:
+                        continue
+                    w = Psk.Weight()
+                    w.bone_index = bone_index
+                    w.point_index = vertex_offset + vertex_index
+                    w.weight = weight
+                    psk.weights.append(w)
+                    vertices_assigned_weights[vertex_index] = True
+
+            # Assign vertices that have not been assigned weights to the root bone of the armature.
+            fallback_weight_bone_index = psx_bone_create_result.armature_object_root_bone_indices[armature_object]
+            for vertex_index, assigned in enumerate(vertices_assigned_weights):
+                if not assigned:
+                    w = Psk.Weight()
+                    w.bone_index = fallback_weight_bone_index
+                    w.point_index = vertex_offset + vertex_index
+                    w.weight = 1.0
+                    psk.weights.append(w)
+
+        if evaluated_mesh_object is not None:
+            bpy.data.objects.remove(mesh_object)
+            del mesh_object
+
+        if evaluated_mesh_data is not None:
+            bpy.data.meshes.remove(mesh_data)
+            del mesh_data
+
+        context.window_manager.progress_update(object_index)
+
+    # Restore the original pose position of the armature objects.
+    for armature_object, pose_position in original_armature_object_pose_positions.items():
+        armature_data = typing_cast(Armature, armature_object.data)
+        armature_data.pose_position = pose_position
+
+    # https://github.com/DarklightGames/io_scene_psk_psa/issues/129.
+    psk.sort_and_normalize_weights()
+
+    context.window_manager.progress_end()
+
+    return PskBuildResult(psk, warnings)

io_scene_psk_psa/psk/export/operators.py

@@ -0,0 +1,516 @@
+from pathlib import Path
+from typing import Iterable, cast as typing_cast
+
+import bpy
+from bpy.props import StringProperty
+from bpy.types import Context, Depsgraph, Material, Object, Operator, Scene
+from bpy_extras.io_utils import ExportHelper
+
+from .properties import PSK_PG_export, PskExportMixin
+from ..builder import (
+    PskBuildOptions,
+    build_psk,
+    get_materials_for_mesh_objects,
+)
+from psk_psa_py.psk.writer import write_psk_to_path
+from ...shared.helpers import PsxBoneCollection, get_collection_export_operator_from_context, get_psk_input_objects_for_collection, populate_bone_collection_list, get_psk_input_objects_for_context
+from ...shared.ui import draw_bone_filter_mode
+from ...shared.operators import PSK_OT_bone_collection_list_populate, PSK_OT_bone_collection_list_select_all
+
+
+def populate_material_name_list(depsgraph: Depsgraph, mesh_objects: Iterable[Object], material_list):
+    materials = list(get_materials_for_mesh_objects(depsgraph, mesh_objects))
+
+    # Order the mesh object materials by the order any existing entries in the material list.
+    # This way, if the user has already set up the material list, we don't change the order.
+    material_names = [x.material_name for x in material_list]
+    materials = get_sorted_materials_by_names(materials, material_names)
+
+    material_list.clear()
+    for index, material in enumerate(materials):
+        m = material_list.add()
+        m.material_name = material.name if material is not None else 'None'
+        m.index = index
+
+
+class PSK_OT_populate_material_name_list(Operator):
+    bl_idname = 'psk.export_populate_material_name_list'
+    bl_label = 'Populate Material Name List'
+    bl_description = 'Populate the material name list from the objects that will be used in this export'
+    bl_options = {'INTERNAL'}
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        depsgraph = context.evaluated_depsgraph_get()
+        assert context.collection
+        input_objects = get_psk_input_objects_for_collection(context.collection)
+        try:
+            populate_material_name_list(depsgraph, [x.obj for x in input_objects.mesh_dfs_objects], export_operator.material_name_list)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+        return {'FINISHED'}
+
+
+
+def material_list_names_search_cb(self, context: Context, edit_text: str):
+    for material in bpy.data.materials:
+        yield material.name
+
+
+class PSK_OT_material_list_name_add(Operator):
+    bl_idname = 'psk.export_material_name_list_item_add'
+    bl_label = 'Add Material'
+    bl_description = 'Add a material to the material name list (useful if you want to add a material slot that is not actually used in the mesh)'
+    bl_options = {'INTERNAL'}
+
+    name: StringProperty(search=material_list_names_search_cb, name='Material Name', default='None')
+
+    def invoke(self, context, event):
+        assert context.window_manager
+        return context.window_manager.invoke_props_dialog(self)
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        m = export_operator.material_name_list.add()
+        m.material_name = self.name
+        m.index = len(export_operator.material_name_list) - 1
+        return {'FINISHED'}
+
+
+
+class PSK_OT_material_list_move_up(Operator):
+    bl_idname = 'psk.export_material_list_item_move_up'
+    bl_label = 'Move Up'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Move the selected material up one slot'
+
+    @classmethod
+    def poll(cls, context):
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+        return pg.material_name_list_index > 0
+
+    def execute(self, context):
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+        pg.material_name_list.move(pg.material_name_list_index, pg.material_name_list_index - 1)
+        pg.material_name_list_index -= 1
+        return {'FINISHED'}
+
+
+class PSK_OT_material_list_move_down(Operator):
+    bl_idname = 'psk.export_material_list_item_move_down'
+    bl_label = 'Move Down'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Move the selected material down one slot'
+
+    @classmethod
+    def poll(cls, context):
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+        return pg.material_name_list_index < len(pg.material_name_list) - 1
+
+    def execute(self, context):
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+        pg.material_name_list.move(pg.material_name_list_index, pg.material_name_list_index + 1)
+        pg.material_name_list_index += 1
+        return {'FINISHED'}
+
+
+class PSK_OT_material_list_name_move_up(Operator):
+    bl_idname = 'psk.export_material_name_list_item_move_up'
+    bl_label = 'Move Up'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Move the selected material name up one slot'
+
+    @classmethod
+    def poll(cls, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            return False
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        return export_operator.material_name_list_index > 0
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        export_operator.material_name_list.move(export_operator.material_name_list_index, export_operator.material_name_list_index - 1)
+        export_operator.material_name_list_index -= 1
+        return {'FINISHED'}
+
+
+class PSK_OT_material_list_name_move_down(Operator):
+    bl_idname = 'psk.export_material_name_list_item_move_down'
+    bl_label = 'Move Down'
+    bl_options = {'INTERNAL'}
+    bl_description = 'Move the selected material name down one slot'
+
+    @classmethod
+    def poll(cls, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            return False
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        return export_operator.material_name_list_index < len(export_operator.material_name_list) - 1
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PskExportMixin, export_operator)
+        export_operator.material_name_list.move(export_operator.material_name_list_index, export_operator.material_name_list_index + 1)
+        export_operator.material_name_list_index += 1
+        return {'FINISHED'}
+
+
+def get_sorted_materials_by_names(materials: Iterable[Material | None], material_names: list[str]) -> list[Material | None]:
+    """
+    Sorts the materials by the order of the material names list. Any materials not in the list will be appended to the
+    end of the list in the order they are found. None materials (representing empty material slots) are always
+    appended at the very end.
+
+    @param materials: A list of materials to sort (can include None)
+    @param material_names: A list of material names to sort by
+    @return: A sorted list of materials (with None at the end if present)
+    """
+    materials = list(materials)
+    has_none = None in materials
+    materials = [m for m in materials if m is not None]
+    
+    materials_in_collection = [m for m in materials if m.name in material_names]
+    materials_not_in_collection = [m for m in materials if m.name not in material_names]
+    materials_in_collection = sorted(materials_in_collection, key=lambda x: material_names.index(x.name))
+    
+    result: list[Material | None] = []
+    result.extend(materials_in_collection)
+    result.extend(materials_not_in_collection)
+    
+    if has_none:
+        result.append(None)
+    
+    return result
+
+
+def get_psk_build_options_from_property_group(scene: Scene, pg: PskExportMixin) -> PskBuildOptions:
+    options = PskBuildOptions()
+    options.object_eval_state = pg.object_eval_state
+    options.export_space = pg.export_space
+    options.bone_filter_mode = pg.bone_filter_mode
+    options.bone_collection_indices = [PsxBoneCollection(x.armature_object_name, x.armature_data_name, x.index) for x in pg.bone_collection_list if x.is_selected]
+    options.material_order_mode = pg.material_order_mode
+    options.material_name_list = [x.material_name for x in pg.material_name_list]
+    
+    match pg.transform_source:
+        case 'SCENE':
+            transform_source = getattr(scene, 'psx_export')
+        case 'CUSTOM':
+            transform_source = pg
+        case _:
+            assert False, f'Invalid transform source: {pg.transform_source}'
+    
+    options.scale = transform_source.scale
+    options.forward_axis = transform_source.forward_axis
+    options.up_axis = transform_source.up_axis
+
+    return options
+
+
+class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
+    bl_idname = 'psk.export_collection'
+    bl_label = 'Export'
+    bl_options = {'INTERNAL'}
+    filename_ext = '.psk'
+    filter_glob: StringProperty(default='*.psk', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for exporting the PSK file',
+        maxlen=1024,
+        default='',
+        subtype='FILE_PATH')
+    collection: StringProperty(options={'HIDDEN'})
+
+    def execute(self, context):
+        collection = bpy.data.collections.get(self.collection, None)
+
+        assert collection is not None
+        assert context.scene is not None
+
+        try:
+            input_objects = get_psk_input_objects_for_collection(collection)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        options = get_psk_build_options_from_property_group(context.scene, self)
+        filepath = str(Path(self.filepath).resolve())
+
+        try:
+            result = build_psk(context, input_objects, options)
+            for warning in result.warnings:
+                self.report({'WARNING'}, warning)
+            write_psk_to_path(result.psk, filepath)
+            if len(result.warnings) > 0:
+                self.report({'WARNING'}, f'PSK export successful with {len(result.warnings)} warnings')
+            else:
+                self.report({'INFO'}, f'PSK export successful')
+        except IOError as e:
+            self.report({'ERROR'}, f'Failed to write PSK file ({filepath}): {e}')
+            return {'CANCELLED'}
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        return {'FINISHED'}
+
+    def draw(self, context: Context):
+        layout = self.layout
+
+        assert layout is not None
+
+        flow = layout.grid_flow(row_major=True)
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+
+        # Mesh
+        mesh_header, mesh_panel = layout.panel('Mesh', default_closed=False)
+        mesh_header.label(text='Mesh', icon='MESH_DATA')
+        if mesh_panel:
+            flow = mesh_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(self, 'object_eval_state', text='Data')
+
+        # Bones
+        bones_header, bones_panel = layout.panel('Bones', default_closed=False)
+        bones_header.label(text='Bones', icon='BONE_DATA')
+        if bones_panel:
+            draw_bone_filter_mode(bones_panel, self, True)
+
+            if self.bone_filter_mode == 'BONE_COLLECTIONS':
+                row = bones_panel.row()
+                rows = max(3, min(len(self.bone_collection_list), 10))
+                row.template_list('PSX_UL_bone_collection_list', '', self, 'bone_collection_list', self, 'bone_collection_list_index', rows=rows)
+                col = row.column(align=True)
+                col.operator(PSK_OT_bone_collection_list_populate.bl_idname, text='', icon='FILE_REFRESH')
+                col.separator()
+                op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_HLT')
+                op.is_selected = True
+                op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_DEHLT')
+                op.is_selected = False
+
+        # Materials
+        materials_header, materials_panel = layout.panel('Materials', default_closed=False)
+        materials_header.label(text='Materials', icon='MATERIAL')
+
+        if materials_panel:
+            flow = materials_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(self, 'material_order_mode', text='Material Order')
+
+            if self.material_order_mode == 'MANUAL':
+                rows = max(3, min(len(self.material_name_list), 10))
+                row = materials_panel.row()
+                row.template_list('PSK_UL_material_names', '', self, 'material_name_list', self, 'material_name_list_index', rows=rows)
+                col = row.column(align=True)
+                col.operator(PSK_OT_populate_material_name_list.bl_idname, text='', icon='FILE_REFRESH')
+                col.separator()
+                col.operator(PSK_OT_material_list_name_move_up.bl_idname, text='', icon='TRIA_UP')
+                col.operator(PSK_OT_material_list_name_move_down.bl_idname, text='', icon='TRIA_DOWN')
+                col.separator()
+                col.operator(PSK_OT_material_list_name_add.bl_idname, text='', icon='ADD')
+
+        # Transform
+        transform_header, transform_panel = layout.panel('Transform', default_closed=False)
+        transform_header.label(text='Transform')
+        if transform_panel:
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(self, 'export_space')
+            flow.prop(self, 'transform_source')
+
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+
+            match self.transform_source:
+                case 'SCENE':
+                    transform_source = getattr(context.scene, 'psx_export')
+                    flow.enabled = False
+                case 'CUSTOM':
+                    transform_source = self
+                case _:
+                    assert False, f'Invalid transform source: {self.transform_source}'
+        
+            flow.prop(transform_source, 'scale')
+            flow.prop(transform_source, 'forward_axis')
+            flow.prop(transform_source, 'up_axis')
+
+
+class PSK_OT_export(Operator, ExportHelper):
+    bl_idname = 'psk.export'
+    bl_label = 'Export'
+    bl_options = {'INTERNAL', 'UNDO'}
+    bl_description = 'Export selected meshes to PSK'
+    filename_ext = '.psk'
+    filter_glob: StringProperty(default='*.psk', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for exporting the PSK file',
+        maxlen=1024,
+        default='')
+
+    def invoke(self, context, event):
+        try:
+            input_objects = get_psk_input_objects_for_context(context)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+
+        populate_bone_collection_list(pg.bone_collection_list, input_objects.armature_objects)
+
+        depsgraph = context.evaluated_depsgraph_get()
+
+        try:
+            populate_material_name_list(depsgraph, [x.obj for x in input_objects.mesh_dfs_objects], pg.material_name_list)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        assert context.window_manager
+        context.window_manager.fileselect_add(self)
+
+        return {'RUNNING_MODAL'}
+
+    def draw(self, context):
+        layout = self.layout
+
+        assert layout
+
+        pg = typing_cast(PSK_PG_export, getattr(context.scene, 'psk_export'))
+
+        # Mesh
+        mesh_header, mesh_panel = layout.panel('Mesh', default_closed=False)
+        mesh_header.label(text='Mesh', icon='MESH_DATA')
+        if mesh_panel:
+            flow = mesh_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'object_eval_state', text='Data')
+
+        # Bones
+        bones_header, bones_panel = layout.panel('Bones', default_closed=False)
+        bones_header.label(text='Bones', icon='BONE_DATA')
+        if bones_panel:
+            draw_bone_filter_mode(bones_panel, pg)
+            if pg.bone_filter_mode == 'BONE_COLLECTIONS':
+                row = bones_panel.row()
+                rows = max(3, min(len(pg.bone_collection_list), 10))
+                row.template_list('PSX_UL_bone_collection_list', '', pg, 'bone_collection_list', pg, 'bone_collection_list_index', rows=rows)
+
+        # Materials
+        materials_header, materials_panel = layout.panel('Materials', default_closed=False)
+        materials_header.label(text='Materials', icon='MATERIAL')
+        if materials_panel:
+            flow = materials_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'material_order_mode', text='Material Order')
+
+            if pg.material_order_mode == 'MANUAL':
+                row = materials_panel.row()
+                rows = max(3, min(len(pg.bone_collection_list), 10))
+                row.template_list('PSK_UL_material_names', '', pg, 'material_name_list', pg, 'material_name_list_index', rows=rows)
+                col = row.column(align=True)
+                col.operator(PSK_OT_material_list_move_up.bl_idname, text='', icon='TRIA_UP')
+                col.operator(PSK_OT_material_list_move_down.bl_idname, text='', icon='TRIA_DOWN')
+
+        # Transform
+        transform_header, transform_panel = layout.panel('Transform', default_closed=False)
+        transform_header.label(text='Transform')
+        if transform_panel:
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'export_space')
+            flow.prop(pg, 'transform_source')
+
+            flow = transform_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+
+            match pg.transform_source:
+                case 'SCENE':
+                    transform_source = getattr(context.scene, 'psx_export')
+                    flow.enabled = False
+                case 'CUSTOM':
+                    transform_source = pg
+                case _:
+                    assert False, f'Invalid transform source: {pg.transform_source}'
+        
+            flow.prop(transform_source, 'scale')
+            flow.prop(transform_source, 'forward_axis')
+            flow.prop(transform_source, 'up_axis')
+        
+        # Extended Format
+        extended_format_header, extended_format_panel = layout.panel('Extended Format', default_closed=False)
+        extended_format_header.label(text='Extended Format')
+        if extended_format_panel:
+            flow = extended_format_panel.grid_flow(row_major=True)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(pg, 'should_export_vertex_normals', text='Vertex Normals')
+
+    def execute(self, context):
+        pg = getattr(context.scene, 'psk_export')
+
+        assert context.scene
+
+        input_objects = get_psk_input_objects_for_context(context)
+        options = get_psk_build_options_from_property_group(context.scene, pg)
+
+        try:
+            result = build_psk(context, input_objects, options)
+            for warning in result.warnings:
+                self.report({'WARNING'}, warning)
+            write_psk_to_path(result.psk, self.filepath)
+            if len(result.warnings) > 0:
+                self.report({'WARNING'}, f'PSK export successful with {len(result.warnings)} warnings')
+            else:
+                self.report({'INFO'}, f'PSK export successful')
+        except IOError as e:
+            self.report({'ERROR'}, f'Failed to write PSK file ({self.filepath}): {e}')
+            return {'CANCELLED'}
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+
+        return {'FINISHED'}
+
+
+_classes = (
+    PSK_OT_material_list_move_up,
+    PSK_OT_material_list_move_down,
+    PSK_OT_export,
+    PSK_OT_export_collection,
+    PSK_OT_populate_material_name_list,
+    PSK_OT_material_list_name_move_up,
+    PSK_OT_material_list_name_move_down,
+    PSK_OT_material_list_name_add,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psk/export/properties.py

@@ -0,0 +1,60 @@
+from bpy.props import (
+    BoolProperty,
+    CollectionProperty,
+    EnumProperty,
+    IntProperty,
+    StringProperty,
+)
+from bpy.types import PropertyGroup
+
+from ...shared.types import ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin
+
+object_eval_state_items = (
+    ('EVALUATED', 'Evaluated', 'Use data from fully evaluated object'),
+    ('ORIGINAL', 'Original', 'Use data from original object with no modifiers applied'),
+)
+
+material_order_mode_items = (
+    ('AUTOMATIC', 'Automatic', 'Automatically order the materials'),
+    ('MANUAL', 'Manual', 'Manually arrange the materials'),
+)
+
+
+class PSK_PG_material_name_list_item(PropertyGroup):
+    material_name: StringProperty()
+    index: IntProperty()
+
+
+class PskExportMixin(ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin):
+    object_eval_state: EnumProperty(
+        items=object_eval_state_items,
+        name='Object Evaluation State',
+        default='EVALUATED'
+    )
+    material_order_mode: EnumProperty(
+        name='Material Order',
+        description='The order in which to export the materials',
+        items=material_order_mode_items,
+        default='AUTOMATIC'
+    )
+    material_name_list: CollectionProperty(type=PSK_PG_material_name_list_item)
+    material_name_list_index: IntProperty(default=0)
+    should_export_vertex_normals: BoolProperty(
+        name='Export Vertex Normals',
+        default=False,
+        description='Export VTXNORMS section.'
+    )
+
+
+class PSK_PG_export(PropertyGroup, PskExportMixin):
+    pass
+
+
+_classes = (
+    PSK_PG_material_name_list_item,
+    PSK_PG_export,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/psk/export/properties.pyi

@@ -0,0 +1,18 @@
+from ...shared.types import BpyCollectionProperty, ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin
+
+
+class PSK_PG_material_name_list_item:
+    material_name: str
+    index: int
+
+
+class PskExportMixin(ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin):
+    object_eval_state: str
+    material_order_mode: str
+    material_name_list: BpyCollectionProperty[PSK_PG_material_name_list_item]
+    material_name_list_index: int
+    should_export_vertex_normals: bool
+
+
+class PSK_PG_export(PskExportMixin):
+    pass

io_scene_psk_psa/psk/export/ui.py

@@ -0,0 +1,48 @@
+import bpy
+from bpy.types import UIList
+from typing import cast as typing_cast
+
+from .properties import PSK_PG_material_name_list_item
+
+
+class PSK_UL_material_names(UIList):
+    def draw_item(
+        self,
+        context,
+        layout,
+        data,
+        item,
+        icon,
+        active_data,
+        active_property,
+        index,
+        flt_flag
+    ):
+        row = layout.row()
+        item = typing_cast(PSK_PG_material_name_list_item, item)
+        material = bpy.data.materials.get(item.material_name, None)
+
+        # If the material is not found by name and the name is not 'None', show a not found icon
+        if item.material_name == 'None':
+            icon = 'NODE_MATERIAL'
+        else:
+            icon = 'NOT_FOUND' if material is None else 'NONE'
+
+        row.prop(item, 'material_name', text='', emboss=False,
+                 icon_value=layout.icon(material) if material else 0,
+                 icon=icon)
+
+        # Add right-aligned "Not Found" label if material is not found
+        if item.material_name != 'None' and material is None:
+            label_row = row.row()
+            label_row.alignment = 'RIGHT'
+            label_row.enabled = False
+            label_row.label(text='Not Found')
+
+
+_classes = (
+    PSK_UL_material_names,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psk/import_/operators.py

@@ -0,0 +1,185 @@
+import os
+from pathlib import Path
+
+from bpy.props import CollectionProperty, StringProperty
+from bpy.types import Context, FileHandler, Operator, OperatorFileListElement, UILayout
+from bpy_extras.io_utils import ImportHelper
+
+from ..importer import PskImportOptions, import_psk
+from ..properties import PskImportMixin
+from psk_psa_py.psk.reader import read_psk_from_file
+
+
+def get_psk_import_options_from_properties(property_group: PskImportMixin):
+    options = PskImportOptions()
+    options.should_import_mesh = property_group.should_import_mesh
+    options.should_import_extra_uvs = property_group.should_import_extra_uvs
+    options.should_import_vertex_colors = property_group.should_import_vertex_colors
+    options.should_import_vertex_normals = property_group.should_import_vertex_normals
+    options.vertex_color_space = property_group.vertex_color_space
+    options.should_import_armature = property_group.should_import_armature
+    options.bone_length = property_group.bone_length
+    options.should_import_materials = property_group.should_import_materials
+    options.should_import_shape_keys = property_group.should_import_shape_keys
+    options.scale = property_group.scale
+
+    if property_group.bdk_repository_id:
+        options.bdk_repository_id = property_group.bdk_repository_id
+
+    return options
+
+
+def psk_import_draw(layout: UILayout, props: PskImportMixin):
+    row = layout.row()
+
+    col = row.column()
+    col.use_property_split = True
+    col.use_property_decorate = False
+    col.prop(props, 'components')
+
+    if props.should_import_mesh:
+        mesh_header, mesh_panel = layout.panel('mesh_panel_id', default_closed=False)
+        mesh_header.label(text='Mesh', icon='MESH_DATA')
+
+        if mesh_panel:
+            row = mesh_panel.row()
+            col = row.column()
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(props, 'should_import_extra_uvs', text='Extra UVs')
+            col.prop(props, 'should_import_materials', text='Materials')
+            col.prop(props, 'should_import_vertex_colors', text='Vertex Colors')
+            if props.should_import_vertex_colors:
+                col.prop(props, 'vertex_color_space')
+            col.separator()
+            col.prop(props, 'should_import_vertex_normals', text='Vertex Normals')
+            col.prop(props, 'should_import_shape_keys', text='Shape Keys')
+
+    if props.should_import_armature:
+        armature_header, armature_panel = layout.panel('armature_panel_id', default_closed=False)
+        armature_header.label(text='Armature', icon='OUTLINER_DATA_ARMATURE')
+
+        if armature_panel:
+            row = armature_panel.row()
+            col = row.column()
+            col.use_property_split = True
+            col.use_property_decorate = False
+            col.prop(props, 'bone_length')
+
+    transform_header, transform_panel = layout.panel('transform_panel_id', default_closed=False)
+    transform_header.label(text='Transform')
+    if transform_panel:
+        row = transform_panel.row()
+        col = row.column()
+        col.use_property_split = True
+        col.use_property_decorate = False
+        col.prop(props, 'scale')
+
+
+class PSK_OT_import(Operator, ImportHelper, PskImportMixin):
+    bl_idname = 'psk.import_file'
+    bl_label = 'Import'
+    bl_options = {'INTERNAL', 'UNDO', 'PRESET'}
+    bl_description = 'Import a PSK file'
+    filename_ext = '.psk'
+    filter_glob: StringProperty(default='*.psk;*.pskx', options={'HIDDEN'})
+    filepath: StringProperty(
+        name='File Path',
+        description='File path used for exporting the PSK file',
+        maxlen=1024,
+        default='')
+
+    def execute(self, context):
+        try:
+            psk = read_psk_from_file(self.filepath)
+        except OSError as e:
+            self.report({'ERROR'}, f'Failed to read "{self.filepath}". The file may be corrupted or not a valid PSK file: {e}')
+            return {'CANCELLED'}
+
+        name = os.path.splitext(os.path.basename(self.filepath))[0]
+        options = get_psk_import_options_from_properties(self)
+        result = import_psk(psk, context, name, options)
+
+        if len(result.warnings):
+            message = f'PSK imported as "{result.root_object.name}" with {len(result.warnings)} warning(s)\n'
+            message += '\n'.join(result.warnings)
+            self.report({'WARNING'}, message)
+        else:
+            self.report({'INFO'}, f'PSK imported as "{result.root_object.name}"')
+
+        return {'FINISHED'}
+
+    def draw(self, context):
+        assert self.layout
+        psk_import_draw(self.layout, self)
+
+
+class PSK_OT_import_drag_and_drop(Operator, PskImportMixin):
+    bl_idname = 'psk.import_drag_and_drop'
+    bl_label = 'Import PSK'
+    bl_options = {'INTERNAL', 'UNDO', 'PRESET'}
+    bl_description = 'Import PSK files by dragging and dropping them onto the 3D view'
+
+    directory: StringProperty(subtype='FILE_PATH', options={'SKIP_SAVE', 'HIDDEN'})
+    files: CollectionProperty(type=OperatorFileListElement, options={'SKIP_SAVE', 'HIDDEN'})
+
+    @classmethod
+    def poll(cls, context) -> bool:
+        return context.area is not None and context.area.type == 'VIEW_3D'
+
+    def draw(self, context):
+        assert self.layout
+        psk_import_draw(self.layout, self)
+
+    def invoke(self, context, event):
+        assert context.window_manager
+        context.window_manager.invoke_props_dialog(self)
+        return {'RUNNING_MODAL'}
+
+    def execute(self, context):
+        warning_count = 0
+
+        options = get_psk_import_options_from_properties(self)
+
+        for file in self.files:
+            filepath = Path(self.directory) / file.name
+            try:
+                psk = read_psk_from_file(filepath)
+            except OSError as e:
+                self.report({'ERROR'}, f'Failed to read "{filepath}". The file may be corrupted or not a valid PSK file: {e}')
+                return {'CANCELLED'}
+
+            name = os.path.splitext(file.name)[0]
+            result = import_psk(psk, context, name, options)
+            if result.warnings:
+                warning_count += len(result.warnings)
+
+        if warning_count > 0:
+            self.report({'WARNING'}, f'Imported {len(self.files)} PSK file(s) with {warning_count} warning(s)')
+        else:
+            self.report({'INFO'}, f'Imported {len(self.files)} PSK file(s)')
+
+        return {'FINISHED'}
+
+
+# TODO: move to another file
+class PSK_FH_file_handler(FileHandler):
+    bl_idname = 'PSK_FH_import'
+    bl_label = 'Unreal PSK'
+    bl_import_operator = PSK_OT_import_drag_and_drop.bl_idname
+    bl_export_operator = 'psk.export_collection'
+    bl_file_extensions = '.psk;.pskx'
+
+    @classmethod
+    def poll_drop(cls, context: Context) -> bool:
+        return context.area is not None and context.area.type == 'VIEW_3D'
+
+
+_classes = (
+    PSK_OT_import,
+    PSK_OT_import_drag_and_drop,
+    PSK_FH_file_handler,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/psk/importer.py

@@ -0,0 +1,309 @@
+import bmesh
+import bpy
+import numpy as np
+
+from bpy.types import Context, Object, VertexGroup, ArmatureModifier, FloatColorAttribute
+from mathutils import Matrix, Quaternion, Vector
+from typing import cast as typing_cast
+
+from psk_psa_py.psk.data import Psk
+from psk_psa_py.shared.data import PsxBone
+from .properties import poly_flags_to_triangle_type_and_bit_flags
+from ..shared.helpers import is_bdk_addon_loaded, rgb_to_srgb
+
+
+class PskImportOptions:
+    def __init__(self):
+        self.should_import_mesh = True
+        self.should_reuse_materials = True
+        self.should_import_vertex_colors = True
+        self.vertex_color_space = 'SRGB'
+        self.should_import_vertex_normals = True
+        self.should_import_extra_uvs = True
+        self.should_import_armature = True
+        self.should_import_shape_keys = True
+        self.bone_length = 1.0
+        self.should_import_materials = True
+        self.scale = 1.0
+        self.bdk_repository_id: str | None = None
+
+
+class ImportBone:
+    """
+    Intermediate bone type for the purpose of construction.
+    """
+    def __init__(self, index: int, psk_bone: PsxBone):
+        self.index: int = index
+        self.psk_bone: PsxBone = psk_bone
+        self.parent: ImportBone | None = None
+        self.local_rotation: Quaternion = Quaternion()
+        self.local_translation: Vector = Vector()
+        self.world_rotation_matrix: Matrix = Matrix()
+        self.world_matrix: Matrix = Matrix()
+        self.original_rotation: Quaternion = Quaternion()
+        self.original_location: Vector = Vector()
+        self.post_rotation: Quaternion = Quaternion()
+
+
+class PskImportResult:
+    def __init__(self):
+        self.warnings: list[str] = []
+        self.armature_object: Object | None = None
+        self.mesh_object: Object | None = None
+
+    @property
+    def root_object(self) -> Object:
+        return self.armature_object if self.armature_object is not None else self.mesh_object
+
+
+def import_psk(psk: Psk, context: Context, name: str, options: PskImportOptions) -> PskImportResult:
+    result = PskImportResult()
+    armature_object = None
+    mesh_object = None
+
+    assert context.scene
+    assert bpy.context.view_layer
+
+    if options.should_import_armature:
+        # Armature
+        armature_data = bpy.data.armatures.new(name)
+        armature_object = bpy.data.objects.new(name, armature_data)
+        armature_object.show_in_front = True
+
+        context.scene.collection.objects.link(armature_object)
+
+        try:
+            bpy.ops.object.mode_set(mode='OBJECT')
+        except:
+            pass
+
+        armature_object.select_set(state=True)
+        bpy.context.view_layer.objects.active = armature_object
+
+        bpy.ops.object.mode_set(mode='EDIT')
+
+        import_bones: list[ImportBone] = []
+
+        for bone_index, psk_bone in enumerate(psk.bones):
+            import_bone = ImportBone(bone_index, psk_bone)
+            psk_bone.parent_index = max(0, psk_bone.parent_index)
+            import_bone.local_rotation = Quaternion(tuple(psk_bone.rotation))
+            import_bone.local_translation = Vector(tuple(psk_bone.location))
+            if psk_bone.parent_index == 0 and bone_index == 0:
+                import_bone.world_rotation_matrix = import_bone.local_rotation.to_matrix()
+                import_bone.world_matrix = Matrix.Translation(import_bone.local_translation)
+            import_bones.append(import_bone)
+
+        for bone_index, bone in enumerate(import_bones):
+            if bone.psk_bone.parent_index == 0 and bone_index == 0:
+                continue
+            parent = import_bones[bone.psk_bone.parent_index]
+            bone.parent = parent
+            bone.world_matrix = parent.world_rotation_matrix.to_4x4()
+            translation = bone.local_translation.copy()
+            translation.rotate(parent.world_rotation_matrix)
+            bone.world_matrix.translation = parent.world_matrix.translation + translation
+            bone.world_rotation_matrix = bone.local_rotation.conjugated().to_matrix()
+            bone.world_rotation_matrix.rotate(parent.world_rotation_matrix)
+
+        # Create all the bones up-front.
+        # This allows us to set up the parent-child relationships properly even if the parent bone comes after the child bone in the PSK file.
+        for import_bone in import_bones:
+            bone_name = import_bone.psk_bone.name.decode('utf-8')
+            edit_bone = armature_data.edit_bones.new(bone_name)
+
+        for import_bone in import_bones:
+            bone_name = import_bone.psk_bone.name.decode('utf-8')
+            edit_bone = armature_data.edit_bones[bone_name]
+
+            if import_bone.parent is not None:
+                edit_bone.parent = armature_data.edit_bones[import_bone.psk_bone.parent_index]
+            else:
+                import_bone.local_rotation.conjugate()
+
+            edit_bone.tail = Vector((0.0, options.bone_length, 0.0))
+            edit_bone_matrix = import_bone.local_rotation.conjugated()
+            edit_bone_matrix.rotate(import_bone.world_matrix)
+            edit_bone_matrix = edit_bone_matrix.to_matrix().to_4x4()
+            edit_bone_matrix.translation = import_bone.world_matrix.translation
+            edit_bone.matrix = edit_bone_matrix
+
+    # Mesh
+    if options.should_import_mesh:
+        mesh_data = bpy.data.meshes.new(name)
+        mesh_object = bpy.data.objects.new(name, mesh_data)
+
+        # Materials
+        if options.should_import_materials:
+            for material_index, psk_material in enumerate(psk.materials):
+                material_name = psk_material.name.decode('utf-8')
+                material = None
+
+                if options.should_reuse_materials and material_name in bpy.data.materials:
+                    # Material already exists, just re-use it.
+                    material = bpy.data.materials[material_name]
+                elif is_bdk_addon_loaded() and psk.has_material_references:
+                    # Material does not yet exist, and we have the BDK addon installed.
+                    # Attempt to load it using BDK addon's operator.
+                    material_reference = psk.material_references[material_index]
+                    repository_id = options.bdk_repository_id if options.bdk_repository_id is not None else ''
+                    if material_reference and bpy.ops.bdk.link_material(reference=material_reference, repository_id=repository_id) == {'FINISHED'}:
+                        material = bpy.data.materials[material_name]
+                
+                if material is None:
+                    # Material was unable to be loaded, so just create a blank material.
+                    material = bpy.data.materials.new(material_name)
+                    mesh_triangle_type, mesh_triangle_bit_flags = poly_flags_to_triangle_type_and_bit_flags(psk_material.poly_flags)
+                    material.psk.mesh_triangle_type = mesh_triangle_type
+                    material.psk.mesh_triangle_bit_flags = mesh_triangle_bit_flags
+                
+                mesh_data.materials.append(material)
+
+        bm = bmesh.new()
+
+        # Vertices
+        for point in psk.points:
+            bm.verts.new(tuple(point))
+
+        bm.verts.ensure_lookup_table()
+
+        # Faces
+        invalid_face_indices = set()
+        for face_index, face in enumerate(psk.faces):
+            points = (
+                bm.verts[psk.wedges[face.wedge_indices[2]].point_index],
+                bm.verts[psk.wedges[face.wedge_indices[1]].point_index],
+                bm.verts[psk.wedges[face.wedge_indices[0]].point_index],
+            )
+            try:
+                bm_face = bm.faces.new(points)
+                bm_face.material_index = face.material_index
+            except ValueError:
+                # This happens for two reasons:
+                # 1. Two or more of the face's points are the same. (i.e, point indices of [0, 0, 1])
+                # 2. The face is a duplicate of another face. (i.e., point indices of [0, 1, 2] and [0, 1, 2])
+                invalid_face_indices.add(face_index)
+
+        # TODO: Handle invalid faces better.
+        if len(invalid_face_indices) > 0:
+            result.warnings.append(f'Discarded {len(invalid_face_indices)} invalid face(s).')
+
+        face_count = len(bm.faces)
+
+        bm.to_mesh(mesh_data)
+
+        # Texture Coordinates
+        uv_layer_data_index = 0
+        uv_layer_data = np.zeros((face_count * 3, 2), dtype=np.float32)
+        for face_index, face in enumerate(psk.faces):
+            if face_index in invalid_face_indices:
+                continue
+            for wedge in map(lambda i: psk.wedges[i], reversed(face.wedge_indices)):
+                uv_layer_data[uv_layer_data_index] = wedge.u, 1.0 - wedge.v
+                uv_layer_data_index += 1
+        uv_layer = mesh_data.uv_layers.new(name='UVMap')
+        uv_layer.uv.foreach_set('vector', uv_layer_data.ravel())
+
+        # Extra UVs
+        if psk.has_extra_uvs and options.should_import_extra_uvs:
+            for extra_uv_index, extra_uvs in enumerate(psk.extra_uvs):
+                uv_layer_data = np.zeros((face_count * 3, 2), dtype=np.float32)
+                uv_layer_data_index = 0
+                for face_index, face in enumerate(psk.faces):
+                    if face_index in invalid_face_indices:
+                        continue
+                    for wedge_index in reversed(face.wedge_indices):
+                        u, v = extra_uvs[wedge_index]
+                        uv_layer_data[uv_layer_data_index] = u, 1.0 - v
+                        uv_layer_data_index += 1
+                uv_layer = mesh_data.uv_layers.new(name=f'EXTRAUV{extra_uv_index}')
+                uv_layer.uv.foreach_set('vector', uv_layer_data.ravel())
+
+        # Vertex Colors
+        if psk.has_vertex_colors and options.should_import_vertex_colors:
+            psk_vertex_colors = np.zeros((len(psk.vertex_colors), 4))
+            for vertex_color_index in range(len(psk.vertex_colors)):
+                psk_vertex_colors[vertex_color_index] = tuple(psk.vertex_colors[vertex_color_index])
+            psk_vertex_colors /= 255.0
+
+            # Convert vertex colors to sRGB if necessary.
+            if options.vertex_color_space == 'SRGBA':
+                psk_vertex_colors[:, :3] = np.vectorize(rgb_to_srgb)(psk_vertex_colors[:, :3])
+
+            # Map the PSK vertex colors to the face corners.
+            face_count = len(psk.faces) - len(invalid_face_indices)
+            face_corner_colors = np.full((face_count * 3, 4), 1.0)
+            face_corner_color_index = 0
+            for face_index, face in enumerate(psk.faces):
+                if face_index in invalid_face_indices:
+                    continue
+                for wedge_index in reversed(face.wedge_indices):
+                    face_corner_colors[face_corner_color_index] = psk_vertex_colors[wedge_index]
+                    face_corner_color_index += 1
+
+            # Create the vertex color attribute.
+            face_corner_color_attribute = mesh_data.attributes.new(name='VERTEXCOLOR', type='FLOAT_COLOR', domain='CORNER')
+            face_corner_color_attribute = typing_cast(FloatColorAttribute, face_corner_color_attribute)
+            face_corner_color_attribute.data.foreach_set('color', face_corner_colors.ravel())
+
+        # Vertex Normals
+        if psk.has_vertex_normals and options.should_import_vertex_normals:
+            mesh_data.polygons.foreach_set('use_smooth', [True] * len(mesh_data.polygons))
+            normals = []
+            for vertex_normal in psk.vertex_normals:
+                normals.append(tuple(vertex_normal))
+            mesh_data.normals_split_custom_set_from_vertices(normals)
+        else:
+            mesh_data.shade_smooth()
+
+        bm.normal_update()
+        bm.free()
+
+        # Weights
+        # Get a list of all bones that have weights associated with them.
+        vertex_group_bone_indices = set(map(lambda weight: weight.bone_index, psk.weights))
+        vertex_groups: list[VertexGroup | None] = [None] * len(psk.bones)
+        for bone_index, psk_bone in map(lambda x: (x, psk.bones[x]), vertex_group_bone_indices):
+            vertex_groups[bone_index] = mesh_object.vertex_groups.new(name=psk_bone.name.decode('windows-1252'))
+
+        for weight in psk.weights:
+            vertex_groups[weight.bone_index].add((weight.point_index,), weight.weight, 'ADD')
+
+        # Morphs (Shape Keys)
+        if options.should_import_shape_keys:
+            morph_data_iterator = iter(psk.morph_data)
+
+            if psk.has_morph_data:
+                mesh_object.shape_key_add(name='MORPH_BASE', from_mix=False)
+
+            for morph_info in psk.morph_infos:
+                shape_key = mesh_object.shape_key_add(name=morph_info.name.decode('windows-1252'), from_mix=False)
+                shape_key.value = 0.0
+
+                for _ in range(morph_info.vertex_count):
+                    morph_data = next(morph_data_iterator)
+                    x, y, z = morph_data.position_delta
+                    shape_key.data[morph_data.point_index].co += Vector((x, -y, z))
+
+        context.scene.collection.objects.link(mesh_object)
+
+        # Add armature modifier to our mesh object.
+        if options.should_import_armature:
+            armature_modifier = mesh_object.modifiers.new(name='Armature', type='ARMATURE')
+            armature_modifier = typing_cast(ArmatureModifier, armature_modifier)
+            armature_modifier.object = armature_object
+            mesh_object.parent = armature_object
+
+    root_object = armature_object if options.should_import_armature else mesh_object
+    assert root_object
+    root_object.scale = (options.scale, options.scale, options.scale)
+
+    try:
+        bpy.ops.object.mode_set(mode='OBJECT')
+    except:
+        pass
+
+    result.armature_object = armature_object
+    result.mesh_object = mesh_object
+
+    return result

io_scene_psk_psa/psk/properties.py

@@ -0,0 +1,154 @@
+import sys
+
+from bpy.props import BoolProperty, EnumProperty, FloatProperty, StringProperty
+from bpy.types import PropertyGroup
+
+mesh_triangle_types_items = (
+    ('NORMAL', 'Normal', 'Normal one-sided', 0),
+    ('NORMAL_TWO_SIDED', 'Normal Two-Sided', 'Normal but two-sided', 1),
+    ('TRANSLUCENT', 'Translucent', 'Translucent two-sided', 2),
+    ('MASKED', 'Masked', 'Masked two-sided', 3),
+    ('MODULATE', 'Modulate', 'Modulation blended two-sided', 4),
+    ('PLACEHOLDER', 'Placeholder', 'Placeholder triangle for positioning weapon. Invisible', 8),
+)
+
+mesh_triangle_bit_flags_items = (
+    ('UNLIT', 'Unlit', 'Full brightness, no lighting', 16),
+    ('FLAT', 'Flat', 'Flat surface, don\'t do bMeshCurvy thing', 32),
+    ('ENVIRONMENT', 'Environment', 'Environment mapped', 64),
+    ('NO_SMOOTH', 'No Smooth', 'No bilinear filtering on this poly\'s texture', 128),
+)
+
+class PSX_PG_material(PropertyGroup):
+    mesh_triangle_type: EnumProperty(
+        name='Triangle Type',
+        items=mesh_triangle_types_items
+        )
+    mesh_triangle_bit_flags: EnumProperty(
+        name='Triangle Bit Flags',
+        items=mesh_triangle_bit_flags_items,
+        options={'ENUM_FLAG'}
+        )
+
+mesh_triangle_types_items_dict = {item[0]: item[3] for item in mesh_triangle_types_items}
+mesh_triangle_bit_flags_items_dict = {item[0]: item[3] for item in mesh_triangle_bit_flags_items}
+
+
+def triangle_type_and_bit_flags_to_poly_flags(mesh_triangle_type: str, mesh_triangle_bit_flags: set[str]) -> int:
+    poly_flags = 0
+    poly_flags |= mesh_triangle_types_items_dict.get(mesh_triangle_type, 0)
+    for flag in mesh_triangle_bit_flags:
+        poly_flags |= mesh_triangle_bit_flags_items_dict.get(flag, 0)
+    return poly_flags
+
+
+def poly_flags_to_triangle_type_and_bit_flags(poly_flags: int) -> tuple[str, set[str]]:
+    try:
+        triangle_type = next(item[0] for item in mesh_triangle_types_items if item[3] == (poly_flags & 15))
+    except StopIteration:
+        triangle_type = 'NORMAL'
+    triangle_bit_flags = {item[0] for item in mesh_triangle_bit_flags_items if item[3] & poly_flags}
+    return triangle_type, triangle_bit_flags
+
+
+def should_import_mesh_get(self):
+    return self.components in {'ALL', 'MESH'}
+
+
+def should_import_skleton_get(self):
+    return self.components in {'ALL', 'ARMATURE'}
+
+
+vertex_color_space_items = (
+    ('LINEAR', 'Linear', ''),
+    ('SRGBA', 'sRGBA', ''),
+)
+
+psk_import_components_items = (
+    ('ALL', 'Mesh & Armature', 'Import mesh and armature'),
+    ('MESH', 'Mesh Only', 'Import mesh only'),
+    ('ARMATURE', 'Armature Only', 'Import armature only'),
+)
+
+class PskImportMixin:
+    should_import_vertex_colors: BoolProperty(
+        default=True,
+        options=set(),
+        name='Import Vertex Colors',
+        description='Import vertex colors, if available'
+    )
+    vertex_color_space: EnumProperty(
+        name='Vertex Color Space',
+        options=set(),
+        description='The source vertex color space',
+        default='SRGBA',
+        items=vertex_color_space_items
+    )
+    should_import_vertex_normals: BoolProperty(
+        default=True,
+        name='Import Vertex Normals',
+        options=set(),
+        description='Import vertex normals, if available.\n\nThis is only supported for PSKX files'
+    )
+    should_import_extra_uvs: BoolProperty(
+        default=True,
+        name='Import Extra UVs',
+        options=set(),
+        description='Import extra UV maps, if available'
+    )
+    components: EnumProperty(
+        name='Components',
+        options=set(),
+        description='Which components to import',
+        items=psk_import_components_items,
+        default='ALL'
+    )
+    should_import_mesh: BoolProperty(
+        name='Import Mesh',
+        get=should_import_mesh_get,
+    )
+    should_import_materials: BoolProperty(
+        default=True,
+        name='Import Materials',
+        options=set(),
+    )
+    should_import_armature: BoolProperty(
+        name='Import Skeleton',
+        get=should_import_skleton_get,
+    )
+    bone_length: FloatProperty(
+        default=1.0,
+        min=sys.float_info.epsilon,
+        step=100,
+        soft_min=1.0,
+        name='Bone Length',
+        options=set(),
+        subtype='DISTANCE',
+        description='Length of the bones'
+    )
+    should_import_shape_keys: BoolProperty(
+        default=True,
+        name='Import Shape Keys',
+        options=set(),
+        description='Import shape keys, if available.\n\nThis is only supported for PSKX files'
+    )
+    scale: FloatProperty(
+        name='Scale',
+        default=1.0,
+        soft_min=0.0,
+    )
+    bdk_repository_id: StringProperty(
+        name='BDK Repository ID',
+        default='',
+        options=set(),
+        description='The ID of the BDK repository to use for loading materials'
+    )
+
+
+_classes = (
+    PSX_PG_material,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/psk/properties.pyi

@@ -0,0 +1,23 @@
+class PSX_PG_material:
+    mesh_triangle_type: str
+    mesh_triangle_bit_flags: set[str]
+
+
+class PskImportMixin:
+    should_import_vertex_colors: bool
+    vertex_color_space: str
+    should_import_vertex_normals: bool
+    should_import_extra_uvs: bool
+    components: str
+    should_import_mesh: bool
+    should_import_materials: bool
+    should_import_armature: bool
+    bone_length: float
+    should_import_shape_keys: bool
+    scale: float
+    bdk_repository_id: str
+
+
+def triangle_type_and_bit_flags_to_poly_flags(mesh_triangle_type: str, mesh_triangle_bit_flags: set[str]) -> int: ...
+
+def poly_flags_to_triangle_type_and_bit_flags(poly_flags: int) -> tuple[str, set[str]]: ...

io_scene_psk_psa/psk/ui.py

@@ -0,0 +1,33 @@
+from bpy.types import Panel
+
+
+class PSK_PT_material(Panel):
+    bl_label = 'PSK Material'
+    bl_idname = 'PSK_PT_material'
+    bl_space_type = 'PROPERTIES'
+    bl_region_type = 'WINDOW'
+    bl_context = 'material'
+    bl_options = {'DEFAULT_CLOSED'}
+
+    @classmethod
+    def poll(cls, context):
+        return context.material is not None
+
+    def draw(self, context):
+        layout = self.layout
+        assert layout is not None
+        layout.use_property_split = True
+        layout.use_property_decorate = False
+        material = context.material
+        layout.prop(material.psk, 'mesh_triangle_type')
+        col = layout.column()
+        col.prop(material.psk, 'mesh_triangle_bit_flags', expand=True, text='Flags')
+
+
+_classes = (
+    PSK_PT_material,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

io_scene_psk_psa/shared/dfs.py

@@ -0,0 +1,148 @@
+"""
+Depth-first object iterator functions for Blender collections and view layers.
+
+These functions are used to iterate over objects in a collection or view layer in a depth-first manner, including
+instances. This is useful for exporters that need to traverse the object hierarchy in a predictable order.
+"""
+
+from typing import Iterable
+
+from bpy.types import Collection, Object, ViewLayer, LayerCollection
+from mathutils import Matrix
+
+
+class DfsObject:
+    """
+    Represents an object in a depth-first search.
+    """
+    def __init__(self, obj: Object, instance_objects: list[Object], matrix_world: Matrix):
+        self.obj = obj
+        self.instance_objects = instance_objects
+        self.matrix_world = matrix_world
+
+    @property
+    def is_visible(self) -> bool:
+        """
+        Check if the object is visible.
+
+        @return: True if the object is visible, False otherwise.
+        """
+        if self.instance_objects:
+            return self.instance_objects[-1].visible_get()
+        return self.obj.visible_get()
+
+    @property
+    def is_selected(self) -> bool:
+        """
+        Check if the object is selected.
+        @return: True if the object is selected, False otherwise.
+        """
+        if self.instance_objects:
+            return self.instance_objects[-1].select_get()
+        return self.obj.select_get()
+
+
+def _dfs_object_children(obj: Object, collection: Collection) -> Iterable[Object]:
+    """
+    Construct a list of objects in hierarchy order from `collection.objects`, only keeping those that are in the
+    collection.
+
+    @param obj: The object to start the search from.
+    @param collection:  The collection to search in.
+    @return: An iterable of objects in hierarchy order.
+    """
+    yield obj
+    for child in obj.children:
+        if child.name in collection.objects:
+            yield from _dfs_object_children(child, collection)
+
+
+def dfs_objects_in_collection(collection: Collection) -> Iterable[Object]:
+    """
+    Returns a depth-first iterator over all objects in a collection, only keeping those that are directly in the
+    collection.
+
+    @param collection: The collection to search in.
+    @return: An iterable of objects in hierarchy order.
+    """
+    objects_hierarchy = []
+    for obj in collection.objects:
+        if obj.parent is None or obj.parent not in set(collection.objects):
+            objects_hierarchy.append(obj)
+    for obj in objects_hierarchy:
+        yield from _dfs_object_children(obj, collection)
+
+
+def dfs_collection_objects(collection: Collection, visible_only: bool = False) -> Iterable[DfsObject]:
+    """
+    Depth-first search of objects in a collection, including recursing into instances.
+
+    @param collection: The collection to search in.
+    @return: An iterable of tuples containing the object, the instance objects, and the world matrix.
+    """
+    yield from _dfs_collection_objects_recursive(collection)
+
+
+def _dfs_collection_objects_recursive(
+        collection: Collection,
+        instance_objects: list[Object] | None = None,
+        matrix_world: Matrix = Matrix.Identity(4),
+        visited: set[Object] | None = None
+) -> Iterable[DfsObject]:
+    """
+    Depth-first search of objects in a collection, including recursing into instances.
+    This is a recursive function.
+
+    @param collection: The collection to search in.
+    @param instance_objects: The running hierarchy of instance objects.
+    @param matrix_world: The world matrix of the current object.
+    @param visited: A set of visited object-instance pairs.
+    @return: An iterable of tuples containing the object, the instance objects, and the world matrix.
+    """
+
+    # We want to also yield the top-level instance object so that callers can inspect the selection status etc.
+    if visited is None:
+        visited = set()
+
+    if instance_objects is None:
+        instance_objects = list()
+
+    # First, yield all objects in child collections.
+    for child in collection.children:
+        yield from _dfs_collection_objects_recursive(child, instance_objects, matrix_world.copy(), visited)
+
+    # Then, evaluate all objects in this collection.
+    for obj in dfs_objects_in_collection(collection):
+        visited_pair = (obj, instance_objects[-1] if instance_objects else None)
+        if visited_pair in visited:
+            continue
+        # If this an instance, we need to recurse into it.
+        if obj.instance_collection is not None:
+            # Calculate the instance transform.
+            instance_offset_matrix = Matrix.Translation(-obj.instance_collection.instance_offset)
+            # Recurse into the instance collection.
+            yield from _dfs_collection_objects_recursive(obj.instance_collection,
+                                                         instance_objects + [obj],
+                                                         matrix_world @ (obj.matrix_world @ instance_offset_matrix),
+                                                         visited)
+        else:
+            # Object is not an instance, yield it.
+            yield DfsObject(obj, instance_objects, matrix_world @ obj.matrix_world)
+            visited.add(visited_pair)
+
+
+def dfs_view_layer_objects(view_layer: ViewLayer) -> Iterable[DfsObject]:
+    """
+    Depth-first iterator over all objects in a view layer, including recursing into instances.
+
+    @param view_layer: The view layer to inspect.
+    @return: An iterable of tuples containing the object, the instance objects, and the world matrix.
+    """
+    visited = set()
+    def layer_collection_objects_recursive(layer_collection: LayerCollection):
+        for child in layer_collection.children:
+            yield from layer_collection_objects_recursive(child)
+        # Iterate only the top-level objects in this collection first.
+        yield from _dfs_collection_objects_recursive(layer_collection.collection, visited=visited)
+
+    yield from layer_collection_objects_recursive(view_layer.layer_collection)

io_scene_psk_psa/shared/helpers.py

@@ -0,0 +1,710 @@
+import bpy
+from collections import Counter
+from typing import Iterable, cast as typing_cast
+from bpy.types import Armature, AnimData, Collection, Context, Object, ArmatureModifier, SpaceProperties, PropertyGroup, Material
+from mathutils import Matrix, Vector, Quaternion as BpyQuaternion
+from psk_psa_py.shared.data import PsxBone, Quaternion, Vector3
+
+from ..shared.types import BpyCollectionProperty, PSX_PG_bone_collection_list_item
+
+
+def rgb_to_srgb(c: float) -> float:
+    if c > 0.0031308:
+        return 1.055 * (pow(c, (1.0 / 2.4))) - 0.055
+    return 12.92 * c
+
+
+def get_nla_strips_in_frame_range(animation_data: AnimData, frame_min: float, frame_max: float):
+    for nla_track in animation_data.nla_tracks:
+        if nla_track.mute:
+            continue
+        for strip in nla_track.strips:
+            if (strip.frame_start < frame_min and strip.frame_end > frame_max) or \
+                    (frame_min <= strip.frame_start < frame_max) or \
+                    (frame_min < strip.frame_end <= frame_max):
+                yield strip
+
+
+def populate_bone_collection_list(
+        bone_collection_list: BpyCollectionProperty[PSX_PG_bone_collection_list_item], 
+        armature_objects: Iterable[Object],
+        primary_key: str = 'OBJECT'
+        ):
+    """
+    Updates the bone collection list.
+
+    Selection is preserved between updates unless none of the groups were previously selected.
+    Otherwise, all collections are selected by default.
+
+    The primary key is used to determine how to group the armature objects. For example, if the primary key is
+    'DATA', then all bone collections with the same armature data-block will be under one entry.
+
+    :param bone_collection_list: The list to update.
+    :param armature_objects: The armature objects to populate the collection with.
+    :param primary_key: The primary key to use for the collection (one of 'OBJECT' or 'DATA').
+    :return: None
+    """
+    has_selected_collections = any([g.is_selected for g in bone_collection_list])
+    unassigned_collection_is_selected, selected_assigned_collection_names = True, []
+
+    if primary_key not in ('OBJECT', 'DATA'):
+        assert False, f'Invalid primary key: {primary_key}'
+
+    if not armature_objects:
+        return
+
+    if has_selected_collections:
+        # Preserve group selections before clearing the list.
+        # We handle selections for the unassigned group separately to cover the edge case
+        # where there might be an actual group with 'Unassigned' as its name.
+        unassigned_collection_idx, unassigned_collection_is_selected = next(iter([
+            (i, g.is_selected) for i, g in enumerate(bone_collection_list) if g.index == -1]), (-1, False))
+
+        selected_assigned_collection_names = [
+            g.name for i, g in enumerate(bone_collection_list) if i != unassigned_collection_idx and g.is_selected]
+
+
+    bone_collection_list.clear()
+
+    unique_armature_data = set()
+
+    for armature_object in armature_objects:
+        armature_data = typing_cast(Armature, armature_object.data)
+
+        if armature_data is None:
+            continue
+
+        if primary_key == 'DATA':
+            if armature_data in unique_armature_data:
+                # Skip this armature since we have already added an entry for it and we are using the data as the key.
+                continue
+            unique_armature_data.add(armature_data)
+        
+        unassigned_bone_count = sum(map(lambda bone: 1 if len(bone.collections) == 0 else 0, armature_data.bones))
+
+        if unassigned_bone_count > 0:
+            item = bone_collection_list.add()
+            item.armature_object_name = armature_object.name
+            item.armature_data_name = armature_data.name if armature_data else ''
+            item.name = 'Unassigned'
+            item.index = -1
+            # Count the number of bones without an assigned bone collection
+            item.count = unassigned_bone_count
+            item.is_selected = unassigned_collection_is_selected
+
+        for bone_collection_index, bone_collection in enumerate(armature_data.collections_all):
+            item = bone_collection_list.add()
+            item.armature_object_name = armature_object.name
+            item.armature_data_name = armature_data.name if armature_data else ''
+            item.name = bone_collection.name
+            item.index = bone_collection_index
+            item.count = len(bone_collection.bones)
+            item.is_selected = bone_collection.name in selected_assigned_collection_names if has_selected_collections else True
+
+
+def get_export_bone_names(armature_object: Object, bone_filter_mode: str, bone_collection_indices: Iterable[int]) -> list[str]:
+    """
+    Returns a sorted list of bone indices that should be exported for the given bone filter mode and bone collections.
+
+    Note that the ancestors of bones within the bone collections will also be present in the returned list.
+
+    :param armature_object: Blender object with type `'ARMATURE'`
+    :param bone_filter_mode: One of `['ALL', 'BONE_COLLECTIONS']`
+    :param bone_collection_indices: A list of bone collection indices to export.
+    :return: A sorted list of bone indices that should be exported.
+    """
+    if armature_object is None or armature_object.type != 'ARMATURE':
+        raise ValueError('An armature object must be supplied')
+
+    armature_data = typing_cast(Armature, armature_object.data)
+    bones = armature_data.bones
+    bone_names = [x.name for x in bones]
+
+    # Get a list of the bone indices that we are explicitly including.
+    bone_index_stack = []
+    is_exporting_unassigned_bone_collections = -1 in bone_collection_indices
+    bone_collections = list(armature_data.collections_all)
+
+    for bone_index, bone in enumerate(bones):
+        # Check if this bone is in any of the collections in the bone collection indices list.
+        this_bone_collection_indices = set(bone_collections.index(x) for x in bone.collections)
+        is_in_exported_bone_collections = len(set(bone_collection_indices).intersection(this_bone_collection_indices)) > 0
+
+        if bone_filter_mode == 'ALL' or \
+                (len(bone.collections) == 0 and is_exporting_unassigned_bone_collections) or \
+                is_in_exported_bone_collections:
+            bone_index_stack.append((bone_index, None))
+
+    # For each bone that is explicitly being added, recursively walk up the hierarchy and ensure that all of
+    # those ancestor bone indices are also in the list.
+    bone_indices = dict()
+    while len(bone_index_stack) > 0:
+        bone_index, instigator_bone_index = bone_index_stack.pop()
+        bone = bones[bone_index]
+        if bone.parent is not None:
+            parent_bone_index = bone_names.index(bone.parent.name)
+            if parent_bone_index not in bone_indices:
+                bone_index_stack.append((parent_bone_index, bone_index))
+        bone_indices[bone_index] = instigator_bone_index
+
+    # Sort the bone index list in-place.
+    bone_indices = [(x[0], x[1]) for x in bone_indices.items()]
+    bone_indices.sort(key=lambda x: x[0])
+
+    # Split out the bone indices and the instigator bone names into separate lists.
+    # We use the bone names for the return values because the bone name is a more universal way of referencing them.
+    # For example, users of this function may modify bone lists, which would invalidate the indices and require an
+    # index mapping scheme to resolve it. Using strings is more comfy and results in less code downstream.
+    bone_names = [bones[x[0]].name for x in bone_indices]
+
+    return bone_names
+
+
+def is_bdk_addon_loaded() -> bool:
+    return 'bdk' in dir(bpy.ops)
+
+
+def convert_string_to_cp1252_bytes(string: str) -> bytes:
+    try:
+        return bytes(string, encoding='windows-1252')
+    except UnicodeEncodeError as e:
+        raise RuntimeError(f'The string "{string}" contains characters that cannot be encoded in the Windows-1252 codepage') from e
+
+
+def create_psx_bones_from_blender_bones(
+        bones: list[bpy.types.Bone],
+        armature_object_matrix_world: Matrix,
+) -> list[PsxBone]:
+    """
+    Creates PSX bones from the given Blender bones.
+    
+    The bones are in world space based on the armature object's world matrix.
+    """
+    # Apply the scale of the armature object to the bone location.
+    _, _, armature_object_scale = armature_object_matrix_world.decompose()
+
+    psx_bones: list[PsxBone] = []
+    for bone in bones:
+        psx_bone = PsxBone()
+        psx_bone.name = convert_string_to_cp1252_bytes(bone.name)
+
+        if bone.parent is not None:
+            try:
+                parent_index = bones.index(bone.parent)
+                psx_bone.parent_index = parent_index
+                psx_bones[parent_index].children_count += 1
+            except ValueError:
+                pass
+
+        if bone.parent is not None:
+            # Child bone.
+            rotation = bone.matrix.to_quaternion().conjugated()
+            inverse_parent_rotation = bone.parent.matrix.to_quaternion().inverted()
+            parent_head = inverse_parent_rotation @ bone.parent.head
+            parent_tail = inverse_parent_rotation @ bone.parent.tail
+            location = (parent_tail - parent_head) + bone.head
+        else:
+            location = armature_object_matrix_world @ bone.head
+            bone_rotation = bone.matrix.to_quaternion().conjugated()
+            rotation = bone_rotation @ armature_object_matrix_world.to_3x3().to_quaternion()
+            rotation.conjugate()
+
+        location.x *= armature_object_scale.x
+        location.y *= armature_object_scale.y
+        location.z *= armature_object_scale.z
+
+        # Copy the calculated location and rotation to the bone.
+        psx_bone.location = convert_vector_to_vector3(location)
+        psx_bone.rotation = convert_bpy_quaternion_to_psx_quaternion(rotation)
+
+        psx_bones.append(psx_bone)
+
+    return psx_bones
+
+
+class PsxBoneResult:
+    def __init__(self, psx_bone: PsxBone, armature_object: Object | None) -> None:
+        self.psx_bone: PsxBone = psx_bone
+        self.armature_object: Object | None = armature_object
+
+
+class PsxBoneCreateResult:
+    def __init__(self,
+                 bones: list[PsxBoneResult],  # List of tuples of (psx_bone, armature_object)
+                 armature_object_root_bone_indices: dict[Object, int],
+                 armature_object_bone_names: dict[Object, list[str]],
+                 ):
+        self.bones = bones
+        self.armature_object_root_bone_indices = armature_object_root_bone_indices
+        self.armature_object_bone_names = armature_object_bone_names
+
+
+def convert_vector_to_vector3(vector: Vector) -> Vector3:
+    """
+    Convert a Blender mathutils.Vector to a psk_psa_py Vector3.
+    """
+    vector3 = Vector3()
+    vector3.x = vector.x
+    vector3.y = vector.y
+    vector3.z = vector.z
+    return vector3
+
+
+def convert_bpy_quaternion_to_psx_quaternion(quaternion: BpyQuaternion) -> Quaternion:
+    """
+    Convert a Blender mathutils.Quaternion to a psk_psa_py Quaternion.
+    """
+    psx_quaternion = Quaternion()
+    psx_quaternion.x = quaternion.x
+    psx_quaternion.y = quaternion.y
+    psx_quaternion.z = quaternion.z
+    psx_quaternion.w = quaternion.w
+    return psx_quaternion
+
+
+class PsxBoneCollection:
+    """
+    Stores the armature's object name, data-block name and bone collection index.
+    """
+    def __init__(self, armature_object_name: str, armature_data_name: str, index: int):
+        self.armature_object_name = armature_object_name
+        self.armature_data_name = armature_data_name
+        self.index = index
+
+
+class ObjectNode:
+    def __init__(self, obj: Object):
+        self.object = obj
+        self.parent: ObjectNode | None = None
+        self.children: list[ObjectNode] = []
+    
+    @property
+    def root(self):
+        """
+        Gets the root in the object hierarchy. This can return itself if this node has no parent.
+        """
+        n = self
+        while n.parent is not None:
+            n = n.parent
+        return n
+
+
+class ObjectTree:
+    '''
+    A tree of the armature objects based on their hierarchy.
+    '''
+    def __init__(self, objects: Iterable[Object]):
+        self.root_nodes: list[ObjectNode] = []
+        object_node_map: dict[Object, ObjectNode] = {x: ObjectNode(x) for x in objects}
+        
+        for obj, object_node in object_node_map.items():
+            if obj.parent in object_node_map:
+                parent_node = object_node_map[obj.parent]
+                object_node.parent = parent_node
+                parent_node.children.append(object_node)
+            else:
+                self.root_nodes.append(object_node)
+
+    def __iter__(self):
+        """
+        An depth-first iterator over the armature tree.
+        """
+        node_stack = [] + self.root_nodes
+        while node_stack:
+            node = node_stack.pop()
+            yield node
+            node_stack = node.children + node_stack
+    
+    def objects_iterator(self):
+        for node in self:
+            yield node.object
+    
+    def dump(self):
+        # Print out the hierarchy of armature objects for debugging using the root nodes, with indentation to show parent-child relationships.
+        for root_node in self.root_nodes:
+            def print_object_node(node: ObjectNode, indent: int = 0):
+                print(' ' * indent + f'- {node.object.name}')
+                for child_node in node.children:
+                    print_object_node(child_node, indent + 2)
+            print_object_node(root_node)
+
+
+def create_psx_bones(
+        armature_objects: list[Object],
+        export_space: str = 'WORLD',
+        forward_axis: str = 'X',
+        up_axis: str = 'Z',
+        scale: float = 1.0,
+        bone_filter_mode: str = 'ALL',
+        bone_collection_indices: list[PsxBoneCollection] | None = None,
+        bone_collection_primary_key: str = 'OBJECT',
+) -> PsxBoneCreateResult:
+    """
+    Creates a list of PSX bones from the given armature objects and options.
+    This function will throw a RuntimeError if multiple armature objects are passed in and the export space is not WORLD.
+    It will also throw a RuntimeError if the bone names are not unique when compared case-insensitively.
+    """
+    if bone_collection_indices is None:
+        bone_collection_indices = []
+
+    armature_tree = ObjectTree(armature_objects)
+
+    if len(armature_tree.root_nodes) >= 2:
+        root_bone_names = []
+        for root_node in armature_tree.root_nodes:
+            root_bone_names.append(root_node.object.name)
+        raise RuntimeError(
+            f'Multiple root armature objects were found: {root_bone_names}.\n'
+            'Only one root armature object is allowed.\n'
+            'To use multiple armature objects, parent them to one another in a hierarchy using Bone parenting.'
+        )
+
+    # TODO: confirm this to be working with non-bone parented armature hierarchies.
+
+    total_bone_count = 0
+    for armature_object in filter(lambda x: x.data is not None, armature_objects):
+        armature_data = typing_cast(Armature, armature_object.data)
+        total_bone_count += len(armature_data.bones)
+
+    # Store the bone names to be exported for each armature object.
+    armature_object_bone_names: dict[Object, list[str]] = dict()
+    for armature_object in  armature_objects:
+        armature_bone_collection_indices: list[int] = []
+        match bone_collection_primary_key:
+            case 'OBJECT':
+                armature_bone_collection_indices.extend([x.index for x in bone_collection_indices if x.armature_object_name == armature_object.name])
+            case 'DATA':
+                armature_bone_collection_indices.extend([x.index for x in bone_collection_indices if armature_object.data and x.armature_data_name == armature_object.data.name])
+            case _:
+                assert False, f'Invalid primary key: {bone_collection_primary_key}'
+        bone_names = get_export_bone_names(armature_object, bone_filter_mode, armature_bone_collection_indices)
+        armature_object_bone_names[armature_object] = bone_names
+
+    # Store the index of the root bone for each armature object.
+    # We will need this later to correctly assign vertex weights.
+    armature_object_root_bone_indices: dict[Object | None, int] = dict()
+    bones: list[PsxBoneResult] = []
+
+    # Iterate through all the armature objects.
+    for armature_object in armature_objects:
+        bone_names = armature_object_bone_names[armature_object]
+        armature_data = typing_cast(Armature, armature_object.data)
+        armature_bones = [armature_data.bones[bone_name] for bone_name in bone_names]
+
+        # Ensure that we don't have multiple root bones in this armature.
+        root_bone_count = sum(1 for bone in armature_bones if bone.parent is None)
+        if root_bone_count > 1:
+            raise RuntimeError(f'Armature object \'{armature_object.name}\' has multiple root bones. '
+                               f'Only one root bone is allowed per armature.'
+                               )
+
+        armature_psx_bones = create_psx_bones_from_blender_bones(
+            bones=armature_bones,
+            armature_object_matrix_world=armature_object.matrix_world,
+        )
+
+        if len(armature_psx_bones) == 0:
+            continue
+
+        # We have the bones in world space. If we are attaching this armature to a parent bone, we need to convert
+        # the root bone to be relative to the target parent bone.
+        if armature_object.parent in armature_objects:
+            match armature_object.parent_type:
+                case 'BONE':
+                    # Parent to a bone in the parent armature object.
+                    # We just need to get the world-space location of each of the bones and get the relative pose, then
+                    # assign that location and rotation to the root bone.
+                    parent_bone_name = armature_object.parent_bone
+
+                    if parent_bone_name == '':
+                        raise RuntimeError(f'Armature object \'{armature_object.name}\' is parented to a bone but no parent bone name is specified.')
+
+                    parent_armature_data = typing_cast(Armature, armature_object.parent.data)
+                    if parent_armature_data is None:
+                        raise RuntimeError(f'Parent object \'{armature_object.parent.name}\' is not an armature.')
+                    try:
+                        parent_bone = parent_armature_data.bones[parent_bone_name]
+                    except KeyError:
+                        raise RuntimeError(f'Bone \'{parent_bone_name}\' could not be found in armature \'{armature_object.parent.name}\'.')    
+                    
+                    parent_bone_world_matrix = armature_object.parent.matrix_world @ parent_bone.matrix_local.to_4x4()
+                    parent_bone_world_location, parent_bone_world_rotation, _ = parent_bone_world_matrix.decompose()
+
+                    # Convert the root bone location to be relative to the parent bone.
+                    root_bone = armature_psx_bones[0]
+                    root_bone_location = Vector((root_bone.location.x, root_bone.location.y, root_bone.location.z))
+                    relative_location = parent_bone_world_rotation.inverted() @ (root_bone_location - parent_bone_world_location)
+                    root_bone.location = convert_vector_to_vector3(relative_location)
+                    # Convert the root bone rotation to be relative to the parent bone.
+                    root_bone_rotation = BpyQuaternion((root_bone.rotation.w, root_bone.rotation.x, root_bone.rotation.y, root_bone.rotation.z))
+                    relative_rotation = parent_bone_world_rotation.inverted() @ root_bone_rotation
+                    root_bone.rotation = convert_bpy_quaternion_to_psx_quaternion(relative_rotation)
+                case _:
+                    raise RuntimeError(f'Unhandled parent type ({armature_object.parent_type}) for object {armature_object.name}.\n'
+                                        f'Parent type must be \'Bone\'.'
+                                        )
+
+        # If we are appending these bones to an existing list of bones, we need to adjust the parent indices for
+        # all the non-root bones.
+        if len(bones) > 0:
+            parent_index_offset = len(bones)
+            for bone in armature_psx_bones[1:]:
+                bone.parent_index += parent_index_offset
+
+        armature_object_root_bone_indices[armature_object] = len(bones)
+
+        bones.extend(PsxBoneResult(psx_bone, armature_object) for psx_bone in armature_psx_bones)
+
+    # Check that we have any bones to export at this point. If not, we can skip the rest of the processing.
+    if len(bones) == 0:
+        return PsxBoneCreateResult(
+            bones=[],
+            armature_object_root_bone_indices=armature_object_root_bone_indices,
+            armature_object_bone_names=armature_object_bone_names,
+        )
+
+    # Check if any of the armatures are parented to one another.
+    # If so, adjust the hierarchy as though they are part of the same armature object.
+    # This will let us re-use rig components without destructively joining them.
+    for armature_object in armature_objects:
+        if armature_object.parent not in armature_objects:
+            continue
+
+        # This armature object is parented to another armature object that we are exporting.
+        # First fetch the root bone indices for the two armature objects.
+        root_bone_index = armature_object_root_bone_indices.get(armature_object, None)
+        parent_root_bone_index = armature_object_root_bone_indices.get(armature_object.parent, None)
+
+        if root_bone_index is None or parent_root_bone_index is None:
+            raise RuntimeError(f'Could not find root bone index for armature object \'{armature_object.name}\' or its parent \'{armature_object.parent.name}\'.\n'
+                               'This likely means that one of the armatures does not have any bones that are being exported, which is not allowed when using armature parenting between multiple armatures.'
+                               )
+
+        match armature_object.parent_type:
+            case 'OBJECT':
+                # Parent this armature's root bone to the root bone of the parent object.
+                bones[root_bone_index].psx_bone.parent_index = parent_root_bone_index
+            case 'BONE':
+                # Parent this armature's root bone to the specified bone in the parent.
+                new_parent_index = None
+                for bone_index, bone in enumerate(bones):
+                    if bone.psx_bone.name == convert_string_to_cp1252_bytes(armature_object.parent_bone) and bone.armature_object == armature_object.parent:
+                        new_parent_index = bone_index
+                        break
+                if new_parent_index == None:
+                    raise RuntimeError(f'Bone \'{armature_object.parent_bone}\' could not be found in armature \'{armature_object.parent.name}\'.')
+                bones[root_bone_index].psx_bone.parent_index = new_parent_index
+            case _:
+                raise RuntimeError(f'Unhandled parent type ({armature_object.parent_type}) for object {armature_object.name}.\n'
+                                    f'Parent type must be \'Object\' or \'Bone\'.'
+                                    )
+
+    match export_space:
+        case 'WORLD':
+            # No action needed, bones are already in world space.
+            pass
+        case 'ARMATURE':
+            # The bone is in world-space. We need to convert it to armature (object) space.
+            # Get this from matrix_local.
+            root_bone, root_bone_armature_object = bones[0].psx_bone, bones[0].armature_object
+            if root_bone_armature_object is None:
+                raise RuntimeError('Cannot export to Armature space when multiple armatures are being exported.')
+        
+            armature_data = typing_cast(Armature, root_bone_armature_object.data)
+            matrix_local = armature_data.bones[root_bone.name.decode('windows-1252')].matrix_local
+            location, rotation, _ = matrix_local.decompose()
+            root_bone.location = convert_vector_to_vector3(location)
+            root_bone.rotation = convert_bpy_quaternion_to_psx_quaternion(rotation)
+        case 'ROOT':
+            # Zero out the root bone transforms.
+            root_bone = bones[0].psx_bone
+            root_bone.location = Vector3.zero()
+            root_bone.rotation = Quaternion.identity()
+        case _:
+            assert False, f'Invalid export space: {export_space}'
+
+    # Check if there are bone name conflicts between armatures.
+    bone_name_counts = Counter(bone.psx_bone.name.decode('windows-1252').upper() for bone in bones)
+    for bone_name, count in bone_name_counts.items():
+        if count > 1:
+            raise RuntimeError(
+                f'Found {count} bones with the name "{bone_name}". '
+                f'Bone names must be unique when compared case-insensitively.'
+            )
+    
+    # Apply the scale to the bone locations.
+    for bone in bones:
+        bone.psx_bone.location.x *= scale
+        bone.psx_bone.location.y *= scale
+        bone.psx_bone.location.z *= scale
+    
+    coordinate_system_matrix = get_coordinate_system_transform(forward_axis, up_axis)
+    coordinate_system_default_rotation = coordinate_system_matrix.to_quaternion()
+
+    # Apply the coordinate system transform to the root bone.
+    root_psx_bone = bones[0].psx_bone
+    # Get transform matrix from root bone location and rotation.
+    root_bone_location = Vector((root_psx_bone.location.x, root_psx_bone.location.y, root_psx_bone.location.z))
+    root_bone_rotation = BpyQuaternion((root_psx_bone.rotation.w, root_psx_bone.rotation.x, root_psx_bone.rotation.y, root_psx_bone.rotation.z))
+    root_bone_matrix = (
+        Matrix.Translation(root_bone_location) @
+        root_bone_rotation.to_matrix().to_4x4()
+    )
+    root_bone_matrix = coordinate_system_default_rotation.inverted().to_matrix().to_4x4() @ root_bone_matrix
+    location, rotation, _ = root_bone_matrix.decompose()
+    root_psx_bone.location = convert_vector_to_vector3(location)
+    root_psx_bone.rotation = convert_bpy_quaternion_to_psx_quaternion(rotation)
+
+    convert_bpy_quaternion_to_psx_quaternion(coordinate_system_default_rotation)
+
+    return PsxBoneCreateResult(
+        bones=bones,
+        armature_object_root_bone_indices=armature_object_root_bone_indices,
+        armature_object_bone_names=armature_object_bone_names,
+    )
+
+
+def get_vector_from_axis_identifier(axis_identifier: str) -> Vector:
+    match axis_identifier:
+        case 'X':
+            return Vector((1.0, 0.0, 0.0))
+        case 'Y':
+            return Vector((0.0, 1.0, 0.0))
+        case 'Z':
+            return Vector((0.0, 0.0, 1.0))
+        case '-X':
+            return Vector((-1.0, 0.0, 0.0))
+        case '-Y':
+            return Vector((0.0, -1.0, 0.0))
+        case '-Z':
+            return Vector((0.0, 0.0, -1.0))
+        case _:
+            assert False, f'Invalid axis identifier: {axis_identifier}'
+
+
+def get_coordinate_system_transform(forward_axis: str = 'X', up_axis: str = 'Z') -> Matrix:
+    forward = get_vector_from_axis_identifier(forward_axis)
+    up = get_vector_from_axis_identifier(up_axis)
+    left = up.cross(forward)
+    return Matrix((
+        (forward.x, forward.y, forward.z, 0.0),
+        (left.x, left.y, left.z, 0.0),
+        (up.x, up.y, up.z, 0.0),
+        (0.0, 0.0, 0.0, 1.0)
+    ))
+
+
+def get_armatures_for_mesh_objects(mesh_objects: Iterable[Object]):
+    """
+    Returns a generator of unique armature objects that are used by the given mesh objects.
+    """
+    armature_objects: set[Object] = set()
+    for mesh_object in mesh_objects:
+        armature_modifiers = [typing_cast(ArmatureModifier, x) for x in mesh_object.modifiers if x.type == 'ARMATURE']
+        for armature_object in map(lambda x: x.object, armature_modifiers):
+            if armature_object is not None:
+                armature_objects.add(armature_object)
+    yield from armature_objects
+
+
+def get_collection_from_context(context: Context) -> Collection | None:
+    if context.space_data is None or context.space_data.type != 'PROPERTIES':
+        return None
+    space_data = typing_cast(SpaceProperties, context.space_data)
+    if space_data.use_pin_id:
+        return typing_cast(Collection, space_data.pin_id)
+    else:
+        return context.collection
+
+
+def get_collection_export_operator_from_context(context: Context) -> PropertyGroup | None:
+    collection = get_collection_from_context(context)
+    if collection is None or collection.active_exporter_index is None:
+        return None
+    if 0 > collection.active_exporter_index >= len(collection.exporters):
+        return None
+    exporter = collection.exporters[collection.active_exporter_index]
+    return exporter.export_properties
+
+
+from ..shared.dfs import DfsObject, dfs_collection_objects, dfs_view_layer_objects
+from typing import Set
+from bpy.types import Depsgraph
+
+
+class PskInputObjects(object):
+    def __init__(self):
+        self.mesh_dfs_objects: list[DfsObject] = []
+        self.armature_objects: list[Object] = []
+
+
+def get_materials_for_mesh_objects(depsgraph: Depsgraph, mesh_objects: Iterable[Object]):
+    '''
+    Yields unique materials used by the given mesh objects.
+    If any mesh has no material slots or any empty material slots, None is yielded at the end.
+    '''
+    yielded_materials: Set[Material] = set()
+    has_none_material = False
+    for mesh_object in mesh_objects:
+        evaluated_mesh_object = mesh_object.evaluated_get(depsgraph)
+        # Check if mesh has no material slots or any empty material slots
+        if len(evaluated_mesh_object.material_slots) == 0:
+            has_none_material = True
+        else:
+            for material_slot in evaluated_mesh_object.material_slots:
+                material = material_slot.material
+                if material is None:
+                    has_none_material = True
+                else:
+                    if material not in yielded_materials:
+                        yielded_materials.add(material)
+                        yield material
+    # Yield None at the end if any mesh had no material slots or empty material slots
+    if has_none_material:
+        yield None
+
+
+def get_mesh_objects_for_collection(collection: Collection) -> Iterable[DfsObject]:
+    return filter(lambda x: x.obj.type == 'MESH', dfs_collection_objects(collection))
+
+
+def get_mesh_objects_for_context(context: Context) -> Iterable[DfsObject]:
+    if context.view_layer is None:
+        return
+    for dfs_object in dfs_view_layer_objects(context.view_layer):
+        if dfs_object.obj.type == 'MESH' and dfs_object.is_selected:
+            yield dfs_object
+
+
+def get_armature_for_mesh_object(mesh_object: Object) -> Object | None:
+    if mesh_object.type != 'MESH':
+        return None
+    # Get the first armature modifier with a non-empty armature object.
+    for modifier in filter(lambda x: x.type == 'ARMATURE', mesh_object.modifiers):
+            armature_modifier = typing_cast(ArmatureModifier, modifier)
+            if armature_modifier.object is not None:
+                return armature_modifier.object
+    return None
+
+
+def _get_psk_input_objects(mesh_dfs_objects: Iterable[DfsObject]) -> PskInputObjects:
+    mesh_dfs_objects = list(mesh_dfs_objects)
+    if len(mesh_dfs_objects) == 0:
+        raise RuntimeError('No mesh objects were found to export.')
+    input_objects = PskInputObjects()
+    input_objects.mesh_dfs_objects = mesh_dfs_objects
+    # Get the armature objects used on all the meshes being exported.
+    armature_objects = get_armatures_for_mesh_objects(map(lambda x: x.obj, mesh_dfs_objects))
+    # Sort them in hierarchy order.
+    input_objects.armature_objects = list(ObjectTree(armature_objects).objects_iterator())
+    return input_objects
+
+
+def get_psk_input_objects_for_context(context: Context) -> PskInputObjects:
+    mesh_objects = list(get_mesh_objects_for_context(context))
+    return _get_psk_input_objects(mesh_objects)
+
+
+def get_psk_input_objects_for_collection(collection: Collection) -> PskInputObjects:
+    mesh_objects = get_mesh_objects_for_collection(collection)
+    return _get_psk_input_objects(mesh_objects)

io_scene_psk_psa/shared/operators.py

@@ -0,0 +1,72 @@
+from bpy.types import Operator
+from bpy.props import BoolProperty
+
+from .types import PsxBoneExportMixin
+from typing import cast as typing_cast
+
+from .helpers import get_collection_export_operator_from_context, get_psk_input_objects_for_collection, populate_bone_collection_list
+
+
+
+class PSK_OT_bone_collection_list_populate(Operator):
+    bl_idname = 'psk.bone_collection_list_populate'
+    bl_label = 'Populate Bone Collection List'
+    bl_description = 'Populate the bone collection list from the armature that will be used in this collection export'
+    bl_options = {'INTERNAL'}
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        if context.collection is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No active collection')
+            return {'CANCELLED'}
+        try:
+            input_objects = get_psk_input_objects_for_collection(context.collection)
+        except RuntimeError as e:
+            self.report({'ERROR_INVALID_CONTEXT'}, str(e))
+            return {'CANCELLED'}
+        if not input_objects.armature_objects:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No armature modifiers found on mesh objects')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PsxBoneExportMixin, export_operator)
+
+        # Save and restore the selected status of the bones collections.
+        selected_status: dict[int, bool] = dict()
+        for bone_collection in export_operator.bone_collection_list:
+            selected_status[hash(bone_collection)] = bone_collection.is_selected
+
+        populate_bone_collection_list(export_operator.bone_collection_list, input_objects.armature_objects)
+
+        for bone_collection in export_operator.bone_collection_list:
+            bone_collection.is_selected = selected_status.get(hash(bone_collection), False)
+
+        return {'FINISHED'}
+
+
+class PSK_OT_bone_collection_list_select_all(Operator):
+    bl_idname = 'psk.bone_collection_list_select_all'
+    bl_label = 'Select All'
+    bl_description = 'Select all bone collections'
+    bl_options = {'INTERNAL'}
+
+    is_selected: BoolProperty(default=True)
+
+    def execute(self, context):
+        export_operator = get_collection_export_operator_from_context(context)
+        if export_operator is None:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No valid export operator found in context')
+            return {'CANCELLED'}
+        export_operator = typing_cast(PsxBoneExportMixin, export_operator)
+        for item in export_operator.bone_collection_list:
+            item.is_selected = self.is_selected
+        return {'FINISHED'}
+
+
+_classes = (
+    PSK_OT_bone_collection_list_populate,
+    PSK_OT_bone_collection_list_select_all,
+)
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/shared/types.py

@@ -0,0 +1,197 @@
+from typing import Generic, Iterable, Sized, TypeVar
+import bpy
+from bpy.props import CollectionProperty, EnumProperty, StringProperty, IntProperty, BoolProperty, FloatProperty
+from bpy.types import PropertyGroup, UIList, UILayout, Context, AnyType, Panel
+
+T = TypeVar('T')
+
+# Don't actually use this, this is just for typing.
+class BpyCollectionProperty(Generic[T], Iterable[T], Sized):
+    def add(self) -> T:
+        return T() # type: ignore
+
+    def clear(self) -> None:
+        pass
+
+    def move(self, src_index: int, dst_index: int):
+        pass
+
+    def remove(self, index: int):
+        pass
+
+
+class PSX_UL_bone_collection_list(UIList):
+
+    def draw_item(self, context: Context, layout: UILayout, data: AnyType, item: AnyType, icon: int,
+                  active_data: AnyType, active_property: str, index: int = 0, flt_flag: int = 0):
+        row = layout.row()
+
+        row.prop(item, 'is_selected', text=getattr(item, 'name'))
+        row.label(text=str(getattr(item, 'count')), icon='BONE_DATA')
+
+        armature_object = bpy.data.objects.get(item.armature_object_name, None)
+        if armature_object is None:
+            row.label(icon='ERROR')
+        else:
+            row.label(text=armature_object.name, icon='ARMATURE_DATA')
+
+
+class PSX_PG_bone_collection_list_item(PropertyGroup):
+    armature_object_name: StringProperty()
+    armature_data_name: StringProperty()
+    name: StringProperty()
+    index: IntProperty()
+    count: IntProperty()
+    is_selected: BoolProperty(default=False)
+
+    def __hash__(self) -> int:
+        return hash(f'{self.name}/{self.armature_object_name}/{self.armature_data_name}')
+
+
+class PSX_PG_action_export(PropertyGroup):
+    group: StringProperty(name='Group', description='The group of the sequence', maxlen=64)
+    compression_ratio: FloatProperty(name='Compression Ratio', default=1.0, min=0.0, max=1.0, subtype='FACTOR', description='The key sampling ratio of the exported sequence.\n\nA compression ratio of 1.0 will export all frames, while a compression ratio of 0.5 will export half of the frames')
+    key_quota: IntProperty(name='Key Quota', default=0, min=1, description='The minimum number of frames to be exported')
+    fps: FloatProperty(name='FPS', default=30.0, min=0.0, description='The frame rate of the exported sequence')
+
+
+class PSX_PT_action(Panel):
+    bl_idname = 'PSX_PT_action'
+    bl_label = 'PSA Export'
+    bl_space_type = 'DOPESHEET_EDITOR'
+    bl_region_type = 'UI'
+    bl_context = 'action'
+    bl_category = 'Action'
+
+    @classmethod
+    def poll(cls, context: 'Context'):
+        return context.active_object is not None and context.active_object.type == 'ARMATURE' and context.active_action is not None
+
+    def draw(self, context: 'Context'):
+        action = context.active_action
+        layout = self.layout
+        assert layout is not None
+        flow = layout.grid_flow(columns=1)
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+        psa_export = getattr(action, 'psa_export')
+        assert psa_export
+        flow.prop(psa_export, 'compression_ratio')
+        flow.prop(psa_export, 'key_quota')
+        flow.prop(psa_export, 'fps')
+        flow.prop(psa_export, 'group', placeholder='Group')
+
+
+bone_filter_mode_items = (
+    ('ALL', 'All', 'All bones will be exported'),
+    ('BONE_COLLECTIONS', 'Bone Collections', 'Only bones belonging to the selected bone collections and their ancestors will be exported')
+)
+
+axis_identifiers = ('X', 'Y', 'Z', '-X', '-Y', '-Z')
+forward_items = (
+    ('X', 'X Forward', ''),
+    ('Y', 'Y Forward', ''),
+    ('Z', 'Z Forward', ''),
+    ('-X', '-X Forward', ''),
+    ('-Y', '-Y Forward', ''),
+    ('-Z', '-Z Forward', ''),
+)
+
+up_items = (
+    ('X', 'X Up', ''),
+    ('Y', 'Y Up', ''),
+    ('Z', 'Z Up', ''),
+    ('-X', '-X Up', ''),
+    ('-Y', '-Y Up', ''),
+    ('-Z', '-Z Up', ''),
+)
+
+
+def forward_axis_update(self, context):
+    if self.forward_axis == self.up_axis:
+        # Automatically set the up axis to the next available axis
+        self.up_axis = next((axis for axis in axis_identifiers if axis != self.forward_axis), 'Z')
+
+
+def up_axis_update(self, context):
+    if self.up_axis == self.forward_axis:
+        # Automatically set the forward axis to the next available axis
+        self.forward_axis = next((axis for axis in axis_identifiers if axis != self.up_axis), 'X')
+
+
+class AxisMixin:
+    forward_axis: EnumProperty(
+        name='Forward',
+        items=forward_items,
+        default='X',
+        update=forward_axis_update
+    )
+    up_axis: EnumProperty(
+        name='Up',
+        items=up_items,
+        default='Z',
+        update=up_axis_update
+    )
+
+
+class TransformMixin(AxisMixin):
+    scale: FloatProperty(
+        name='Scale',
+        default=1.0,
+        description='Scale factor to apply to all location data',
+        soft_min=0.0,
+        soft_max=100.0
+    )
+
+
+export_space_items = [
+    ('WORLD', 'World', 'Export in world space'),
+    ('ARMATURE', 'Armature', 'Export the local space of the armature object'),
+    ('ROOT', 'Root', 'Export in the space of the root bone')
+]
+
+
+class ExportSpaceMixin:
+    export_space: EnumProperty(
+        name='Export Space',
+        items=export_space_items,
+        default='WORLD'
+    )
+ 
+transform_source_items = (
+    ('SCENE', 'Scene', 'Use the scene transform settings'),
+    ('CUSTOM', 'Custom', 'Use custom transform settings'),
+)
+
+class TransformSourceMixin:
+    transform_source: EnumProperty(
+        items=transform_source_items,
+        name='Transform Source',
+        default='SCENE'
+    )
+ 
+class PsxBoneExportMixin:
+    bone_filter_mode: EnumProperty(
+        name='Bone Filter',
+        options=set(),
+        description='',
+        items=bone_filter_mode_items,
+    )
+    bone_collection_list: CollectionProperty(type=PSX_PG_bone_collection_list_item)
+    bone_collection_list_index: IntProperty(default=0, name='', description='')
+
+
+class PSX_PG_scene_export(PropertyGroup, TransformMixin):
+    pass
+
+
+_classes = (
+    PSX_PG_scene_export,
+    PSX_PG_action_export,
+    PSX_PG_bone_collection_list_item,
+    PSX_UL_bone_collection_list,
+    PSX_PT_action,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)

io_scene_psk_psa/shared/types.pyi

@@ -0,0 +1,62 @@
+from typing import Generic, TypeVar, Iterable, Sized
+
+T = TypeVar("T")
+
+# https://docs.blender.org/api/current/bpy.types.bpy_prop_collection_idprop.html#bpy.types.bpy_prop_collection_idprop
+class BpyCollectionProperty(Generic[T], Iterable[T], Sized):
+    def add(self) -> T:
+        pass
+
+    def clear(self) -> None:
+        pass
+
+    def move(self, src_index: int, dst_index: int):
+        pass
+
+    def remove(self, index: int):
+        pass
+
+
+class PSX_PG_bone_collection_list_item:
+    armature_object_name: str
+    armature_data_name: str
+    name: str
+    index: int
+    count: int
+    is_selected: bool
+
+
+class PSX_PG_action_export:
+    group: str
+    compression_ratio: float
+    key_quota: int
+    fps: float
+
+
+class AxisMixin:
+    forward_axis: str
+    up_axis: str
+
+
+class TransformMixin(AxisMixin):
+    scale: float
+
+
+class ExportSpaceMixin:
+    export_space: str
+
+
+class TransformSourceMixin:
+    transform_source: str
+
+
+class PsxBoneExportMixin:
+    bone_filter_mode: str
+    bone_collection_list: BpyCollectionProperty[PSX_PG_bone_collection_list_item]
+    bone_collection_list_index: int
+
+
+class PSX_PG_scene_export(TransformSourceMixin):
+    pass
+
+bone_filter_mode_items: tuple[tuple[str, str, str]]

io_scene_psk_psa/shared/ui.py

@@ -0,0 +1,59 @@
+import bpy
+from bpy.types import Context, UILayout, Panel
+
+from .types import bone_filter_mode_items
+
+
+def is_bone_filter_mode_item_available(pg, identifier):
+    if identifier == 'BONE_COLLECTIONS' and len(pg.bone_collection_list) == 0:
+        return False
+    return True
+
+
+def draw_bone_filter_mode(layout: UILayout, pg, should_always_show_bone_collections=False):
+    row = layout.row(align=True)
+    for item_identifier, _, _ in bone_filter_mode_items:
+        identifier = item_identifier
+        item_layout = row.row(align=True)
+        item_layout.prop_enum(pg, 'bone_filter_mode', item_identifier)
+        item_layout.enabled = should_always_show_bone_collections or is_bone_filter_mode_item_available(pg, identifier)
+
+
+class PSX_PT_scene(Panel):
+    bl_idname = 'PSX_PT_scene'
+    bl_label = 'PSK Export'
+    bl_space_type = 'PROPERTIES'
+    bl_region_type = 'WINDOW'
+    bl_context = 'scene'
+    bl_category = 'PSK/PSA'
+
+    @classmethod
+    def poll(cls, context):
+        return context.scene is not None
+    
+    def draw(self, context: Context):
+        layout = self.layout
+        scene = bpy.context.scene
+        psx_export = getattr(scene, 'psx_export', None)
+        if psx_export is None:
+            return
+        
+        # Transform
+        transform_header, transform_panel = layout.panel('Transform', default_closed=False)
+        transform_header.label(text='Transform')
+        if transform_panel:
+            flow = layout.grid_flow(columns=1)
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(psx_export, 'scale')
+            flow.prop(psx_export, 'forward_axis')
+            flow.prop(psx_export, 'up_axis')
+
+
+_classes = (
+    PSX_PT_scene,
+)
+
+from bpy.utils import register_classes_factory
+register, unregister = register_classes_factory(_classes)
+

pyproject.toml

@@ -0,0 +1,15 @@
+[project]
+name = "io_scene_psk_psa"
+
+[pytest]
+blender-addons-dirs = "io_scene_psk_psa"
+testpaths = "../tests"
+
+[tool.coverage.run]
+branch = true
+
+[tool.coverage.report]
+ignore_errors = true
+
+[tool.pyright]
+reportInvalidTypeForm = false

test.sh

@@ -0,0 +1,35 @@
+#!/usr/bin/env bash
+
+# Exit immediately if a command exits with a non-zero status
+set -e
+
+# Function to find an available container command (podman or docker)
+find_container_cli() {
+    if command -v podman &> /dev/null; then
+        echo "podman"
+    elif command -v docker &> /dev/null; then
+        echo "docker"
+    else
+        echo ""
+    fi
+}
+
+CONTAINER_CLI=$(find_container_cli)
+
+if [ -z "$CONTAINER_CLI" ]; then
+    echo "Error: Neither Podman nor Docker was found. Please install one of them to proceed."
+    exit 1
+fi
+
+echo "Using container CLI: $CONTAINER_CLI"
+
+# Build the image and capture its ID
+# The '-q' flag is supported by both podman and docker build to suppress output and return only the image ID.
+IMAGE_ID=$($CONTAINER_CLI build -q .)
+
+# Run the container using the selected CLI and captured image ID
+$CONTAINER_CLI run -it \
+    --volume "${PWD}:/io_scene_psk_psa:z" \
+    --volume "${PWD}/io_scene_psk_psa:/addons/io_scene_psk_psa:z" \
+    --volume "${PWD}/tests:/tests:z" \
+    "$IMAGE_ID"

tests/psa_import_test.py

@@ -0,0 +1,65 @@
+import bpy
+import pytest
+
+SHREK_PSK_FILEPATH = 'tests/data/Shrek.psk'
+SHREK_PSA_FILEPATH = 'tests/data/Shrek.psa'
+
+
+@pytest.fixture(autouse=True)
+def run_before_and_after_Tests(tmpdir):
+    # Setup: Run before the tests
+    bpy.ops.wm.read_homefile(app_template='')
+    yield
+    # Teardown: Run after the tests
+    pass
+
+
+def test_psa_import_all():
+    assert bpy.ops.psk.import_file(
+        filepath=SHREK_PSK_FILEPATH,
+        components='ALL',
+        ) == {'FINISHED'}, "PSK import failed."
+
+    armature_object = bpy.data.objects.get('Shrek', None)
+    assert armature_object is not None, "Armature object not found in the scene."
+    assert armature_object.type == 'ARMATURE', "Object is not of type ARMATURE."
+
+    # Select the armature object
+    bpy.context.view_layer.objects.active = armature_object
+    armature_object.select_set(True)
+
+    # Import the associated PSA file with import_all operator.
+    assert bpy.ops.psa.import_all(
+        filepath=SHREK_PSA_FILEPATH
+        ) == {'FINISHED'}, "PSA import failed."
+    
+    # TODO: More thorough tests on the imported data for the animations.
+    EXPECTED_ACTION_COUNT = 135
+    assert len(bpy.data.actions) == EXPECTED_ACTION_COUNT, \
+        f"Expected {EXPECTED_ACTION_COUNT} actions, but found {len(bpy.data.actions)}."
+
+
+def test_psa_import_convert_to_samples():
+    assert bpy.ops.psk.import_file(
+        filepath=SHREK_PSK_FILEPATH,
+        components='ALL',
+        ) == {'FINISHED'}, "PSK import failed."
+
+    armature_object = bpy.data.objects.get('Shrek', None)
+    assert armature_object is not None, "Armature object not found in the scene."
+    assert armature_object.type == 'ARMATURE', "Object is not of type ARMATURE."
+
+    # Select the armature object
+    bpy.context.view_layer.objects.active = armature_object
+    armature_object.select_set(True)
+
+    # Import the associated PSA file with import_all operator, and convert to samples.
+    assert bpy.ops.psa.import_all(
+        filepath=SHREK_PSA_FILEPATH,
+        should_convert_to_samples=True
+        ) == {'FINISHED'}, "PSA import failed."
+    
+    # TODO: More thorough tests on the imported data for the animations.
+    EXPECTED_ACTION_COUNT = 135
+    assert len(bpy.data.actions) == EXPECTED_ACTION_COUNT, \
+        f"Expected {EXPECTED_ACTION_COUNT} actions, but found {len(bpy.data.actions)}."

tests/psk_export_test.py

@@ -0,0 +1,62 @@
+import bpy
+import pytest
+import tempfile
+from psk_psa_py.psk.reader import read_psk_from_file
+
+
+@pytest.fixture(autouse=True)
+def run_before_and_after_tests(tmpdir):
+    # Setup: Run before the tests
+    bpy.ops.wm.read_homefile(filepath='tests/data/psk_export_tests.blend')
+
+    yield
+    # Teardown: Run after the tests
+    pass
+
+
+def export_psk_and_read_back(collection_name: str):
+    collection = bpy.data.collections.get(collection_name, None)
+    assert collection is not None, f"Collection {collection_name} not found in the scene."
+
+    # Select the collection to make it the active collection.
+    view_layer = bpy.context.view_layer
+    assert view_layer is not None, "No active view layer found."
+    view_layer.active_layer_collection = view_layer.layer_collection.children[collection_name]
+
+    filepath = str(tempfile.gettempdir() + f'/{collection_name}.psk')
+
+    collection.exporters[0].filepath = filepath
+
+    assert bpy.ops.collection.exporter_export() == {'FINISHED'}, "PSK export failed."
+
+    # Now load the exported PSK file and return its contents.
+    psk = read_psk_from_file(filepath)
+    return psk
+
+
+def test_psk_export_cube_no_bones():
+    psk = export_psk_and_read_back('cube_no_bones')
+
+    # There should be one bone when no armature is present, this is added automatically to serve as the root bone for the mesh.
+    assert len(psk.bones) == 1, f"Expected 1 bone, but found {len(psk.bones)}."
+    assert len(psk.points) == 8, f"Expected 8 points, but found {len(psk.points)}."
+    assert len(psk.faces) == 12, f"Expected 12 faces, but found {len(psk.faces)}."
+    assert len(psk.materials) == 1, f"Expected 1 material, but found {len(psk.materials)}."
+
+
+def test_cube_edge_split():
+    # The cube has all the edges set to split with a modifier.
+    psk = export_psk_and_read_back('cube_edge_split')
+
+    assert len(psk.bones) == 1, f"Expected 1 bone, but found {len(psk.bones)}."
+    assert len(psk.points) == 24, f"Expected 24 points, but found {len(psk.points)}."
+    assert len(psk.faces) == 12, f"Expected 12 faces, but found {len(psk.faces)}."
+    assert len(psk.materials) == 1, f"Expected 1 material, but found {len(psk.materials)}."
+
+
+def test_cube_with_simple_armature():
+    # The cube has all the edges set to split with a modifier.
+    psk = export_psk_and_read_back('cube_with_simple_armature')
+
+    assert len(psk.bones) == 1, f"Expected 1 bone, but found {len(psk.bones)}."
+    assert psk.bones[0].name == b'ROOT', f"Expected bone name 'ROOT', but found {psk.bones[0].name}."

tests/psk_import_test.py

@@ -0,0 +1,340 @@
+import bpy
+import pytest
+
+from typing import cast as typing_cast
+from bpy.types import Mesh, Armature
+
+SUZANNE_FILEPATH = 'tests/data/Suzanne.psk'
+SARGE_FILEPATH = 'tests/data/CS_Sarge_S0_Skelmesh.pskx'
+SLURP_MONSTER_AXE_FILEPATH = 'tests/data/Slurp_Monster_Axe_LOD0.psk'
+BAT_FILEPATH = 'tests/data/Bat.psk'
+BLACK_WIDOW_FILEPATH = 'tests/data/SK_1033_1033001.pskx'
+
+
+@pytest.fixture(autouse=True)
+def run_before_and_after_Tests(tmpdir):
+    # Setup: Run before the tests
+    bpy.ops.wm.read_homefile(app_template='')
+    yield
+    # Teardown: Run after the tests
+    pass
+
+
+def test_psk_import_all():
+    assert bpy.ops.psk.import_file(
+        filepath=SUZANNE_FILEPATH,
+        components='ALL',
+        ) == {'FINISHED'}
+
+    armature_object = bpy.data.objects.get('Suzanne', None)
+
+    assert armature_object is not None, "Armature object not found in the scene"
+    assert armature_object.type == 'ARMATURE', "Armature object type should be ARMATURE"
+    assert armature_object is not None, "Armature object not found in the scene"
+    assert len(armature_object.children) == 1, "Armature object should have one child"
+
+    armature_data = typing_cast(Armature, armature_object.data)
+
+    assert len(armature_data.bones) == 1, "Armature should have one bone"
+
+    mesh_object = bpy.data.objects.get('Suzanne.001', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+
+    assert len(mesh_data.vertices) == 507
+    assert len(mesh_data.polygons) == 968
+
+
+def test_psk_import_armature_only():
+    assert bpy.ops.psk.import_file(
+        filepath=SUZANNE_FILEPATH,
+        components='ARMATURE',
+        ) == {'FINISHED'}
+
+    armature_object = bpy.data.objects.get('Suzanne', None)
+
+    assert armature_object is not None, "Armature object not found in the scene"
+    assert armature_object.type == 'ARMATURE', "Armature object type should be ARMATURE"
+    assert len(armature_object.children) == 0, "Armature object should have no children"
+
+    armature_data = typing_cast(Armature, armature_object.data)
+
+    assert len(armature_data.bones) == 1, "Armature should have one bone"
+
+
+def test_psk_import_mesh_only():
+    assert bpy.ops.psk.import_file(
+        filepath=SUZANNE_FILEPATH,
+        components='MESH',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('Suzanne', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+
+    assert len(mesh_data.vertices) == 507
+    assert len(mesh_data.polygons) == 968
+
+
+def test_psk_import_scale():
+    """
+    Test the import of a PSK file with a scale factor of 2.0.
+    The scale factor is applied to the armature object.
+    """
+    assert bpy.ops.psk.import_file(
+        filepath=SUZANNE_FILEPATH,
+        components='ALL',
+        scale=2.0,
+        ) == {'FINISHED'}
+
+    armature_object = bpy.data.objects.get('Suzanne', None)
+    assert armature_object is not None, "Armature object not found in the scene"
+    assert armature_object.type == 'ARMATURE', "Armature object type should be ARMATURE"
+    assert tuple(armature_object.scale) == (2.0, 2.0, 2.0), "Armature object scale should be (2.0, 2.0, 2.0)"
+
+
+def test_psk_import_bone_length():
+    bone_length = 1.25
+
+    assert bpy.ops.psk.import_file(
+        filepath=SUZANNE_FILEPATH,
+        components='ARMATURE',
+        bone_length=bone_length,
+        ) == {'FINISHED'}
+    
+    armature_object = bpy.data.objects.get('Suzanne', None)
+    assert armature_object is not None, "Armature object not found in the scene"
+    assert armature_object.type == 'ARMATURE', "Armature object type should be ARMATURE"
+
+    armature_data = typing_cast(Armature, armature_object.data)
+    assert armature_data is not None, "Armature data not found in the scene"
+    assert len(armature_data.bones) == 1, "Armature should have one bone"
+    assert 'ROOT' in armature_data.bones, "Armature should have a bone named 'ROOT'"
+
+    root_bone = armature_data.bones['ROOT']
+    assert tuple(root_bone.head) == (0.0, 0.0, 0.0), "Bone head should be (0.0, 0.0, 0.0)"
+    assert tuple(root_bone.tail) == (0.0, bone_length, 0.0), f"Bone tail should be (0.0, {bone_length}, 0.0)"
+
+
+def test_psk_import_with_vertex_normals():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_normals=True,
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert mesh_data.has_custom_normals, "Mesh should have custom normals"
+
+
+def test_psk_import_without_vertex_normals():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_normals=False,
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert not mesh_data.has_custom_normals, "Mesh should not have custom normals"
+
+
+def test_psk_import_with_vertex_colors_srgba():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=True,
+        vertex_color_space='SRGBA',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.color_attributes) == 1, "Mesh should have one vertex color layer"
+    assert mesh_data.color_attributes[0].name == 'VERTEXCOLOR', "Vertex color layer should be named 'VERTEXCOLOR'"
+    assert tuple(mesh_data.color_attributes[0].data[3303].color) == (0.34586891531944275, 0.0, 0.0, 1.0), "Unexpected vertex color value"
+
+
+def test_psk_import_vertex_colors_linear():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=True,
+        vertex_color_space='LINEAR',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.color_attributes) == 1, "Mesh should have one vertex color layer"
+    assert mesh_data.color_attributes[0].name == 'VERTEXCOLOR', "Vertex color layer should be named 'VERTEXCOLOR'"
+    assert tuple(mesh_data.color_attributes[0].data[3303].color) == (0.09803921729326248, 0.0, 0.0, 1.0), "Unexpected vertex color value"
+
+
+def test_psk_import_without_vertex_colors():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=False,
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.color_attributes) == 0, "Mesh should not have any vertex color layers"
+
+
+def test_psk_import_extra_uvs():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=True,
+        vertex_color_space='LINEAR',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.uv_layers) == 2, "Mesh should have two UV layers"
+
+    assert mesh_data.uv_layers[0].name == 'UVMap', "First UV layer should be named 'UVMap'"
+    assert mesh_data.uv_layers[1].name == 'EXTRAUV0', "Second UV layer should be named 'EXTRAUV0'"
+
+    # Verify that the data is actually different
+    assert mesh_data.uv_layers[0].uv[0].vector.x == 0.92480468750
+    assert mesh_data.uv_layers[0].uv[0].vector.y == 0.90533447265625
+    assert mesh_data.uv_layers[1].uv[0].vector.x == 3.0517578125e-05
+    assert mesh_data.uv_layers[1].uv[0].vector.y == 0.999969482421875
+
+
+def test_psk_import_many_extra_uvs():
+    assert bpy.ops.psk.import_file(
+        filepath=BLACK_WIDOW_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=False,
+        should_import_vertex_normals=False,
+        should_import_shape_keys=False,
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('SK_1033_1033001', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.uv_layers) == 4, "Mesh should have two UV layers"
+
+    assert mesh_data.uv_layers[0].name == 'UVMap', "First UV layer should be named 'UVMap'"
+    assert mesh_data.uv_layers[1].name == 'EXTRAUV0', "Second UV layer should be named 'EXTRAUV0'"
+    assert mesh_data.uv_layers[2].name == 'EXTRAUV1', "Third UV layer should be named 'EXTRAUV1'"
+    assert mesh_data.uv_layers[3].name == 'EXTRAUV2', "Fourth UV layer should be named 'EXTRAUV2'"
+
+
+def test_psk_import_multiple_extra_uvs():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        should_import_vertex_colors=True,
+        vertex_color_space='LINEAR',
+        ) == {'FINISHED'}
+
+
+def test_psk_import_materials():
+    assert bpy.ops.psk.import_file(
+        filepath=SARGE_FILEPATH,
+        components='MESH',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('CS_Sarge_S0_Skelmesh', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+
+    assert mesh_data is not None, "Mesh data not found in the scene"
+    assert len(mesh_data.materials) == 4, "Mesh should have four materials"
+    material_names = (
+        'CS_Sarge_S0_MI',
+        'TP_Core_Eye_MI',
+        'AB_Sarge_S0_E_StimPack_MI1',
+        'CS_Sarge_S0_MI'
+    )
+    for i, material in enumerate(mesh_data.materials):
+        assert material is not None, f"Material {i} should not be None"
+        assert material.name == material_names[i], f"Material {i} name should be {material_names[i]}"
+
+
+def test_psk_import_shape_keys():
+    assert bpy.ops.psk.import_file(
+        filepath=SLURP_MONSTER_AXE_FILEPATH,
+        components='MESH',
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('Slurp_Monster_Axe_LOD0', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data should not be None"
+    assert mesh_data.shape_keys is not None, "Mesh object should have shape keys"
+
+    shape_key_names = (
+        'MORPH_BASE',
+        'pickaxe',
+        'axe',
+        'Blob_03',
+        'Blob02',
+        'Blob01',
+    )
+    shape_keys = mesh_data.shape_keys.key_blocks
+    assert len(shape_keys) == 6, "Mesh object should have 6 shape keys"
+    for i, shape_key in enumerate(shape_keys):
+        expected_value = 1.0 if i == 0 else 0.0
+        assert shape_key.value == expected_value, f"Shape key {shape_key.name} should have a value of {expected_value} (found {shape_key.value})"
+        assert shape_key.name == shape_key_names[i], f"Shape key {i} name should be named {shape_key_names[i]}"
+
+
+def test_psk_import_without_shape_keys():
+    assert bpy.ops.psk.import_file(
+        filepath=SLURP_MONSTER_AXE_FILEPATH,
+        components='MESH',
+        should_import_shape_keys=False,
+        ) == {'FINISHED'}
+
+    mesh_object = bpy.data.objects.get('Slurp_Monster_Axe_LOD0', None)
+    assert mesh_object is not None, "Mesh object not found in the scene"
+    assert mesh_object.type == 'MESH', "Mesh object type should be MESH"
+
+    mesh_data = typing_cast(Mesh, mesh_object.data)
+    assert mesh_data is not None, "Mesh data should not be None"
+    assert mesh_data.shape_keys is None, "Mesh object should not have shape keys"
+
+
+def test_psk_import_with_invalid_faces():
+    assert bpy.ops.psk.import_file(
+        filepath=BAT_FILEPATH,
+        components='MESH'
+        ) == {'FINISHED'}

tests/requirements.txt

@@ -0,0 +1,3 @@
+pytest
+pytest-cov
+psk-psa-py == 0.0.4

tests/test.sh

@@ -0,0 +1,8 @@
+# usr/bin/env bash
+# This file is meant to be executed from inside a Docker container.
+# To run tests on the host system, use the `test.sh` script in the root directory.
+export BLENDER_EXECUTABLE=$(cat /blender_executable_path)
+pytest --cov-report xml --cov=/root/.config/blender -svv tests --blender-executable $BLENDER_EXECUTABLE --blender-addons-dirs ../addons
+# Fixes the paths in the coverage report to be relative to the current directory.
+sed -i 's|/root/.config/blender||g' coverage.xml
+sed -i 's|5.0/scripts/addons/io_scene_psk_psa/||g' coverage.xml