Using Gitea-compatible upload-artifact action

.github/workflows/main.yml

@@ -16,11 +16,16 @@ jobs:
     env:
       ADDON_NAME: io_scene_psk_psa
     steps:
-      - uses: actions/checkout@v3
+      - uses: actions/checkout@v4
         with:
-          lfs: true
+          persist-credentials: true
       - name: Checkout LFS objects
-        run: git lfs checkout
+        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:
@@ -38,8 +43,7 @@ jobs:
           sudo apt-get install python3 -y
       - name: Install Requirements
         run: |
-          python3 -m pip install --upgrade pip
-          python3 -m pip install virtualenv
+          sudo apt-get install python3-virtualenv -y
           python3 -m virtualenv venv
           source venv/bin/activate
           pip install pytest-blender
@@ -69,7 +73,7 @@ jobs:
           source venv/bin/activate
           pytest -svv tests --blender-addons-dirs .
       - name: Archive addon
-        uses: actions/upload-artifact@v4
+        uses: https://github.com/christopherHX/gitea-upload-artifact@v4
         with:
           name: ${{ env.ADDON_NAME }}-${{ github.ref_name }}-${{ github.sha }}
           path: |

AGENTS.md

@@ -1,12 +0,0 @@
-# AGENTS.md
-
-This is an Blender addon for importing and exporting Unreal Engine PSK (skeletal mesh) and PSX (animation) files.
-
-# PSK/PSA File Format Notes
-* PSK and PSA bone hierarchies must have a single root bone. The root bone's `parent_index` is always `0`.
-* All indices in PSK/PSX files are zero-based.
-* All string fields in PSK/PSX files use Windows-1252 encoding and are null-terminated if they do not use the full length of the field.
-* Bone transforms are in parent bone space, except for root bones, which are in world space.
-
-# Naming Conventions
-* The `PSX` prefix is used when refer to concepts that are shared between PSK and PSX files.

README.md

@@ -13,37 +13,43 @@ For Blender 4.2 and higher, download the latest version from the [Blender Extens
 For Blender 4.1 and lower, see [Legacy Compatibility](#legacy-compatibility).
 
 # Features
-* Full PSK/PSA import and export capabilities.
-* Non-standard file section data (.pskx) is supported for import only (vertex normals, extra UV channels, vertex colors, shape keys).
+* [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.
-* [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).
 * 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.
-* Manual re-ordering of material slots.
-* Multiple armature objects can be exported to a single PSK or PSA file, allowing seamless use of [action slots](https://docs.blender.org/manual/en/latest/animation/actions.html#action-slots).
-* Support for exporting instance collections.
+* Compress exported sequences via resampling ratios or frame quotas.
 
 # Usage
-## 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`.
 
-## Importing a PSK/PSKX
+## 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`.
 
-## 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`.
-
-## Importing a PSA
+### 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

io_scene_psk_psa/__init__.py

@@ -1,35 +1,40 @@
-from bpy.app.handlers import persistent
-
-from .shared import types as shared_types, helpers as shared_helpers
-from .shared import dfs as shared_dfs, ui as shared_ui
-from .shared import operators as shared_operators
+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 import 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 .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
-from .psa.import_ import ui as psa_import_ui, properties as psa_import_properties
-
-from .psa import file_handlers as psa_file_handlers
+from .psa.import_ import (
+    operators as psa_import_operators,
+    ui as psa_import_ui,
+    properties as psa_import_properties,
+)
 
 _needs_reload = 'bpy' in locals()
 
@@ -108,7 +113,6 @@ def register():
     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'}))
@@ -124,7 +128,6 @@ def unregister():
     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)
@@ -135,16 +138,3 @@ def unregister():
 
 if __name__ == '__main__':
     register()
-
-
-@persistent
-def load_handler(dummy):
-    # Convert old `psa_sequence_fps` property to new `psa_export.fps` property.
-    # This is only needed for backwards compatibility with files that may have used older versions of the addon.
-    for action in bpy.data.actions:
-        if 'psa_sequence_fps' in action:
-            action.psa_export.fps = action['psa_sequence_fps']
-            del action['psa_sequence_fps']
-
-
-bpy.app.handlers.load_post.append(load_handler)

io_scene_psk_psa/blender_manifest.toml

@@ -1,6 +1,6 @@
 schema_version = "1.0.0"
 id = "io_scene_psk_psa"
-version = "9.1.0"
+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>"

io_scene_psk_psa/psa/builder.py

@@ -39,7 +39,6 @@ class PsaBuildOptions:
         self.export_space = 'WORLD'
         self.forward_axis = 'X'
         self.up_axis = 'Z'
-        self.root_bone_name = 'ROOT'
         self.sequence_source = 'ACTIONS'  # One of ('ACTIONS', 'TIMELINE_MARKERS', 'NLA_STRIPS')
     
     @property
@@ -162,7 +161,6 @@ def build_psa(context: Context, options: PsaBuildOptions) -> Psa:
     psx_bone_create_result = create_psx_bones(
         armature_objects=armature_objects_for_bones,
         export_space=options.export_space,
-        root_bone_name=options.root_bone_name,
         forward_axis=options.forward_axis,
         up_axis=options.up_axis,
         scale=options.scale,

io_scene_psk_psa/psa/export/operators.py

@@ -346,14 +346,6 @@ class PSA_OT_export_collection(Operator, ExportHelper, PsaExportMixin):
                 op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_DEHLT')
                 op.is_selected = False
 
-            advanced_bones_header, advanced_bones_panel = bones_panel.panel('Advanced', default_closed=True)
-            advanced_bones_header.label(text='Advanced')
-            if advanced_bones_panel:
-                flow = advanced_bones_panel.grid_flow(row_major=True)
-                flow.use_property_split = True
-                flow.use_property_decorate = False
-                flow.prop(self, 'root_bone_name')
-
         # Transform
         transform_header, transform_panel = layout.panel('Transform', default_closed=False)
         transform_header.label(text='Transform', icon='DRIVER_TRANSFORM')
@@ -565,7 +557,6 @@ def create_psa_export_options(context: Context, armature_objects: Sequence[Objec
     options.scale = pg.scale
     options.forward_axis = pg.forward_axis
     options.up_axis = pg.up_axis
-    options.root_bone_name = pg.root_bone_name
     options.sequence_source = pg.sequence_source
 
     return options
@@ -626,14 +617,6 @@ class PSA_OT_export(Operator, ExportHelper):
                     rows=rows
                     )
 
-            bones_advanced_header, bones_advanced_panel = bones_panel.panel('Bones Advanced', default_closed=True)
-            bones_advanced_header.label(text='Advanced')
-            if bones_advanced_panel:
-                flow = bones_advanced_panel.grid_flow()
-                flow.use_property_split = True
-                flow.use_property_decorate = False
-                flow.prop(pg, 'root_bone_name', text='Root Bone Name')
-
         # TRANSFORM
         transform_header, transform_panel = layout.panel('Advanced', default_closed=False)
         transform_header.label(text='Transform', icon='DRIVER_TRANSFORM')

io_scene_psk_psa/psk/builder.py

@@ -1,10 +1,10 @@
 import bmesh
 import bpy
 import numpy as np
-from bpy.types import Armature, Context, Object, Mesh, Material
-from mathutils import Matrix
-from typing import Iterable, Sequence, cast as typing_cast
-from psk_psa_py.shared.data import Vector3
+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 (
@@ -12,6 +12,7 @@ from ..shared.helpers import (
     ObjectTree,
     PskInputObjects,
     PsxBoneCollection,
+    convert_bpy_quaternion_to_psx_quaternion,
     convert_string_to_cp1252_bytes,
     create_psx_bones,
     get_armature_for_mesh_object,
@@ -31,7 +32,6 @@ class PskBuildOptions(object):
         self.export_space = 'WORLD'
         self.forward_axis = 'X'
         self.up_axis = 'Z'
-        self.root_bone_name = 'ROOT'
 
 
 class PskBuildResult(object):
@@ -99,13 +99,20 @@ def build_psk(context: Context, input_objects: PskInputObjects, options: PskBuil
         forward_axis=options.forward_axis,
         up_axis=options.up_axis,
         scale=options.scale,
-        root_bone_name=options.root_bone_name,
         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]
     
@@ -311,18 +318,17 @@ def build_psk(context: Context, input_objects: PskInputObjects, options: PskBuil
         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()
-            face.material_index = material_indices[f.material_index]
-            face.wedge_indices[0] = loop_wedge_indices[f.loops[2]]
-            face.wedge_indices[1] = loop_wedge_indices[f.loops[1]]
-            face.wedge_indices[2] = loop_wedge_indices[f.loops[0]]
-            face.smoothing_groups = poly_groups[f.polygon_index]
+            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[0], face.wedge_indices[2] = face.wedge_indices[2], face.wedge_indices[0]
+                face.wedge_indices = (face.wedge_indices[2], face.wedge_indices[1], face.wedge_indices[0])
 
         # Weights
         if armature_object is not None:

io_scene_psk_psa/psk/export/operators.py

@@ -207,7 +207,6 @@ def get_psk_build_options_from_property_group(scene: Scene, pg: PskExportMixin)
     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.root_bone_name = pg.root_bone_name
     options.material_order_mode = pg.material_order_mode
     options.material_name_list = [x.material_name for x in pg.material_name_list]
     
@@ -309,14 +308,6 @@ class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
                 op = col.operator(PSK_OT_bone_collection_list_select_all.bl_idname, text='', icon='CHECKBOX_DEHLT')
                 op.is_selected = False
 
-            advanced_bones_header, advanced_bones_panel = bones_panel.panel('Advanced', default_closed=True)
-            advanced_bones_header.label(text='Advanced')
-            if advanced_bones_panel:
-                flow = advanced_bones_panel.grid_flow(row_major=True)
-                flow.use_property_split = True
-                flow.use_property_decorate = False
-                flow.prop(self, 'root_bone_name')
-
         # Materials
         materials_header, materials_panel = layout.panel('Materials', default_closed=False)
         materials_header.label(text='Materials', icon='MATERIAL')
@@ -429,13 +420,6 @@ class PSK_OT_export(Operator, ExportHelper):
                 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)
-            bones_advanced_header, bones_advanced_panel = bones_panel.panel('Advanced', default_closed=True)
-            bones_advanced_header.label(text='Advanced')
-            if bones_advanced_panel:
-                flow = bones_advanced_panel.grid_flow(row_major=True)
-                flow.use_property_split = True
-                flow.use_property_decorate = False
-                flow.prop(pg, 'root_bone_name')
 
         # Materials
         materials_header, materials_panel = layout.panel('Materials', default_closed=False)

io_scene_psk_psa/psk/export/properties.py

@@ -3,10 +3,9 @@ from bpy.props import (
     CollectionProperty,
     EnumProperty,
     IntProperty,
-    PointerProperty,
     StringProperty,
 )
-from bpy.types import Material, PropertyGroup
+from bpy.types import PropertyGroup
 
 from ...shared.types import ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin
 

io_scene_psk_psa/psk/export/properties.pyi

@@ -1,5 +1,3 @@
-from bpy.types import Material
-
 from ...shared.types import BpyCollectionProperty, ExportSpaceMixin, TransformMixin, PsxBoneExportMixin, TransformSourceMixin
 
 

io_scene_psk_psa/shared/helpers.py

@@ -332,7 +332,6 @@ class ObjectTree:
 def create_psx_bones(
         armature_objects: list[Object],
         export_space: str = 'WORLD',
-        root_bone_name: str = 'ROOT',
         forward_axis: str = 'X',
         up_axis: str = 'Z',
         scale: float = 1.0,
@@ -351,9 +350,12 @@ def create_psx_bones(
     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(
-            'Multiple root armature objects were found. '
-            'Only one root armature object is allowed. '
+            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.'
         )
 
@@ -453,6 +455,14 @@ def create_psx_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.
@@ -517,13 +527,10 @@ def create_psx_bones(
     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:
-            error_message = f'Found {count} bones with the name "{bone_name}". '
+            raise RuntimeError(
+                f'Found {count} bones with the name "{bone_name}". '
                 f'Bone names must be unique when compared case-insensitively.'
-
-            if len(armature_objects) > 1 and bone_name == root_bone_name.upper():
-                error_message += f' This is the name of the automatically generated root bone. Consider changing this '
-                f''
-                raise RuntimeError(error_message)
+            )
     
     # Apply the scale to the bone locations.
     for bone in bones:

io_scene_psk_psa/shared/types.py

@@ -179,11 +179,6 @@ class PsxBoneExportMixin:
     )
     bone_collection_list: CollectionProperty(type=PSX_PG_bone_collection_list_item)
     bone_collection_list_index: IntProperty(default=0, name='', description='')
-    root_bone_name: StringProperty(
-        name='Root Bone Name',
-        description='The name of the root bone when exporting a PSK with either no armature or multiple armatures',
-        default='ROOT',
-    )
 
 
 class PSX_PG_scene_export(PropertyGroup, TransformMixin):

io_scene_psk_psa/shared/types.pyi

@@ -54,7 +54,6 @@ class PsxBoneExportMixin:
     bone_filter_mode: str
     bone_collection_list: BpyCollectionProperty[PSX_PG_bone_collection_list_item]
     bone_collection_list_index: int
-    root_bone_name: str
 
 
 class PSX_PG_scene_export(TransformSourceMixin):

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}."