Loads of changes

* Now asserting instead of throwing exceptions in some cases where we
don't want to fail gracefully
* Added "export space" option for PSA & PSK exports.
* Removed "Root Motion" option in PSA export, replace with a "Root"
  export space.
* Added support for exporting multiple armatures to a PSK (only works
  for collection exporter atm)
* More graceful error handling for IO errors (i.e., writing to a
   for which the user doesn't have permission)
* Proper handling for slotted actions.

io_scene_psk_psa/psa/builder.py

@@ -1,5 +1,3 @@
-from typing import Optional
-
 from bpy.types import Bone, Action, PoseBone
 
 from .data import *
@@ -31,7 +29,6 @@ class PsaBuildOptions:
         self.bone_collection_indices: List[int] = []
         self.sequence_name_prefix: str = ''
         self.sequence_name_suffix: str = ''
-        self.root_motion: bool = False
         self.scale = 1.0
         self.sampling_mode: str = 'INTERPOLATED'  # One of ('INTERPOLATED', 'SUBFRAME')
         self.export_space = 'WORLD'
@@ -39,18 +36,29 @@ class PsaBuildOptions:
         self.up_axis = 'Z'
 
 
-def _get_pose_bone_location_and_rotation(pose_bone: PoseBone, armature_object: Object, root_motion: bool, scale: float, coordinate_system_transform: Matrix) -> Tuple[Vector, Quaternion]:
+def _get_pose_bone_location_and_rotation(
+        pose_bone: PoseBone,
+        armature_object: Object,
+        export_space: str,
+        scale: Vector,
+        coordinate_system_transform: Matrix) -> Tuple[Vector, Quaternion]:
     if pose_bone.parent is not None:
         pose_bone_matrix = pose_bone.matrix
         pose_bone_parent_matrix = pose_bone.parent.matrix
         pose_bone_matrix = pose_bone_parent_matrix.inverted() @ pose_bone_matrix
     else:
-        if root_motion:
-            # Get the bone's pose matrix, taking the armature object's world matrix into account.
-            pose_bone_matrix = armature_object.matrix_world @ pose_bone.matrix
-        else:
-            # Use the bind pose matrix for the 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.
+        # TODO: taking the pose bone matrix puts this in armature space.
+        pose_bone_matrix = Matrix.Identity(4)
+        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)
 
         # 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.
@@ -73,6 +81,8 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
     psa = Psa()
 
     armature_object = active_object
+    evaluated_armature_object = armature_object.evaluated_get(context.evaluated_depsgraph_get())
+
     armature_data = typing.cast(Armature, armature_object.data)
     bones: List[Bone] = list(iter(armature_data.bones))
 
@@ -94,17 +104,21 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
 
     # The bone building code should be shared between the PSK and PSA exporters, since they both need to build a nearly identical bone list.
 
+    # TODO: The PSA bones are just here to validate the hierarchy. The pose information is not used by the engine.
     # Build list of PSA bones.
     psa.bones = convert_blender_bones_to_psx_bones(
         bones=bones,
         bone_class=Psa.Bone,
         export_space=options.export_space,
-        armature_object_matrix_world=armature_object.matrix_world,
+        armature_object_matrix_world=armature_object.matrix_world,  # evaluated_armature_object.matrix_world,
         scale=options.scale,
         forward_axis=options.forward_axis,
         up_axis=options.up_axis
     )
 
+    # We invert the export space matrix so that we neutralize the transform of the armature object.
+    export_space_matrix_inverse = get_export_space_matrix(options.export_space, armature_object)
+
     # 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}'
@@ -124,7 +138,7 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
 
     for export_sequence_index, export_sequence in enumerate(options.sequences):
         # Look up the pose bones for the bones that are going to be exported.
-        pose_bones = [(bone_names.index(bone.name), bone) for bone in export_sequence.armature_object.pose.bones]
+        pose_bones = [(bone_names.index(bone.name), bone) for bone in armature_object.pose.bones]
         pose_bones.sort(key=lambda x: x[0])
         pose_bones = [x[1] for x in pose_bones]
         pose_bones = [pose_bones[bone_index] for bone_index in bone_indices]
@@ -178,6 +192,13 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
             key.time = 1.0 / psa_sequence.fps
             psa.keys.append(key)
 
+        # TODO: In _get_pose_bone_location_and_rotation, we need to factor in the evaluated armature object's scale.
+        #  Then also, if we're in ARMATURE export space, invert the pose bone matrix so that it's the identity matrix.
+
+        # TODO: extract the scale out of the evaluated_armature_object.matrix_world.
+        _, _, scale = evaluated_armature_object.matrix_world.decompose()
+        scale *= options.scale
+
         match options.sampling_mode:
             case 'INTERPOLATED':
                 # Used as a store for the last frame's pose bone locations and rotations.
@@ -203,9 +224,9 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
                             for pose_bone in pose_bones:
                                 location, rotation = _get_pose_bone_location_and_rotation(
                                     pose_bone,
-                                    export_sequence.armature_object,
-                                    root_motion=options.root_motion,
-                                    scale=options.scale,
+                                    armature_object,
+                                    options.export_space,
+                                    scale,
                                     coordinate_system_transform=coordinate_system_transform
                                 )
                                 last_frame_bone_poses.append((location, rotation))
@@ -225,9 +246,9 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
                             for pose_bone in pose_bones:
                                 location, rotation = _get_pose_bone_location_and_rotation(
                                     pose_bone,
-                                    export_sequence.armature_object,
-                                    root_motion=options.root_motion,
-                                    scale=options.scale,
+                                    armature_object,
+                                    options.export_space,
+                                    scale,
                                     coordinate_system_transform=coordinate_system_transform
                                 )
                                 next_frame_bone_poses.append((location, rotation))
@@ -249,7 +270,13 @@ def build_psa(context: bpy.types.Context, options: PsaBuildOptions) -> Psa:
                     context.scene.frame_set(frame=int(frame), subframe=frame % 1.0)
 
                     for pose_bone in pose_bones:
-                        location, rotation = _get_pose_bone_location_and_rotation(pose_bone, export_sequence.armature_object, options)
+                        location, rotation = _get_pose_bone_location_and_rotation(
+                            pose_bone,
+                            armature_object,
+                            options.export_space,
+                            scale,
+                            coordinate_system_transform=coordinate_system_transform
+                        )
                         add_key(location, rotation)
 
                     frame += frame_step

io_scene_psk_psa/psa/export/operators.py

@@ -27,7 +27,7 @@ def get_sequences_propnames_from_source(sequence_source: str) -> Optional[Tuple[
         case 'ACTIVE_ACTION':
             return 'active_action_list', 'active_action_list_index'
         case _:
-            raise ValueError(f'Unhandled sequence source: {sequence_source}')
+            assert False, f'Invalid sequence source: {sequence_source}'
 
 
 def is_action_for_object(obj: Object, action: Action):
@@ -84,7 +84,6 @@ def update_actions_and_timeline_markers(context: Context):
             continue
 
         for (name, frame_start, frame_end) in get_sequences_from_action(action):
-            print(name)
             item = pg.action_list.add()
             item.action = action
             item.name = name
@@ -151,18 +150,18 @@ def get_sequence_fps(context: Context, fps_source: str, fps_custom: float, actio
             # Get the minimum value of action metadata FPS values.
             return min([action.psa_export.fps for action in actions])
         case _:
-            raise RuntimeError(f'Invalid FPS source "{fps_source}"')
+            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([action.psa_export.compression_ratio for action in actions])
+            return min(map(lambda action: action.psa_export.compression_ratio, actions))
         case 'CUSTOM':
             return compression_ratio_custom
         case _:
-            raise RuntimeError(f'Invalid compression ratio source "{compression_ratio_source}"')
+            assert False, f'Invalid compression ratio source: {compression_ratio_source}'
 
 
 def get_animation_data_object(context: Context) -> Object:
@@ -389,7 +388,6 @@ class PSA_OT_export(Operator, ExportHelper):
             flow = transform_panel.grid_flow(row_major=True)
             flow.use_property_split = True
             flow.use_property_decorate = False
-            flow.prop(pg, 'root_motion')
             flow.prop(pg, 'export_space')
             flow.prop(pg, 'scale')
             flow.prop(pg, 'forward_axis')
@@ -506,7 +504,7 @@ class PSA_OT_export(Operator, ExportHelper):
                     export_sequence.key_quota = action.psa_export.key_quota
                     export_sequences.append(export_sequence)
             case _:
-                raise ValueError(f'Unhandled sequence source: {pg.sequence_source}')
+                assert False, f'Invalid sequence source: {pg.sequence_source}'
 
         if len(export_sequences) == 0:
             self.report({'ERROR'}, 'No sequences were selected for export')
@@ -516,10 +514,9 @@ class PSA_OT_export(Operator, ExportHelper):
         options.animation_data = animation_data
         options.sequences = export_sequences
         options.bone_filter_mode = pg.bone_filter_mode
-        options.bone_collection_indices = [x.index for x in pg.bone_collection_list if x.is_selected]
+        options.bone_collection_indices = [(x.armature_object_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.root_motion = pg.root_motion
         options.scale = pg.scale
         options.sampling_mode = pg.sampling_mode
         options.export_space = pg.export_space

io_scene_psk_psa/psa/export/properties.py

@@ -103,14 +103,6 @@ def animation_data_override_update_cb(self: 'PSA_PG_export', context: Context):
 
 
 class PSA_PG_export(PropertyGroup, ForwardUpAxisMixin, ExportSpaceMixin):
-    root_motion: BoolProperty(
-        name='Root Motion',
-        options=empty_set,
-        default=False,
-        description='When enabled, the root bone will be transformed as it appears in the scene.\n\n'
-                    'You might want to disable this if you are exporting an animation for an armature that is '
-                    'attached to another object, such as a weapon or a shield',
-    )
     should_override_animation_data: BoolProperty(
         name='Override Animation Data',
         options=empty_set,

io_scene_psk_psa/psa/export/ui.py

@@ -23,14 +23,14 @@ class PSA_UL_export_sequences(UIList):
 
         row = layout.row(align=True)
         row.alignment = 'RIGHT'
-        if item.frame_end < item.frame_start:
-            row.label(text='', icon='FRAME_PREV')
-        if is_pose_marker:
-            row.label(text=item.action.name, icon='PMARKER')
+
+        row.label(text=str(abs(item.frame_end - item.frame_start) + 1), icon='FRAME_PREV' if item.frame_end < item.frame_start else 'KEYFRAME')
 
         if hasattr(item, 'armature_object') and 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()

io_scene_psk_psa/psa/import_/properties.py

@@ -93,7 +93,7 @@ class PsaImportMixin:
         soft_max=60.0,
         step=100,
     )
-    compression_ratio_source: EnumProperty(name='Compression Ratio Source', items=compression_ratio_source_items)
+    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',

io_scene_psk_psa/psa/importer.py

@@ -260,7 +260,7 @@ def import_psa(context: Context, psa_reader: PsaReader, armature_object: Object,
             case 'SEQUENCE':
                 target_fps = sequence.fps
             case _:
-                raise ValueError(f'Unknown FPS source: {options.fps_source}')
+                assert False, f'Invalid FPS source: {options.fps_source}'
 
         if options.should_write_keyframes:
             # Remove existing f-curves.

io_scene_psk_psa/psk/builder.py

@@ -1,32 +1,36 @@
 import typing
-from typing import Optional
+from collections import Counter
+from typing import Dict, Generator, Set, Iterable, Optional, cast
 
 import bmesh
+import bpy
 import numpy as np
-from bpy.types import Material, Collection, Context
+from bpy.types import Material, Collection, Context, Object, Armature, Bone
 
 from .data import *
 from .properties import triangle_type_and_bit_flags_to_poly_flags
 from ..shared.dfs import dfs_collection_objects, dfs_view_layer_objects, DfsObject
-from ..shared.helpers import *
+from ..shared.helpers import get_coordinate_system_transform, convert_string_to_cp1252_bytes, \
+    get_export_bone_names, convert_blender_bones_to_psx_bones
 
 
 class PskInputObjects(object):
     def __init__(self):
         self.mesh_objects: List[DfsObject] = []
-        self.armature_object: Optional[Object] = None
+        self.armature_objects: Set[Object] = set()
 
 
 class PskBuildOptions(object):
     def __init__(self):
         self.bone_filter_mode = 'ALL'
-        self.bone_collection_indices: List[int] = []
+        self.bone_collection_indices: List[Tuple[str, int]] = []
         self.object_eval_state = 'EVALUATED'
         self.materials: List[Material] = []
         self.scale = 1.0
         self.export_space = 'WORLD'
         self.forward_axis = 'X'
         self.up_axis = 'Z'
+        self.root_bone_name = 'ROOT'
 
 
 def get_mesh_objects_for_collection(collection: Collection) -> Iterable[DfsObject]:
@@ -39,26 +43,24 @@ def get_mesh_objects_for_context(context: Context) -> Iterable[DfsObject]:
             yield dfs_object
 
 
-def get_armature_for_mesh_objects(mesh_objects: Iterable[Object]) -> Optional[Object]:
+def get_armature_for_mesh_object(mesh_object: Object) -> Optional[Object]:
+    for modifier in mesh_object.modifiers:
+        if modifier.type == 'ARMATURE':
+            return modifier.object
+    return None
+
+
+def get_armatures_for_mesh_objects(mesh_objects: Iterable[Object]) -> Generator[Object, None, None]:
     # Ensure that there are either no armature modifiers (static mesh) or that there is exactly one armature modifier
     # object shared between all meshes.
-    armature_modifier_objects = set()
+    armature_objects = set()
     for mesh_object in mesh_objects:
         modifiers = [x for x in mesh_object.modifiers if x.type == 'ARMATURE']
         if len(modifiers) == 0:
             continue
-        elif len(modifiers) > 1:
-            raise RuntimeError(f'Mesh "{mesh_object.name}" must have only one armature modifier')
-        armature_modifier_objects.add(modifiers[0].object)
-
-    if len(armature_modifier_objects) > 1:
-        armature_modifier_names = [x.name for x in armature_modifier_objects]
-        raise RuntimeError(
-            f'All meshes must have the same armature modifier, encountered {len(armature_modifier_names)} ({", ".join(armature_modifier_names)})')
-    elif len(armature_modifier_objects) == 1:
-        return list(armature_modifier_objects)[0]
-    else:
-        return None
+        if modifiers[0].object in armature_objects:
+            continue
+        yield modifiers[0].object
 
 
 def _get_psk_input_objects(mesh_objects: Iterable[DfsObject]) -> PskInputObjects:
@@ -68,7 +70,7 @@ def _get_psk_input_objects(mesh_objects: Iterable[DfsObject]) -> PskInputObjects
 
     input_objects = PskInputObjects()
     input_objects.mesh_objects = mesh_objects
-    input_objects.armature_object = get_armature_for_mesh_objects([x.obj for x in mesh_objects])
+    input_objects.armature_objects |= set(get_armatures_for_mesh_objects(map(lambda x: x.obj, mesh_objects)))
 
     return input_objects
 
@@ -91,97 +93,32 @@ class PskBuildResult(object):
         self.warnings: List[str] = []
 
 
-def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions) -> PskBuildResult:
-    armature_object: bpy.types.Object = input_objects.armature_object
+def _get_mesh_export_space_matrix(armature_objects: Iterable[Object], export_space: str) -> Matrix:
+    if not armature_objects:
+        return Matrix.Identity(4)
 
-    result = PskBuildResult()
-    psk = Psk()
-    bones = []
+    def get_object_space_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()
 
-    def get_export_space_matrix():
-        match options.export_space:
+
+    match export_space:
         case 'WORLD':
             return Matrix.Identity(4)
         case 'ARMATURE':
-                if armature_object is not None:
-                    return armature_object.matrix_world.inverted()
-                else:
-                    return Matrix.Identity(4)
+            return get_object_space_space_matrix(armature_objects[0]).inverted()
+        case 'ROOT':
+            # TODO: multiply this by the root bone's local matrix
+            armature_object = armature_objects[0]
+            armature_data = cast(armature_object.data, Armature)
+            armature_space_matrix = get_object_space_space_matrix(armature_object) @ armature_data.bones[0].matrix_local
+            return armature_space_matrix.inverted()
         case _:
-                raise ValueError(f'Invalid export space: {options.export_space}')
+            assert False, f'Invalid export space: {export_space}'
 
-    coordinate_system_matrix = get_coordinate_system_transform(options.forward_axis, options.up_axis)
-    coordinate_system_default_rotation = coordinate_system_matrix.to_quaternion()
 
-    export_space_matrix = get_export_space_matrix()  # TODO: maybe neutralize the scale here?
-    scale_matrix = Matrix.Scale(options.scale, 4)
-
-    # We effectively need 3 transforms, I think:
-    # 1. The transform for the mesh vertices.
-    # 2. The transform for the bone locations.
-    # 3. The transform for the bone rotations.
-
-    if armature_object is None or len(armature_object.data.bones) == 0:
-        # If the mesh has no armature object or no bones, simply assign it a dummy bone at the root to satisfy the
-        # requirement that a PSK file must have at least one bone.
-        psk_bone = Psk.Bone()
-        psk_bone.name = bytes('root', encoding='windows-1252')
-        psk_bone.flags = 0
-        psk_bone.children_count = 0
-        psk_bone.parent_index = 0
-        psk_bone.location = Vector3.zero()
-        psk_bone.rotation = Quaternion.from_bpy_quaternion(coordinate_system_default_rotation)
-        psk.bones.append(psk_bone)
-    else:
-        bone_names = get_export_bone_names(armature_object, options.bone_filter_mode, options.bone_collection_indices)
-        armature_data = typing.cast(Armature, armature_object.data)
-        bones = [armature_data.bones[bone_name] for bone_name in bone_names]
-
-        psk.bones = convert_blender_bones_to_psx_bones(
-            bones, Psk.Bone,
-            options.export_space,
-            armature_object.matrix_world,
-            options.scale,
-            options.forward_axis,
-            options.up_axis
-        )
-
-    # MATERIALS
-    for material in options.materials:
-        psk_material = Psk.Material()
-        try:
-            psk_material.name = bytes(material.name, encoding='windows-1252')
-        except UnicodeEncodeError:
-            raise RuntimeError(f'Material name "{material.name}" contains characters that cannot be encoded in the Windows-1252 codepage')
-        psk_material.texture_index = len(psk.materials)
-        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)
-
-    # TODO: This wasn't left in a good state. We should detect if we need to add a "default" material.
-    #  This can be done by checking if there is an empty material slot on any of the mesh objects, or if there are
-    #  no material slots on any of the mesh objects.
-    #  If so, it should be added to the end of the list of materials, and its index should mapped to a None value in the
-    #  material indices list.
-    if len(psk.materials) == 0:
-        # Add a default material if no materials are present.
-        psk_material = Psk.Material()
-        psk_material.name = bytes('None', encoding='windows-1252')
-        psk.materials.append(psk_material)
-
-    context.window_manager.progress_begin(0, len(input_objects.mesh_objects))
-
-    material_names = [m.name for m in options.materials]
-
-    vertex_transform_matrix = scale_matrix @ coordinate_system_matrix @ export_space_matrix
-
-    for object_index, input_mesh_object in enumerate(input_objects.mesh_objects):
-
-        obj, instance_objects, matrix_world = input_mesh_object.obj, input_mesh_object.instance_objects, input_mesh_object.matrix_world
-
-        should_flip_normals = False
-
-        def get_material_name_indices(obj: Object, material_names: List[str]) -> Iterable[int]:
+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, the index 0 is returned.
@@ -195,70 +132,198 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
             except ValueError:
                 yield 0
 
-        # MATERIALS
-        material_indices = list(get_material_name_indices(obj, material_names))
+
+def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions) -> PskBuildResult:
+    armature_objects = list(input_objects.armature_objects)
+
+    result = PskBuildResult()
+    psk = Psk()
+    bones: List[Bone] = []
+
+    if options.export_space != 'WORLD' and len(armature_objects) > 1:
+        raise RuntimeError('When exporting multiple armatures, the Export Space must be World')
+
+    coordinate_system_matrix = get_coordinate_system_transform(options.forward_axis, options.up_axis)
+    coordinate_system_default_rotation = coordinate_system_matrix.to_quaternion()
+
+    scale_matrix = Matrix.Scale(options.scale, 4)
+
+    total_bone_count = sum(len(armature_object.data.bones) for armature_object in armature_objects)
+
+    # 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()
+
+    # 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:
+        bone_collection_indices = [x[1] for x in options.bone_collection_indices if x[0] == armature_object.name]
+        bone_names = get_export_bone_names(armature_object, options.bone_filter_mode, bone_collection_indices)
+        armature_object_bone_names[armature_object] = bone_names
+
+    if len(armature_objects) == 0 or total_bone_count == 0:
+        # If the mesh has no armature object or no bones, simply assign it a dummy bone at the root to satisfy the
+        # requirement that a PSK file must have at least one bone.
+        psk_bone = Psk.Bone()
+        psk_bone.name = convert_string_to_cp1252_bytes(options.root_bone_name)
+        psk_bone.flags = 0
+        psk_bone.children_count = 0
+        psk_bone.parent_index = 0
+        psk_bone.location = Vector3.zero()
+        psk_bone.rotation = Quaternion.from_bpy_quaternion(coordinate_system_default_rotation)
+        psk.bones.append(psk_bone)
+
+        armature_object_root_bone_indices[None] = 0
+    else:
+        # If we have multiple armature objects, create a root bone at the world origin.
+        if len(armature_objects) > 1:
+            psk_bone = Psk.Bone()
+            psk_bone.name = convert_string_to_cp1252_bytes(options.root_bone_name)
+            psk_bone.flags = 0
+            psk_bone.children_count = total_bone_count
+            psk_bone.parent_index = 0
+            psk_bone.location = Vector3.zero()
+            psk_bone.rotation = Quaternion.from_bpy_quaternion(coordinate_system_default_rotation)
+            psk.bones.append(psk_bone)
+
+            armature_object_root_bone_indices[None] = 0
+
+        root_bone = psk.bones[0] if len(psk.bones) > 0 else None
+
+        for armature_object in armature_objects:
+            bone_names = armature_object_bone_names[armature_object]
+            armature_data = typing.cast(Armature, armature_object.data)
+            bones = [armature_data.bones[bone_name] for bone_name in bone_names]
+
+            psk_bones = convert_blender_bones_to_psx_bones(
+                bones=bones,
+                bone_class=Psk.Bone,
+                export_space=options.export_space,
+                armature_object_matrix_world=armature_object.matrix_world,
+                scale=options.scale,
+                forward_axis=options.forward_axis,
+                up_axis=options.up_axis,
+                root_bone=root_bone,
+            )
+
+            # If we are appending these bones to an existing list of bones, we need to adjust the parent indices.
+            if len(psk.bones) > 0:
+                parent_index_offset = len(psk.bones)
+                for bone in psk_bones[1:]:
+                    bone.parent_index += parent_index_offset
+
+            armature_object_root_bone_indices[armature_object] = len(psk.bones)
+
+            psk.bones.extend(psk_bones)
+
+    # Check if there are bone name conflicts between armatures.
+    bone_name_counts = Counter(x.name.decode('windows-1252').upper() for x in psk.bones)
+
+    for bone_name, count in bone_name_counts.items():
+        if count > 1:
+            raise RuntimeError(f'Found {count} bones with the name "{bone_name}". Bone names must be unique when compared case-insensitively.')
+
+    # Materials
+    for material in options.materials:
+        psk_material = Psk.Material()
+        psk_material.name = convert_string_to_cp1252_bytes(material.name)
+        psk_material.texture_index = len(psk.materials)
+        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)
+
+    # TODO: This wasn't left in a good state. We should detect if we need to add a "default" material.
+    #  This can be done by checking if there is an empty material slot on any of the mesh objects, or if there are
+    #  no material slots on any of the mesh objects.
+    #  If so, it should be added to the end of the list of materials, and its index should mapped to a None value in the
+    #  material indices list.
+    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_objects))
+
+    mesh_export_space_matrix = _get_mesh_export_space_matrix(armature_objects, options.export_space)
+    vertex_transform_matrix = scale_matrix @ coordinate_system_matrix @ mesh_export_space_matrix
+
+    original_armature_object_pose_positions = {armature_object: armature_object.data.pose_position for armature_object in armature_objects}
+
+    # Temporarily force the armature into the rest position.
+    # We will undo this later.
+    for armature_object in armature_objects:
+        armature_object.data.pose_position = 'REST'
+
+    material_names = [m.name for m in options.materials]
+
+    for object_index, input_mesh_object in enumerate(input_objects.mesh_objects):
+        obj, instance_objects, matrix_world = input_mesh_object.obj, input_mesh_object.instance_objects, 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:
             # Add a default material if no materials are present.
             material_indices = [0]
 
-        # MESH DATA
+        # 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 = obj.data
             case 'EVALUATED':
                 # Create a copy of the mesh object after non-armature modifiers are applied.
-
-                # Temporarily force the armature into the rest position.
-                # We will undo this later.
-                old_pose_position = None
-                if armature_object is not None:
-                    old_pose_position = armature_object.data.pose_position
-                    armature_object.data.pose_position = 'REST'
-
                 depsgraph = context.evaluated_depsgraph_get()
                 bm = bmesh.new()
 
                 try:
                     bm.from_object(obj, depsgraph)
-                except ValueError:
+                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.')
+                    'This is likely because the object is in a collection that has been excluded from the view layer.') from e
 
-                mesh_data = bpy.data.meshes.new('')
+                evaluated_mesh_data = bpy.data.meshes.new('')
+                mesh_data = evaluated_mesh_data
                 bm.to_mesh(mesh_data)
                 del bm
-                mesh_object = bpy.data.objects.new('', mesh_data)
+                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.
+                # 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.
+                # 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.
                 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)
-
-                # Restore the previous pose position on the armature.
-                if old_pose_position is not None:
-                    armature_object.data.pose_position = old_pose_position
             case _:
-                raise ValueError(f'Invalid object evaluation state: {options.object_eval_state}')
+                assert False, f'Invalid object evaluation state: {options.object_eval_state}'
 
         vertex_offset = len(psk.points)
         point_transform_matrix = vertex_transform_matrix @ mesh_object.matrix_world
 
-        # VERTICES
+        # Vertices
         for vertex in mesh_data.vertices:
             point = Vector3()
             v = point_transform_matrix @ vertex.co
@@ -269,7 +334,7 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
 
         uv_layer = mesh_data.uv_layers.active.data
 
-        # WEDGES
+        # Wedges
         mesh_data.calc_loop_triangles()
 
         # Build a list of non-unique wedges.
@@ -286,7 +351,7 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
             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
+        # 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):
@@ -299,7 +364,7 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
                 psk.wedges.append(wedge)
                 loop_wedge_indices[loop_index] = wedge_index
 
-        # FACES
+        # 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:
@@ -316,17 +381,19 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
             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]
 
-        # WEIGHTS
+        # Weights
         if armature_object is not None:
             armature_data = typing.cast(Armature, armature_object.data)
+            bone_index_offset = 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 = [x.name for x in bones]
+
+            bone_names = armature_object_bone_names[armature_object]
             vertex_group_names = [x.name for x in mesh_object.vertex_groups]
-            vertex_group_bone_indices = dict()
+            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)
+                    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.
@@ -336,8 +403,7 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
                         bone = armature_data.bones[vertex_group_name]
                         while bone is not None:
                             try:
-                                bone_index = bone_names.index(bone.name)
-                                vertex_group_bone_indices[vertex_group_index] = bone_index
+                                vertex_group_bone_indices[vertex_group_index] = bone_names.index(bone.name) + bone_index_offset
                                 break
                             except ValueError:
                                 bone = bone.parent
@@ -366,22 +432,30 @@ def build_psk(context, input_objects: PskInputObjects, options: PskBuildOptions)
                     psk.weights.append(w)
                     vertices_assigned_weights[vertex_index] = True
 
-            # Assign vertices that have not been assigned weights to the root bone.
+            # Assign vertices that have not been assigned weights to the root bone of the armature.
+            fallback_weight_bone_index = 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 = 0
+                    w.bone_index = fallback_weight_bone_index
                     w.point_index = vertex_offset + vertex_index
                     w.weight = 1.0
                     psk.weights.append(w)
 
-        if options.object_eval_state == 'EVALUATED':
+        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_object.data.pose_position = pose_position
+
     context.window_manager.progress_end()
 
     result.psk = psk

io_scene_psk_psa/psk/export/operators.py

@@ -1,3 +1,4 @@
+from pathlib import Path
 from typing import List, Optional, cast, Iterable
 
 import bpy
@@ -75,10 +76,10 @@ class PSK_OT_populate_bone_collection_list(Operator):
         except RuntimeError as e:
             self.report({'ERROR_INVALID_CONTEXT'}, str(e))
             return {'CANCELLED'}
-        if input_objects.armature_object is None:
-            self.report({'ERROR_INVALID_CONTEXT'}, 'No armature found in collection')
+        if not input_objects.armature_objects:
+            self.report({'ERROR_INVALID_CONTEXT'}, 'No armature modifiers found on mesh objects')
             return {'CANCELLED'}
-        populate_bone_collection_list(input_objects.armature_object, export_operator.bone_collection_list)
+        populate_bone_collection_list(input_objects.armature_objects, export_operator.bone_collection_list)
         return {'FINISHED'}
 
 
@@ -236,10 +237,11 @@ def get_psk_build_options_from_property_group(pg: 'PSK_PG_export') -> PskBuildOp
     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 = [x.index for x in pg.bone_collection_list if x.is_selected]
+    options.bone_collection_indices = [(x.armature_object_name, x.index) for x in pg.bone_collection_list if x.is_selected]
     options.scale = pg.scale
     options.forward_axis = pg.forward_axis
     options.up_axis = pg.up_axis
+    options.root_bone_name = pg.root_bone_name
 
     # TODO: perhaps move this into the build function and replace the materials list with a material names list.
     # materials = get_materials_for_mesh_objects(depsgraph, mesh_objects)
@@ -276,12 +278,13 @@ class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
             return {'CANCELLED'}
 
         options = get_psk_build_options_from_property_group(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(result.psk, self.filepath)
+            write_psk(result.psk, filepath)
             if len(result.warnings) > 0:
                 self.report({'WARNING'}, f'PSK export successful with {len(result.warnings)} warnings')
             else:
@@ -299,7 +302,7 @@ class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
         flow.use_property_split = True
         flow.use_property_decorate = False
 
-        # MESH
+        # Mesh
         mesh_header, mesh_panel = layout.panel('Mesh', default_closed=False)
         mesh_header.label(text='Mesh', icon='MESH_DATA')
         if mesh_panel:
@@ -309,17 +312,26 @@ class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
             flow.prop(self, 'object_eval_state', text='Data')
             flow.prop(self, 'should_exclude_hidden_meshes')
 
-        # BONES
+        # 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':
                 bones_panel.operator(PSK_OT_populate_bone_collection_list.bl_idname, icon='FILE_REFRESH')
                 rows = max(3, min(len(self.bone_collection_list), 10))
                 bones_panel.template_list('PSX_UL_bone_collection_list', '', self, 'bone_collection_list', self, 'bone_collection_list_index', rows=rows)
 
-        # MATERIALS
+            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')
 
@@ -334,7 +346,7 @@ class PSK_OT_export_collection(Operator, ExportHelper, PskExportMixin):
             col.separator()
             col.operator(PSK_OT_material_list_name_add.bl_idname, text='', icon='ADD')
 
-        # TRANSFORM
+        # Transform
         transform_header, transform_panel = layout.panel('Transform', default_closed=False)
         transform_header.label(text='Transform')
         if transform_panel:
@@ -368,13 +380,9 @@ class PSK_OT_export(Operator, ExportHelper):
             self.report({'ERROR_INVALID_CONTEXT'}, str(e))
             return {'CANCELLED'}
 
-        if len(input_objects.mesh_objects) == 0:
-            self.report({'ERROR_INVALID_CONTEXT'}, 'No mesh objects selected')
-            return {'CANCELLED'}
-
         pg = getattr(context.scene, 'psk_export')
 
-        populate_bone_collection_list(input_objects.armature_object, pg.bone_collection_list)
+        populate_bone_collection_list(input_objects.armature_objects, pg.bone_collection_list)
 
         depsgraph = context.evaluated_depsgraph_get()
 
@@ -393,7 +401,7 @@ class PSK_OT_export(Operator, ExportHelper):
 
         pg = getattr(context.scene, 'psk_export')
 
-        # MESH
+        # Mesh
         mesh_header, mesh_panel = layout.panel('Mesh', default_closed=False)
         mesh_header.label(text='Mesh', icon='MESH_DATA')
         if mesh_panel:
@@ -402,7 +410,7 @@ class PSK_OT_export(Operator, ExportHelper):
             flow.use_property_decorate = False
             flow.prop(pg, 'object_eval_state', text='Data')
 
-        # BONES
+        # Bones
         bones_header, bones_panel = layout.panel('Bones', default_closed=False)
         bones_header.label(text='Bones', icon='BONE_DATA')
         if bones_panel:
@@ -412,7 +420,7 @@ class PSK_OT_export(Operator, ExportHelper):
                 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
         materials_header, materials_panel = layout.panel('Materials', default_closed=False)
         materials_header.label(text='Materials', icon='MATERIAL')
         if materials_panel:
@@ -423,6 +431,18 @@ class PSK_OT_export(Operator, ExportHelper):
             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, 'scale')
+            flow.prop(pg, 'forward_axis')
+            flow.prop(pg, 'up_axis')
+
     def execute(self, context):
         pg = getattr(context.scene, 'psk_export')
 

io_scene_psk_psa/psk/export/properties.py

@@ -12,11 +12,6 @@ object_eval_state_items = (
     ('ORIGINAL', 'Original', 'Use data from original object with no modifiers applied'),
 )
 
-export_space_items = [
-    ('WORLD', 'World', 'Export in world space'),
-    ('ARMATURE', 'Armature', 'Export in armature space'),
-]
-
 class PSK_PG_material_list_item(PropertyGroup):
     material: PointerProperty(type=Material)
     index: IntProperty()
@@ -54,6 +49,11 @@ class PskExportMixin(ExportSpaceMixin, ForwardUpAxisMixin):
     bone_collection_list_index: IntProperty(default=0)
     material_name_list: CollectionProperty(type=PSK_PG_material_name_list_item)
     material_name_list_index: IntProperty(default=0)
+    root_bone_name: StringProperty(
+        name='Root Bone Name',
+        description='The name of the generated root bone when exporting multiple armatures',
+        default='ROOT',
+    )
 
 
 class PSK_PG_export(PropertyGroup, PskExportMixin):

io_scene_psk_psa/psk/writer.py

@@ -32,12 +32,13 @@ def write_psk(psk: Psk, path: str):
         raise RuntimeError(f'Number of materials ({len(psk.materials)}) exceeds limit of {MAX_MATERIAL_COUNT}')
     if len(psk.bones) > MAX_BONE_COUNT:
         raise RuntimeError(f'Number of bones ({len(psk.bones)}) exceeds limit of {MAX_BONE_COUNT}')
-    elif len(psk.bones) == 0:
+    if len(psk.bones) == 0:
         raise RuntimeError(f'At least one bone must be marked for export')
 
     # Make the directory for the file if it doesn't exist.
     os.makedirs(os.path.dirname(path), exist_ok=True)
 
+    try:
         with open(path, 'wb') as fp:
             _write_section(fp, b'ACTRHEAD')
             _write_section(fp, b'PNTS0000', Vector3, psk.points)
@@ -56,3 +57,5 @@ def write_psk(psk: Psk, path: str):
             _write_section(fp, b'MATT0000', Psk.Material, psk.materials)
             _write_section(fp, b'REFSKELT', Psk.Bone, psk.bones)
             _write_section(fp, b'RAWWEIGHTS', Psk.Weight, psk.weights)
+    except PermissionError as e:
+        raise RuntimeError(f'The current user "{os.getlogin()}" does not have permission to write to "{path}"') from e

io_scene_psk_psa/shared/data.py

@@ -161,13 +161,13 @@ class ForwardUpAxisMixin:
 
 export_space_items = [
     ('WORLD', 'World', 'Export in world space'),
-    ('ARMATURE', 'Armature', 'Export in armature 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',
-        description='Space to export the mesh in',
         items=export_space_items,
         default='WORLD'
     )

io_scene_psk_psa/shared/helpers.py

@@ -29,7 +29,7 @@ def get_nla_strips_in_frame_range(animation_data: AnimData, frame_min: float, fr
                 yield strip
 
 
-def populate_bone_collection_list(armature_object: Object, bone_collection_list: CollectionProperty) -> None:
+def populate_bone_collection_list(armature_objects: Iterable[Object], bone_collection_list: CollectionProperty) -> None:
     """
     Updates the bone collections collection.
 
@@ -39,7 +39,7 @@ def populate_bone_collection_list(armature_object: Object, bone_collection_list:
     has_selected_collections = any([g.is_selected for g in bone_collection_list])
     unassigned_collection_is_selected, selected_assigned_collection_names = True, []
 
-    if armature_object is None:
+    if not armature_objects:
         return
 
     if has_selected_collections:
@@ -54,13 +54,15 @@ def populate_bone_collection_list(armature_object: Object, bone_collection_list:
 
     bone_collection_list.clear()
 
+    for armature_object in armature_objects:
         armature = cast(Armature, armature_object.data)
 
         if armature is None:
             return
 
         item = bone_collection_list.add()
-    item.name = 'Unassigned'
+        item.armature_object_name = armature_object.name
+        item.name = 'Unassigned' # TODO: localize
         item.index = -1
         # Count the number of bones without an assigned bone collection
         item.count = sum(map(lambda bone: 1 if len(bone.collections) == 0 else 0, armature.bones))
@@ -68,6 +70,7 @@ def populate_bone_collection_list(armature_object: Object, bone_collection_list:
 
         for bone_collection_index, bone_collection in enumerate(armature.collections_all):
             item = bone_collection_list.add()
+            item.armature_object_name = armature_object.name
             item.name = bone_collection.name
             item.index = bone_collection_index
             item.count = len(bone_collection.bones)
@@ -131,6 +134,7 @@ def get_export_bone_names(armature_object: Object, bone_filter_mode: str, bone_c
     bone_names = [bones[x[0]].name for x in bone_indices]
 
     # Ensure that the hierarchy we are sending back has a single root bone.
+    # TODO: This is only relevant if we are exporting a single armature; how should we reorganize this call?
     bone_indices = [x[0] for x in bone_indices]
     root_bones = [bones[bone_index] for bone_index in bone_indices if bones[bone_index].parent is None]
     if len(root_bones) > 1:
@@ -159,20 +163,25 @@ 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
+
+
+# TODO: Perhaps export space should just be a transform matrix, since the below is not actually used unless we're using WORLD space.
 def convert_blender_bones_to_psx_bones(
-        bones: List[bpy.types.Bone],
+        bones: Iterable[bpy.types.Bone],
         bone_class: type,
-        export_space: str = 'WORLD',        # perhaps export space should just be a transform matrix, since the below is not actually used unless we're using WORLD space.
+        export_space: str = 'WORLD',
         armature_object_matrix_world: Matrix = Matrix.Identity(4),
         scale = 1.0,
         forward_axis: str = 'X',
-        up_axis: str = 'Z'
-) -> Iterable[type]:
-    '''
-    Function that converts a Blender bone list into a bone list that
-    @param bones:
-    @return:
-    '''
+        up_axis: str = 'Z',
+        root_bone: Optional = None,
+) -> Iterable:
+
     scale_matrix = Matrix.Scale(scale, 4)
 
     coordinate_system_transform = get_coordinate_system_transform(forward_axis, up_axis)
@@ -181,16 +190,7 @@ def convert_blender_bones_to_psx_bones(
     psx_bones = []
     for bone in bones:
         psx_bone = bone_class()
-
-        try:
-            psx_bone.name = bytes(bone.name, encoding='windows-1252')
-        except UnicodeEncodeError:
-            raise RuntimeError(
-                f'Bone name "{bone.name}" contains characters that cannot be encoded in the Windows-1252 codepage')
-
-        # TODO: flags & children_count should be initialized to zero anyways, so we can probably remove these lines?
-        psx_bone.flags = 0
-        psx_bone.children_count = 0
+        psx_bone.name = convert_string_to_cp1252_bytes(bone.name)
 
         try:
             parent_index = bones.index(bone.parent)
@@ -205,6 +205,22 @@ def convert_blender_bones_to_psx_bones(
             parent_head = inverse_parent_rotation @ bone.parent.head
             parent_tail = inverse_parent_rotation @ bone.parent.tail
             location = (parent_tail - parent_head) + bone.head
+        elif bone.parent is None and root_bone is not None:
+            # This is a special case for the root bone when export
+            # Because the root bone and child bones are in different spaces, we need to treat the root bone of this
+            # armature as though it were a child bone.
+            bone_rotation = bone.matrix.to_quaternion().conjugated()
+            local_rotation = armature_object_matrix_world.to_3x3().to_quaternion().conjugated()
+            rotation = bone_rotation @ local_rotation
+            translation, _, scale = armature_object_matrix_world.decompose()
+            # Invert the scale of the armature object matrix.
+            inverse_scale_matrix = Matrix.Identity(4)
+            inverse_scale_matrix[0][0] = 1.0 / scale.x
+            inverse_scale_matrix[1][1] = 1.0 / scale.y
+            inverse_scale_matrix[2][2] = 1.0 / scale.z
+
+            translation = translation @ inverse_scale_matrix
+            location = translation + bone.head
         else:
             def get_armature_local_matrix():
                 match export_space:
@@ -212,8 +228,10 @@ def convert_blender_bones_to_psx_bones(
                         return armature_object_matrix_world
                     case 'ARMATURE':
                         return Matrix.Identity(4)
+                    case 'ROOT':
+                        return bone.matrix.inverted()
                     case _:
-                        raise ValueError(f'Invalid export space: {export_space}')
+                        assert False, f'Invalid export space: {export_space}'
 
             armature_local_matrix = get_armature_local_matrix()
             location = armature_local_matrix @ bone.head
@@ -244,3 +262,23 @@ def convert_blender_bones_to_psx_bones(
         psx_bones.append(psx_bone)
 
     return psx_bones
+
+
+# TODO: we need two different ones for the PSK and PSA.
+# TODO: Figure out in what "space" the root bone is in for PSA animations.
+#  Maybe make a set of space-switching functions to make this easier to follow and figure out.
+def get_export_space_matrix(export_space: str, armature_object: Optional[Object] = None) -> Matrix:
+    match export_space:
+        case 'WORLD':
+            return Matrix.Identity(4)
+        case 'ARMATURE':
+            # We do not care about the scale when dealing with export spaces, only the translation and rotation.
+            if armature_object is not None:
+                translation, rotation, _ = armature_object.matrix_world.decompose()
+                return (rotation.to_matrix().to_4x4() @ Matrix.Translation(translation)).inverted()
+            else:
+                return Matrix.Identity(4)
+        case 'ROOT':
+            pass
+        case _:
+            assert False, f'Invalid export space: {export_space}'

io_scene_psk_psa/shared/types.py

@@ -1,3 +1,4 @@
+import bpy
 from bpy.props import StringProperty, IntProperty, BoolProperty, FloatProperty
 from bpy.types import PropertyGroup, UIList, UILayout, Context, AnyType, Panel
 
@@ -7,11 +8,19 @@ 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()
     name: StringProperty()
     index: IntProperty()
     count: IntProperty()