Added material name mapping to collection exporter

Also moved a bunch of things around

.github/workflows/main.yml

@@ -30,7 +30,8 @@ jobs:
           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-mesa-glx -y
+          sudo apt-get install libgl1 -y
+          sudo apt-get install libglx-mesa0 -y
       - name: Download & Extract Blender
         run: |
           wget -q $BLENDER_URL

README.md

@@ -1,8 +1,18 @@
 [![Build Extension](https://github.com/DarklightGames/io_scene_ase/actions/workflows/main.yml/badge.svg)](https://github.com/DarklightGames/io_scene_ase/actions/workflows/main.yml)
 
-This is a Blender addon allowing you to export static meshes to the now-defunct ASE (ASCII Scene Export) format still in use in legacy programs like Unreal Tournament 2004.
+This is a Blender addon allowing you to export static meshes to the now-defunct ASE (ASCII Scene Export) format used in legacy programs like Unreal Tournament 2004.
 
-Check out [this video](https://www.youtube.com/watch?v=gpmBxCGHQjU) on how to install and use the addon.
+# Installation
+Install the latest version from [Blender Extensions](https://extensions.blender.org/add-ons/io-scene-ase/).
 
-Resources:
+Legacy versions are available on the [releases](https://github.com/DarklightGames/io_scene_ase/releases) page, but are not recommended for use.
+
+# Features
+* Selection and [collection exporters](https://docs.blender.org/manual/en/latest/scene_layout/collections/collections.html#exporters).
+* Full support for handling of [Collection Instances](https://docs.blender.org/manual/en/latest/scene_layout/object/properties/instancing/collection.html). 
+* Full support for multiple UV layers.
+* Easily reorder materials when using the collection exporter.
+* Support for scaling and coordinate system conversion on export.
+
+# Resources:
 * https://wiki.beyondunreal.com/Legacy:ASE_File_Format

io_scene_ase/__init__.py

@@ -3,16 +3,20 @@ if 'bpy' in locals():
     if 'ase'        in locals(): importlib.reload(ase)
     if 'builder'    in locals(): importlib.reload(builder)
     if 'writer'     in locals(): importlib.reload(writer)
+    if 'properties' in locals(): importlib.reload(properties)
     if 'exporter'   in locals(): importlib.reload(exporter)
+    if 'dfs'        in locals(): importlib.reload(dfs)
 
 import bpy
 import bpy.utils.previews
 from . import ase
 from . import builder
 from . import writer
+from . import properties
 from . import exporter
+from . import dfs
 
-classes = exporter.classes
+classes = properties.classes + exporter.classes
 
 
 def menu_func_export(self, context):
@@ -23,7 +27,8 @@ def register():
     for cls in classes:
         bpy.utils.register_class(cls)
 
-    bpy.types.Scene.ase_export = bpy.props.PointerProperty(type=exporter.ASE_PG_export)
+    bpy.types.Scene.ase_settings = bpy.props.PointerProperty(type=properties.ASE_PG_scene_settings, options={'HIDDEN'})
+    bpy.types.Scene.ase_export = bpy.props.PointerProperty(type=properties.ASE_PG_export, options={'HIDDEN'})
 
     bpy.types.TOPBAR_MT_file_export.append(menu_func_export)
 
@@ -31,6 +36,7 @@ def register():
 def unregister():
     bpy.types.TOPBAR_MT_file_export.remove(menu_func_export)
 
+    del bpy.types.Scene.ase_settings
     del bpy.types.Scene.ase_export
 
     for cls in classes:

io_scene_ase/ase.py

@@ -55,5 +55,5 @@ class ASEGeometryObject(object):
 
 class ASE(object):
     def __init__(self):
-        self.materials: List[Optional[Material]] = []
+        self.materials: List[str] = []
         self.geometry_objects = []

io_scene_ase/blender_manifest.toml

@@ -1,6 +1,6 @@
 schema_version = "1.0.0"
 id = "io_scene_ase"
-version = "2.1.3"
+version = "2.2.1"
 name = "ASCII Scene Export (.ase)"
 tagline = "Export .ase files used in Unreal Engine 1 & 2"
 maintainer = "Colin Basnett <cmbasnett@gmail.com>"

io_scene_ase/builder.py

@@ -1,6 +1,8 @@
-from typing import Iterable, Optional, List, Tuple
+from typing import Iterable, Optional, List, Dict, cast
+from collections import OrderedDict
 
-from bpy.types import Object, Context, Material, Mesh
+
+from bpy.types import Context, Material, Mesh
 
 from .ase import ASE, ASEGeometryObject, ASEFace, ASEFaceNormal, ASEVertexNormal, ASEUVLayer, is_collision_name
 import bpy
@@ -8,6 +10,8 @@ import bmesh
 import math
 from mathutils import Matrix, Vector
 
+from .dfs import DfsObject
+
 SMOOTHING_GROUP_MAX = 32
 
 class ASEBuildError(Exception):
@@ -18,45 +22,108 @@ class ASEBuildOptions(object):
     def __init__(self):
         self.object_eval_state = 'EVALUATED'
         self.materials: Optional[List[Material]] = None
+        self.material_mapping: Dict[str, str] = OrderedDict()
         self.transform = Matrix.Identity(4)
         self.should_export_vertex_colors = True
         self.vertex_color_mode = 'ACTIVE'
         self.has_vertex_colors = False
         self.vertex_color_attribute = ''
         self.should_invert_normals = False
+        self.scale = 1.0
+        self.forward_axis = 'X'
+        self.up_axis = 'Z'
 
 
-def get_object_matrix(obj: Object, asset_instance: Optional[Object] = None) -> Matrix:
-    if asset_instance is not None:
-        return asset_instance.matrix_world @ Matrix().Translation(asset_instance.instance_collection.instance_offset) @ obj.matrix_local
-    return obj.matrix_world
+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))
 
 
-def get_mesh_objects(objects: Iterable[Object]) -> List[Tuple[Object, Optional[Object]]]:
-    mesh_objects = []
-    for obj in objects:
-        if obj.type == 'MESH':
-            mesh_objects.append((obj, None))
-        elif obj.instance_collection:
-            for instance_object in obj.instance_collection.all_objects:
-                if instance_object.type == 'MESH':
-                    mesh_objects.append((instance_object, obj))
-    return mesh_objects
+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 build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Object]) -> ASE:
+def build_ase(context: Context, options: ASEBuildOptions, dfs_objects: Iterable[DfsObject]) -> ASE:
     ase = ASE()
+    ase.materials = [x.name if x is not None else 'None' for x in options.materials]
 
-    main_geometry_object = None
-    mesh_objects = get_mesh_objects(objects)
+    # If no materials are assigned to the object, add an empty material.
+    # This is necessary for the ASE format to be compatible with the UT2K4 importer.
+    if len(ase.materials) == 0:
+        ase.materials.append('')
 
-    context.window_manager.progress_begin(0, len(mesh_objects))
+    dfs_objects = list(dfs_objects)
+    dfs_objects_processed = 0
 
-    ase.materials = options.materials
+    context.window_manager.progress_begin(0, len(dfs_objects))
 
-    for object_index, (obj, asset_instance) in enumerate(mesh_objects):
+    class GeometryObjectInfo:
+        def __init__(self, name: str):
+            self.name = name
+            self.dfs_objects = []
 
-        matrix_world = get_object_matrix(obj, asset_instance)
+    main_geometry_object_info = GeometryObjectInfo('io_scene_ase')
+    geometry_object_infos: List[GeometryObjectInfo] = [
+        main_geometry_object_info,
+    ]
+
+    for object_index, dfs_object in enumerate(dfs_objects):
+        if is_collision_name(dfs_object.obj.name):
+            geometry_object_info = GeometryObjectInfo(dfs_object.obj.name)
+            geometry_object_info.dfs_objects.append(dfs_object)
+            geometry_object_infos.append(geometry_object_info)
+        else:
+            main_geometry_object_info.dfs_objects.append(dfs_object)
+
+    # Sort the DFS objects into collision and non-collision objects.
+    coordinate_system_transform = get_coordinate_system_transform(options.forward_axis, options.up_axis)
+
+    for geometry_object_info in geometry_object_infos:
+        geometry_object = ASEGeometryObject()
+        geometry_object.name = geometry_object_info.name
+
+        max_uv_layers = 0
+        for dfs_object in geometry_object_info.dfs_objects:
+            mesh_data = cast(Mesh, dfs_object.obj.data)
+            max_uv_layers = max(max_uv_layers, len(mesh_data.uv_layers))
+
+        geometry_object.uv_layers = [ASEUVLayer() for _ in range(max_uv_layers)]
+
+        for dfs_object in geometry_object_info.dfs_objects:
+            obj = dfs_object.obj
+
+            if geometry_object.is_collision:
+                # Test that collision meshes are manifold and convex.
+                bm = bmesh.new()
+                bm.from_mesh(obj.data)
+                for edge in bm.edges:
+                    if not edge.is_manifold:
+                        del bm
+                        raise ASEBuildError(f'Collision mesh \'{obj.name}\' is not manifold')
+                    if not edge.is_convex:
+                        del bm
+                        raise ASEBuildError(f'Collision mesh \'{obj.name}\' is not convex')
+
+            matrix_world = dfs_object.matrix_world
 
             # Save the active color name for vertex color export.
             active_color_name = obj.data.color_attributes.active_color_name
@@ -76,38 +143,22 @@ def build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Obje
                     mesh_object = bpy.data.objects.new('', mesh_data)
                     mesh_object.matrix_world = matrix_world
 
-        if not is_collision_name(obj.name) and main_geometry_object is not None:
-            geometry_object = main_geometry_object
-        else:
-            geometry_object = ASEGeometryObject()
-            geometry_object.name = obj.name
-            if not geometry_object.is_collision:
-                main_geometry_object = geometry_object
-            ase.geometry_objects.append(geometry_object)
+            vertex_transform = (Matrix.Rotation(math.pi, 4, 'Z') @
+                                Matrix.Scale(options.scale, 4) @
+                                options.transform @
+                                matrix_world)
 
-        if geometry_object.is_collision:
-            # Test that collision meshes are manifold and convex.
-            bm = bmesh.new()
-            bm.from_mesh(mesh_object.data)
-            for edge in bm.edges:
-                if not edge.is_manifold:
-                    del bm
-                    raise ASEBuildError(f'Collision mesh \'{obj.name}\' is not manifold')
-                if not edge.is_convex:
-                    del bm
-                    raise ASEBuildError(f'Collision mesh \'{obj.name}\' is not convex')
-
-        vertex_transform = Matrix.Rotation(math.pi, 4, 'Z') @ matrix_world
-
-        for vertex_index, vertex in enumerate(mesh_data.vertices):
-            geometry_object.vertices.append(vertex_transform @ vertex.co)
+            for _, vertex in enumerate(mesh_data.vertices):
+                vertex = vertex_transform @ vertex.co
+                vertex = coordinate_system_transform @ vertex
+                geometry_object.vertices.append(vertex)
 
             material_indices = []
             if not geometry_object.is_collision:
-            for mesh_material_index, material in enumerate(obj.data.materials):
+                for mesh_material_index, material in enumerate(obj.data.materials): # TODO: this needs to use the evaluated object, doesn't it?
                     if material is None:
                         raise ASEBuildError(f'Material slot {mesh_material_index + 1} for mesh \'{obj.name}\' cannot be empty')
-                material_indices.append(ase.materials.index(material))
+                    material_indices.append(ase.materials.index(material.name))
 
             if len(material_indices) == 0:
                 # If no materials are assigned to the mesh, just have a single empty material.
@@ -143,8 +194,17 @@ def build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Obje
 
             del face_material_indices
 
+            # TODO: There is an edge case here where if two different meshes have identical or nearly identical
+            # vertices and also matching smoothing groups, the engine's importer will incorrectly calculate the
+            # normal of any faces that have the shared vertices.
+            # The get around this, we could detect the overlapping vertices and display a warning, though checking
+            # for unique vertices can be quite expensive (use a KD-tree!)
+            # Another thing we can do is; when we find an overlapping vertex, we find out the range of smoothing
+            # groups that were used for that mesh. Then we can simply dodge the smoothing group by offseting the
+            # smoothing groups for the current mesh. This should work the majority of the time.
+
             # Faces
-        for face_index, loop_triangle in enumerate(mesh_data.loop_triangles):
+            for _, loop_triangle in enumerate(mesh_data.loop_triangles):
                 face = ASEFace()
                 face.a, face.b, face.c = map(lambda j: geometry_object.vertex_offset + mesh_data.loops[loop_triangle.loops[j]].vertex_index, loop_triangle_index_order)
                 if not geometry_object.is_collision:
@@ -161,7 +221,7 @@ def build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Obje
 
             if not geometry_object.is_collision:
                 # Normals
-            for face_index, loop_triangle in enumerate(mesh_data.loop_triangles):
+                for _, loop_triangle in enumerate(mesh_data.loop_triangles):
                     face_normal = ASEFaceNormal()
                     face_normal.normal = loop_triangle.normal
                     face_normal.vertex_normals = []
@@ -176,13 +236,17 @@ def build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Obje
 
                 # Texture Coordinates
                 for i, uv_layer_data in enumerate([x.data for x in mesh_data.uv_layers]):
-                if i >= len(geometry_object.uv_layers):
-                    geometry_object.uv_layers.append(ASEUVLayer())
                     uv_layer = geometry_object.uv_layers[i]
                     for loop_index, loop in enumerate(mesh_data.loops):
                         u, v = uv_layer_data[loop_index].uv
                         uv_layer.texture_vertices.append((u, v, 0.0))
 
+                # Add zeroed texture vertices for any missing UV layers.
+                for i in range(len(mesh_data.uv_layers), max_uv_layers):
+                    uv_layer = geometry_object.uv_layers[i]
+                    for _ in mesh_data.loops:
+                        uv_layer.texture_vertices.append((0.0, 0.0, 0.0))
+
                 # Texture Faces
                 for loop_triangle in mesh_data.loop_triangles:
                     geometry_object.texture_vertex_faces.append(
@@ -213,14 +277,24 @@ def build_ase(context: Context, options: ASEBuildOptions, objects: Iterable[Obje
             geometry_object.texture_vertex_offset += len(mesh_data.loops)
             geometry_object.vertex_offset = len(geometry_object.vertices)
 
-        context.window_manager.progress_update(object_index)
+            dfs_objects_processed += 1
+            context.window_manager.progress_update(dfs_objects_processed)
+
+        ase.geometry_objects.append(geometry_object)
+    
+    # Apply the material mapping.
+    material_mapping_items: list[tuple[str, str]] = list(options.material_mapping.items())
+    material_mapping_keys = list(map(lambda x: x[0], material_mapping_items))
+    for i in range(len(ase.materials)):
+        try:
+            index = material_mapping_keys.index(ase.materials[i])
+            ase.materials[i] = material_mapping_items[index][1]
+        except ValueError:
+            pass
 
     context.window_manager.progress_end()
 
     if len(ase.geometry_objects) == 0:
         raise ASEBuildError('At least one mesh object must be selected')
 
-    if main_geometry_object is None:
-        raise ASEBuildError('At least one non-collision mesh must be exported')
-
     return ase

io_scene_ase/dfs.py

@@ -0,0 +1,145 @@
+'''
+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 Optional, Set, Iterable, List
+
+from bpy.types import Collection, Object, ViewLayer, LayerCollection, Context
+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) -> 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: Optional[List[Object]] = None,
+        matrix_world: Matrix = Matrix.Identity(4),
+        visited: Optional[Set[Object]]=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.
+    '''
+    def layer_collection_objects_recursive(layer_collection: LayerCollection, visited: Set[Object]=None):
+        if visited is None:
+            visited = set()
+        for child in layer_collection.children:
+            yield from layer_collection_objects_recursive(child, visited=visited)
+        # 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_ase/exporter.py

@@ -1,69 +1,32 @@
-import os.path
 from typing import Iterable, List, Set, Union, cast, Optional
 
 import bpy
 from bpy_extras.io_utils import ExportHelper
-from bpy.props import StringProperty, CollectionProperty, PointerProperty, IntProperty, EnumProperty, BoolProperty
-from bpy.types import Operator, Material, PropertyGroup, UIList, Object, FileHandler, Event, Context, SpaceProperties, \
-    Collection
+from bpy.props import StringProperty, CollectionProperty, IntProperty, EnumProperty, BoolProperty
+from bpy.types import Operator, Material, UIList, Object, FileHandler, Event, Context, SpaceProperties, \
+    Collection, Panel, Depsgraph
 from mathutils import Matrix, Vector
 
-from .builder import ASEBuildOptions, ASEBuildError, get_mesh_objects, build_ase
+from .builder import ASEBuildOptions, ASEBuildError, build_ase
 from .writer import ASEWriter
+from .properties import TransformMixin, TransformSourceMixin, MaterialModeMixin, ASE_PG_key_value, get_vertex_color_attributes_from_objects
 
 
-class ASE_PG_material(PropertyGroup):
-    material: PointerProperty(type=Material)
-
-
-class ASE_PG_string(PropertyGroup):
-    string: StringProperty()
-
-
-def get_vertex_color_attributes_from_objects(objects: Iterable[Object]) -> Set[str]:
-    '''
-    Get the unique vertex color attributes from all the selected objects.
-    :param objects: The objects to search for vertex color attributes.
-    :return: A set of unique vertex color attributes.
-    '''
-    items = set()
-    for obj in filter(lambda x: x.type == 'MESH', objects):
-        for layer in filter(lambda x: x.domain == 'CORNER', obj.data.color_attributes):
-            items.add(layer.name)
-    return items
-
-
-def vertex_color_attribute_items(self, context):
-    # Get the unique color attributes from all the selected objects.
-    return [(x, x, '') for x in sorted(get_vertex_color_attributes_from_objects(context.selected_objects))]
-
-
-class ASE_PG_export(PropertyGroup):
-    material_list: CollectionProperty(name='Materials', type=ASE_PG_material)
-    material_list_index: IntProperty(name='Index', default=0)
-    should_export_vertex_colors: BoolProperty(name='Export Vertex Colors', default=True)
-    vertex_color_mode: EnumProperty(name='Vertex Color Mode', items=(
-        ('ACTIVE', 'Active', 'Use the active vertex color attribute'),
-        ('EXPLICIT', 'Explicit', 'Use the vertex color attribute specified below'),
-    ))
-    has_vertex_colors: BoolProperty(name='Has Vertex Colors', default=False, options={'HIDDEN'})
-    vertex_color_attribute: EnumProperty(name='Attribute', items=vertex_color_attribute_items)
-    should_invert_normals: BoolProperty(name='Invert Normals', default=False, description='Invert the normals of the exported geometry. This should be used if the software you are exporting to uses a different winding order than Blender')
-
-
-def get_unique_materials(mesh_objects: Iterable[Object]) -> List[Material]:
-    materials = set()
+def get_unique_materials(depsgraph: Depsgraph, mesh_objects: Iterable[Object]) -> List[Material]:
+    materials = []
     for mesh_object in mesh_objects:
-        for i, material_slot in enumerate(mesh_object.material_slots):
+        eo = mesh_object.evaluated_get(depsgraph)
+        for i, material_slot in enumerate(eo.material_slots):
             material = material_slot.material
-            if material is None:
-                raise RuntimeError(f'Material slots cannot be empty ({mesh_object.name}, material slot index {i})')
-            materials.add(material)
-    return list(materials)
+            # if material is None:
+                # raise RuntimeError(f'Material slots cannot be empty ({mesh_object.name}, material slot index {i})')
+            if material not in materials:
+                materials.append(material)
+    return materials
 
 
-def populate_material_list(mesh_objects: Iterable[Object], material_list):
-    materials = get_unique_materials(mesh_objects)
+def populate_material_list(depsgraph: Depsgraph, mesh_objects: Iterable[Object], material_list):
+    materials = get_unique_materials(depsgraph, mesh_objects)
     material_list.clear()
     for index, material in enumerate(materials):
         m = material_list.add()
@@ -94,10 +57,10 @@ def get_collection_export_operator_from_context(context: Context) -> Optional['A
     return exporter.export_properties
 
 
-class ASE_OT_material_order_add(Operator):
-    bl_idname = 'ase_export.material_order_add'
+class ASE_OT_material_mapping_add(Operator):
+    bl_idname = 'ase_export.material_mapping_add'
     bl_label = 'Add'
-    bl_description = 'Add a material to the list'
+    bl_description = 'Add a material mapping to the list'
 
     def invoke(self, context: Context, event: Event) -> Union[Set[str], Set[int]]:
         # TODO: get the region that this was invoked from and set the collection to the collection of the region.
@@ -111,23 +74,23 @@ class ASE_OT_material_order_add(Operator):
         if operator is None:
             return {'INVALID_CONTEXT'}
 
-        material_string = operator.material_order.add()
-        material_string.string = 'Material'
+        material_mapping = operator.material_mapping.add()
+        material_mapping.key = 'Material'
 
         return {'FINISHED'}
 
 
-class ASE_OT_material_order_remove(Operator):
-    bl_idname = 'ase_export.material_order_remove'
+class ASE_OT_material_mapping_remove(Operator):
+    bl_idname = 'ase_export.material_mapping_remove'
     bl_label = 'Remove'
-    bl_description = 'Remove the selected material from the list'
+    bl_description = 'Remove the selected material mapping from the list'
 
     @classmethod
     def poll(cls, context: Context):
         operator = get_collection_export_operator_from_context(context)
         if operator is None:
             return False
-        return 0 <= operator.material_order_index < len(operator.material_order)
+        return 0 <= operator.material_mapping_index < len(operator.material_mapping)
 
     def execute(self, context: 'Context') -> Union[Set[str], Set[int]]:
         operator = get_collection_export_operator_from_context(context)
@@ -135,22 +98,22 @@ class ASE_OT_material_order_remove(Operator):
         if operator is None:
             return {'INVALID_CONTEXT'}
 
-        operator.material_order.remove(operator.material_order_index)
+        operator.material_mapping.remove(operator.material_mapping_index)
 
         return {'FINISHED'}
 
 
-class ASE_OT_material_order_move_up(Operator):
-    bl_idname = 'ase_export.material_order_move_up'
+class ASE_OT_material_mapping_move_up(Operator):
+    bl_idname = 'ase_export.material_mapping_move_up'
     bl_label = 'Move Up'
-    bl_description = 'Move the selected material up one slot'
+    bl_description = 'Move the selected material mapping up one slot'
 
     @classmethod
     def poll(cls, context: Context):
         operator = get_collection_export_operator_from_context(context)
         if operator is None:
             return False
-        return operator.material_order_index > 0
+        return operator.material_mapping_index > 0
 
     def execute(self, context: 'Context') -> Union[Set[str], Set[int]]:
         operator = get_collection_export_operator_from_context(context)
@@ -158,23 +121,23 @@ class ASE_OT_material_order_move_up(Operator):
         if operator is None:
             return {'INVALID_CONTEXT'}
 
-        operator.material_order.move(operator.material_order_index, operator.material_order_index - 1)
-        operator.material_order_index -= 1
+        operator.material_mapping.move(operator.material_mapping_index, operator.material_mapping_index - 1)
+        operator.material_mapping_index -= 1
 
         return {'FINISHED'}
 
 
-class ASE_OT_material_order_move_down(Operator):
-    bl_idname = 'ase_export.material_order_move_down'
+class ASE_OT_material_mapping_move_down(Operator):
+    bl_idname = 'ase_export.material_mapping_move_down'
     bl_label = 'Move Down'
-    bl_description = 'Move the selected material down one slot'
+    bl_description = 'Move the selected material mapping down one slot'
 
     @classmethod
     def poll(cls, context: Context):
         operator = get_collection_export_operator_from_context(context)
         if operator is None:
             return False
-        return operator.material_order_index < len(operator.material_order) - 1
+        return operator.material_mapping_index < len(operator.material_mapping) - 1
 
     def execute(self, context: 'Context') -> Union[Set[str], Set[int]]:
         operator = get_collection_export_operator_from_context(context)
@@ -182,8 +145,8 @@ class ASE_OT_material_order_move_down(Operator):
         if operator is None:
             return {'INVALID_CONTEXT'}
 
-        operator.material_order.move(operator.material_order_index, operator.material_order_index + 1)
-        operator.material_order_index += 1
+        operator.material_mapping.move(operator.material_mapping_index, operator.material_mapping_index + 1)
+        operator.material_mapping_index += 1
 
         return {'FINISHED'}
 
@@ -225,25 +188,61 @@ class ASE_OT_material_list_move_down(Operator):
 
 
 class ASE_UL_materials(UIList):
+    bl_idname = 'ASE_UL_materials'
+
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index):
         row = layout.row()
         row.prop(item.material, 'name', text='', emboss=False, icon_value=layout.icon(item.material))
 
 
-class ASE_UL_strings(UIList):
+class ASE_UL_material_names(UIList):
+    bl_idname = 'ASE_UL_material_names'
+
     def draw_item(self, context, layout, data, item, icon, active_data, active_propname, index):
         row = layout.row()
-        row.prop(item, 'string', text='', emboss=False)
+        material = bpy.data.materials.get(item.key, None)
+        col= row.column()
+        col.enabled = False
+        col.prop(item, 'key', text='', emboss=False, icon_value=layout.icon(material) if material is not None else 0)
+        row.label(icon='RIGHTARROW', text='')
+        material = bpy.data.materials.get(item.value, None)
+        row.prop(item, 'value', text='', emboss=False, icon_value=layout.icon(material) if material is not None else 0)
 
 
+class ASE_OT_material_names_populate(Operator):
+    bl_idname = 'ase_export.material_names_populate'
+    bl_label = 'Populate Material Names List'
+    bl_description = 'Populate the material names with the materials used by objects in the collection'
 
-object_eval_state_items = (
+    def execute(self, context):
+        collection = get_collection_from_context(context)
+        operator = get_collection_export_operator_from_context(context)
+        if operator is None:
+            return {'CANCELLED'}
+
+        from .dfs import dfs_collection_objects
+
+        mesh_objects = list(map(lambda x: x.obj, filter(lambda x: x.obj.type == 'MESH', dfs_collection_objects(collection))))
+
+        # Exclude objects that are not visible.
+        materials = get_unique_materials(context.evaluated_depsgraph_get(), mesh_objects)
+
+        operator.material_mapping.clear()
+        for material in materials:
+            m = operator.material_mapping.add()
+            m.key = material.name
+            m.value = material.name
+
+        return {'FINISHED'}
+
+
+object_eval_state_items = [
     ('EVALUATED', 'Evaluated', 'Use data from fully evaluated object'),
     ('ORIGINAL', 'Original', 'Use data from original object with no modifiers applied'),
-)
+]
 
 
-class ASE_OT_export(Operator, ExportHelper):
+class ASE_OT_export(Operator, ExportHelper, TransformMixin, TransformSourceMixin):
     bl_idname = 'io_scene_ase.ase_export'
     bl_label = 'Export ASE'
     bl_space_type = 'PROPERTIES'
@@ -259,8 +258,8 @@ class ASE_OT_export(Operator, ExportHelper):
 
     @classmethod
     def poll(cls, context):
-        if not any(x.type == 'MESH' for x in context.selected_objects):
-            cls.poll_message_set('At least one mesh must be selected')
+        if not any(x.type == 'MESH' or (x.type == 'EMPTY' and x.instance_collection is not None) for x in context.selected_objects):
+            cls.poll_message_set('At least one mesh or instanced collection must be selected')
             return False
         return True
 
@@ -268,6 +267,10 @@ class ASE_OT_export(Operator, ExportHelper):
         layout = self.layout
         pg = context.scene.ase_export
 
+        flow = layout.grid_flow()
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+
         materials_header, materials_panel = layout.panel('Materials', default_closed=False)
         materials_header.label(text='Materials')
 
@@ -278,7 +281,6 @@ class ASE_OT_export(Operator, ExportHelper):
             col.operator(ASE_OT_material_list_move_up.bl_idname, icon='TRIA_UP', text='')
             col.operator(ASE_OT_material_list_move_down.bl_idname, icon='TRIA_DOWN', text='')
 
-
         has_vertex_colors = len(get_vertex_color_attributes_from_objects(context.selected_objects)) > 0
         vertex_colors_header, vertex_colors_panel = layout.panel_prop(pg, 'should_export_vertex_colors')
         row = vertex_colors_header.row()
@@ -295,6 +297,16 @@ class ASE_OT_export(Operator, ExportHelper):
             else:
                 vertex_colors_panel.label(text='No vertex color attributes found')
 
+        transform_header, transform_panel = layout.panel('Transform', default_closed=True)
+        transform_header.label(text='Transform')
+
+        if transform_panel:
+            transform_panel.use_property_split = True
+            transform_panel.use_property_decorate = False
+            transform_panel.prop(self, 'scale')
+            transform_panel.prop(self, 'forward_axis')
+            transform_panel.prop(self, 'up_axis')
+
         advanced_header, advanced_panel = layout.panel('Advanced', default_closed=True)
         advanced_header.label(text='Advanced')
 
@@ -305,12 +317,18 @@ class ASE_OT_export(Operator, ExportHelper):
             advanced_panel.prop(pg, 'should_invert_normals')
 
     def invoke(self, context: 'Context', event: 'Event' ) -> Union[Set[str], Set[int]]:
-        mesh_objects = [x[0] for x in get_mesh_objects(context.selected_objects)]
+        from .dfs import dfs_view_layer_objects
+
+        mesh_objects = list(map(lambda x: x.obj, filter(lambda x: x.is_selected and x.obj.type == 'MESH', dfs_view_layer_objects(context.view_layer))))
+
+        if len(mesh_objects) == 0:
+            self.report({'ERROR'}, 'No mesh objects selected')
+            return {'CANCELLED'}
 
         pg = getattr(context.scene, 'ase_export')
 
         try:
-            populate_material_list(mesh_objects, pg.material_list)
+            populate_material_list(context.evaluated_depsgraph_get(), mesh_objects, pg.material_list)
         except RuntimeError as e:
             self.report({'ERROR'}, str(e))
             return {'CANCELLED'}
@@ -332,14 +350,29 @@ class ASE_OT_export(Operator, ExportHelper):
         options.vertex_color_attribute = pg.vertex_color_attribute
         options.materials = [x.material for x in pg.material_list]
         options.should_invert_normals = pg.should_invert_normals
+
+        match self.transform_source:
+            case 'SCENE':
+                transform_source = getattr(context.scene, 'ase_settings')
+            case 'OBJECT':
+                transform_source = self
+
+        options.scale = transform_source.scale
+        options.forward_axis = transform_source.forward_axis
+        options.up_axis = transform_source.up_axis
+
+        from .dfs import dfs_view_layer_objects
+
+        dfs_objects = list(filter(lambda x: x.is_selected and x.obj.type == 'MESH', dfs_view_layer_objects(context.view_layer)))
+
         try:
-            ase = build_ase(context, options, context.selected_objects)
+            ase = build_ase(context, options, dfs_objects)
 
             # Calculate some statistics about the ASE file to display in the console.
             object_count = len(ase.geometry_objects)
             material_count = len(ase.materials)
-            vertex_count = sum(len(x.vertices) for x in ase.geometry_objects)
             face_count = sum(len(x.faces) for x in ase.geometry_objects)
+            vertex_count = sum(len(x.vertices) for x in ase.geometry_objects)
 
             ASEWriter().write(self.filepath, ase)
             self.report({'INFO'}, f'ASE exported successfully ({object_count} objects, {material_count} materials, {face_count} faces, {vertex_count} vertices)')
@@ -349,7 +382,14 @@ class ASE_OT_export(Operator, ExportHelper):
             return {'CANCELLED'}
 
 
-class ASE_OT_export_collection(Operator, ExportHelper):
+export_space_items = [
+    ('WORLD', 'World Space', 'Export the collection in world space'),
+    ('INSTANCE', 'Instance Space', 'Export the collection in instance space'),
+    ('OBJECT', 'Object Space', 'Export the collection in the active object\'s local space'),
+]
+
+
+class ASE_OT_export_collection(Operator, ExportHelper, TransformSourceMixin, TransformMixin, MaterialModeMixin):
     bl_idname = 'io_scene_ase.ase_export_collection'
     bl_label = 'Export collection to ASE'
     bl_space_type = 'PROPERTIES'
@@ -368,25 +408,55 @@ class ASE_OT_export_collection(Operator, ExportHelper):
     )
 
     collection: StringProperty()
-    material_order: CollectionProperty(name='Materials', type=ASE_PG_string)
-    material_order_index: IntProperty(name='Index', default=0)
-
+    material_mapping: CollectionProperty(name='Materials', type=ASE_PG_key_value)
+    material_mapping_index: IntProperty(name='Index', default=0)
+    export_space: EnumProperty(name='Export Space', items=export_space_items, default='INSTANCE')
 
     def draw(self, context):
         layout = self.layout
 
-        materials_header, materials_panel = layout.panel('Materials', default_closed=False)
+        flow = layout.grid_flow()
+        flow.use_property_split = True
+        flow.use_property_decorate = False
+
+        materials_header, materials_panel = layout.panel('Materials', default_closed=True)
         materials_header.label(text='Materials')
 
         if materials_panel:
+            materials_panel.prop(self, 'material_mode', text='Material Mode')
+            if self.material_mode == 'MANUAL':
                 row = materials_panel.row()
-            row.template_list('ASE_UL_strings', '', self, 'material_order', self, 'material_order_index')
+                row.template_list(ASE_UL_material_names.bl_idname, '', self, 'material_mapping', self, 'material_mapping_index')
                 col = row.column(align=True)
-            col.operator(ASE_OT_material_order_add.bl_idname, icon='ADD', text='')
-            col.operator(ASE_OT_material_order_remove.bl_idname, icon='REMOVE', text='')
+                col.operator(ASE_OT_material_mapping_add.bl_idname, icon='ADD', text='')
+                col.operator(ASE_OT_material_mapping_remove.bl_idname, icon='REMOVE', text='')
                 col.separator()
-            col.operator(ASE_OT_material_order_move_up.bl_idname, icon='TRIA_UP', text='')
-            col.operator(ASE_OT_material_order_move_down.bl_idname, icon='TRIA_DOWN', text='')
+                col.operator(ASE_OT_material_mapping_move_up.bl_idname, icon='TRIA_UP', text='')
+                col.operator(ASE_OT_material_mapping_move_down.bl_idname, icon='TRIA_DOWN', text='')
+                col.separator()
+                col.operator(ASE_OT_material_names_populate.bl_idname, icon='FILE_REFRESH', text='')
+
+        transform_header, transform_panel = layout.panel('Transform', default_closed=True)
+        transform_header.label(text='Transform')
+
+        if transform_panel:
+            transform_panel.use_property_split = True
+            transform_panel.use_property_decorate = False
+            transform_panel.prop(self, 'transform_source')
+
+            flow = transform_panel.grid_flow()
+            match self.transform_source:
+                case 'SCENE':
+                    transform_source = getattr(context.scene, 'ase_settings')
+                    flow.enabled = False
+                case 'OBJECT':
+                    transform_source = self
+
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(transform_source, 'scale')
+            flow.prop(transform_source, 'forward_axis')
+            flow.prop(transform_source, 'up_axis')
 
         advanced_header, advanced_panel = layout.panel('Advanced', default_closed=True)
         advanced_header.label(text='Advanced')
@@ -395,28 +465,65 @@ class ASE_OT_export_collection(Operator, ExportHelper):
             advanced_panel.use_property_split = True
             advanced_panel.use_property_decorate = False
             advanced_panel.prop(self, 'object_eval_state')
+            advanced_panel.prop(self, 'export_space')
 
     def execute(self, context):
         collection = bpy.data.collections.get(self.collection)
 
         options = ASEBuildOptions()
         options.object_eval_state = self.object_eval_state
-        options.transform = Matrix.Translation(-Vector(collection.instance_offset))
 
-        # Iterate over all the objects in the collection.
-        mesh_objects = get_mesh_objects(collection.all_objects)
+        match self.transform_source:
+            case 'SCENE':
+                transform_source = getattr(context.scene, 'ase_settings')
+            case 'OBJECT':
+                transform_source = self
+
+        options.scale = transform_source.scale
+        options.forward_axis = transform_source.forward_axis
+        options.up_axis = transform_source.up_axis
+
+        match self.export_space:
+            case 'WORLD':
+                options.transform = Matrix.Identity(4)
+            case 'INSTANCE':
+                options.transform = Matrix.Translation(-Vector(collection.instance_offset))
+            case 'BONE':
+                options.transform = Matrix
+
+        from .dfs import dfs_collection_objects
+
+        dfs_objects = list(filter(lambda x: x.obj.type == 'MESH', dfs_collection_objects(collection)))
+        mesh_objects = [x.obj for x in dfs_objects]
 
         # Get all the materials used by the objects in the collection.
-        options.materials = get_unique_materials([x[0] for x in mesh_objects])
+        options.materials = get_unique_materials(context.evaluated_depsgraph_get(), mesh_objects)
+
+        if self.material_mode == 'MANUAL':
+            # Build material mapping.
+            for material_mapping in self.material_mapping:
+                options.material_mapping[material_mapping.key] = material_mapping.value
 
             # Sort the materials based on the order in the material order list, keeping in mind that the material order list
             # may not contain all the materials used by the objects in the collection.
-        material_order = [x.string for x in self.material_order]
-        material_order_map = {x: i for i, x in enumerate(material_order)}
-        options.materials.sort(key=lambda x: material_order_map.get(x.name, len(material_order)))
+            material_names = [x.key for x in self.material_mapping]
+            material_names_map = {x: i for i, x in enumerate(material_names)}
+
+            # Split the list of materials into two lists: one for materials that appear in the material order list, and one
+            # for materials that do not. Then append the two lists together, with the ordered materials first.
+            ordered_materials = []
+            unordered_materials = []
+            for material in options.materials:
+                if material.name in material_names_map:
+                    ordered_materials.append(material)
+                else:
+                    unordered_materials.append(material)
+
+            ordered_materials.sort(key=lambda x: material_names_map.get(x.name, len(material_names)))
+            options.materials = ordered_materials + unordered_materials
 
         try:
-            ase = build_ase(context, options, collection.all_objects)
+            ase = build_ase(context, options, dfs_objects)
         except ASEBuildError as e:
             self.report({'ERROR'}, str(e))
             return {'CANCELLED'}
@@ -430,6 +537,35 @@ class ASE_OT_export_collection(Operator, ExportHelper):
         return {'FINISHED'}
 
 
+class ASE_PT_export_scene_settings(Panel):
+    bl_label = 'ASCII Scene Export'
+    bl_space_type = 'PROPERTIES'
+    bl_region_type = 'WINDOW'
+    bl_context = 'scene'
+    bl_options = {'DEFAULT_CLOSED'}
+
+    @classmethod
+    def poll(cls, context: Context):
+        return context.space_data.type == 'PROPERTIES' and hasattr(context.scene, 'ase_settings')
+    
+    def draw(self, context: Context):
+        layout = self.layout
+
+        transform_source = getattr(context.scene, 'ase_settings')
+
+        transform_header, transform_panel = layout.panel('Transform', default_closed=True)
+        transform_header.label(text='Transform')
+
+        if transform_panel:
+            flow = transform_panel.grid_flow()
+            flow.use_property_split = True
+            flow.use_property_decorate = False
+            flow.prop(transform_source, 'scale')
+            flow.prop(transform_source, 'forward_axis')
+            flow.prop(transform_source, 'up_axis')
+
+
+
 class ASE_FH_export(FileHandler):
     bl_idname = 'ASE_FH_export'
     bl_label = 'ASCII Scene Export'
@@ -437,20 +573,18 @@ class ASE_FH_export(FileHandler):
     bl_file_extensions = '.ase'
 
 
-
 classes = (
-    ASE_PG_material,
-    ASE_PG_string,
     ASE_UL_materials,
-    ASE_UL_strings,
-    ASE_PG_export,
+    ASE_UL_material_names,
     ASE_OT_export,
     ASE_OT_export_collection,
     ASE_OT_material_list_move_down,
     ASE_OT_material_list_move_up,
-    ASE_OT_material_order_add,
-    ASE_OT_material_order_remove,
-    ASE_OT_material_order_move_down,
-    ASE_OT_material_order_move_up,
+    ASE_OT_material_mapping_add,
+    ASE_OT_material_mapping_remove,
+    ASE_OT_material_mapping_move_down,
+    ASE_OT_material_mapping_move_up,
+    ASE_OT_material_names_populate,
+    ASE_PT_export_scene_settings,
     ASE_FH_export,
 )

io_scene_ase/properties.py

@@ -0,0 +1,114 @@
+from typing import Iterable, Set
+from bpy.types import PropertyGroup, Context, Material, Object
+from bpy.props import CollectionProperty, IntProperty, BoolProperty, EnumProperty, FloatProperty, StringProperty, PointerProperty
+
+
+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: Context):
+    if self.forward_axis[-1] == self.up_axis[-1]:
+        self.up_axis = next((axis for axis in axis_identifiers if axis[-1] != self.forward_axis[-1]), 'Z')
+
+
+def up_axis_update(self, _context: Context):
+    if self.up_axis[-1] == self.forward_axis[-1]:
+        self.forward_axis = next((axis for axis in axis_identifiers if axis[-1] != self.up_axis[-1]), 'X')
+
+
+transform_source_items = (
+    ('SCENE', 'Scene', ''),
+    ('CUSTOM', 'Custom', ''),
+)
+
+
+class TransformSourceMixin:
+    transform_source: EnumProperty(name='Transform Source', items=transform_source_items, default='SCENE', description='The source of the transform to apply to the exported geometry')
+
+
+class TransformMixin:
+    scale: FloatProperty(name='Scale', default=1.0, min=0.0001, soft_max=1000.0, description='Scale factor to apply to the exported geometry')
+    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)
+
+
+material_mode_items = (
+    ('AUTOMATIC', 'Automatic', ''),
+    ('MANUAL', 'Manual', ''),
+)
+
+
+class MaterialModeMixin:
+    material_mode: EnumProperty(name='Material Mode', items=material_mode_items, default='AUTOMATIC', description='The material mode to use for the exported geometry')
+
+
+class ASE_PG_material(PropertyGroup):
+    material: PointerProperty(type=Material)
+
+
+class ASE_PG_key_value(PropertyGroup):
+    key: StringProperty()
+    value: StringProperty()
+
+
+def get_vertex_color_attributes_from_objects(objects: Iterable[Object]) -> Set[str]:
+    '''
+    Get the unique vertex color attributes from all the selected objects.
+    :param objects: The objects to search for vertex color attributes.
+    :return: A set of unique vertex color attributes.
+    '''
+    items = set()
+    for obj in filter(lambda x: x.type == 'MESH', objects):
+        for layer in filter(lambda x: x.domain == 'CORNER', obj.data.color_attributes):
+            items.add(layer.name)
+    return items
+
+
+def vertex_color_attribute_items(self, context):
+    # Get the unique color attributes from all the selected objects.
+    return [(x, x, '') for x in sorted(get_vertex_color_attributes_from_objects(context.selected_objects))]
+
+
+vertex_color_mode_items = (
+    ('ACTIVE', 'Active', 'Use the active vertex color attribute'),
+    ('EXPLICIT', 'Explicit', 'Use the vertex color attribute specified below'),
+)
+
+
+class ASE_PG_export(PropertyGroup, TransformSourceMixin, TransformMixin):
+    material_list: CollectionProperty(name='Materials', type=ASE_PG_material)
+    material_list_index: IntProperty(name='Index', default=0)
+    should_export_vertex_colors: BoolProperty(name='Export Vertex Colors', default=True)
+    vertex_color_mode: EnumProperty(name='Vertex Color Mode', items=vertex_color_mode_items)
+    has_vertex_colors: BoolProperty(name='Has Vertex Colors', default=False, options={'HIDDEN'})
+    vertex_color_attribute: EnumProperty(name='Attribute', items=vertex_color_attribute_items)
+    should_invert_normals: BoolProperty(name='Invert Normals', default=False, description='Invert the normals of the exported geometry. This should be used if the software you are exporting to uses a different winding order than Blender')
+
+
+class ASE_PG_scene_settings(PropertyGroup, TransformMixin):
+    pass
+
+
+classes = (
+    ASE_PG_material,
+    ASE_PG_key_value,
+    ASE_PG_export,
+    ASE_PG_scene_settings,
+)

io_scene_ase/writer.py

@@ -118,6 +118,12 @@ class ASEWriter(object):
                 submaterial_node.push_child('MATERIAL_NAME').push_datum(material)
                 diffuse_node = submaterial_node.push_child('MAP_DIFFUSE')
                 diffuse_node.push_child('MAP_NAME').push_datum('default')
+                # For inscrutible reasons, the UT2K4 ASE importer uses the BITMAP value
+                # when doing material lookups on import. It also has a hard-coded bit of logic to
+                # strip off the extension, so we must oblige and tack on the .bmp extension.
+                # In addition, it must have a leading backslash in order to find the beginning
+                # of the path.
+                diffuse_node.push_child('BITMAP').push_datum(f'\\{material}.bmp')
                 diffuse_node.push_child('UVW_U_OFFSET').push_datum(0.0)
                 diffuse_node.push_child('UVW_V_OFFSET').push_datum(0.0)
                 diffuse_node.push_child('UVW_U_TILING').push_datum(1.0)
@@ -182,8 +188,8 @@ class ASEWriter(object):
                 cvert_list = mesh_node.push_child('MESH_CVERTLIST')
                 for i, vertex_color in enumerate(geometry_object.vertex_colors):
                     cvert_list.push_child('MESH_VERTCOL').push_datum(i).push_data(vertex_color)
-                parent_node.push_child('MESH_NUMCVFACES').push_datum(len(geometry_object.texture_vertex_faces))
-                texture_faces_node = parent_node.push_child('MESH_CFACELIST')
+                mesh_node.push_child('MESH_NUMCVFACES').push_datum(len(geometry_object.texture_vertex_faces))
+                texture_faces_node = mesh_node.push_child('MESH_CFACELIST')
                 for texture_face_index, texture_face in enumerate(geometry_object.texture_vertex_faces):
                     texture_face_node = texture_faces_node.push_child('MESH_CFACE')
                     texture_face_node.push_data([texture_face_index] + list(texture_face))