scripts-blender/addons/asset_pipeline_2/constants.py

@@ -72,3 +72,6 @@ STAGED_PUBLISH_KEY = PUBLISH_KEYS[1]
 
 LOCAL_SUFFIX = "LOCAL"
 EXTERNAL_SUFFIX = "EXTERNAL"
+
+
+MATERIAL_ATTRIBUTE_NAME = "material_index"

scripts-blender/addons/asset_pipeline_2/transfer_data/transfer_functions.py

@@ -47,6 +47,7 @@ def transfer_vertex_group(
 
     source_obj.vertex_groups.active = source_obj.vertex_groups.get(vertex_group_name)
     # TODO Debug crashing / use context.temp_override(object=obj) style
+    # https://projects.blender.org/blender/blender/issues/112299
     context = bpy.context
     override = context.copy()
     override["selected_editable_objects"] = [target_obj, source_obj]
@@ -295,11 +296,7 @@ def material_slots_clean(obj):
     if transfer_data_list != []:
         return
 
-    for mat_slot in obj.material_slots:
-        index = obj.material_slots.keys().index(mat_slot.name)
-        obj.active_material_index = index
-        with context.temp_override(object=obj):
-            bpy.ops.object.material_slot_remove()
+    obj.data.materials.clear()
 
 
 def material_slots_is_missing(transfer_info):
@@ -330,25 +327,14 @@ def init_material_slots(scene, obj):
         )
 
 
-def transfer_material_slots(target_obj, source_obj):
-    # Delete existing material slot if exists
-    context = bpy.context
-    # Transfer material slot assignments.
+def transfer_material_slots(target_obj: bpy.types.Object, source_obj):
     # Delete all material slots of target object.
-    while len(target_obj.material_slots) > len(source_obj.material_slots):
-        target_obj.active_material_index = len(source_obj.material_slots)
-        with context.temp_override(object=target_obj):
-            bpy.ops.object.material_slot_remove()
+    target_obj.data.materials.clear()
 
     # Transfer material slots
     for idx in range(len(source_obj.material_slots)):
-        if idx >= len(target_obj.material_slots):
-            with context.temp_override(object=target_obj):
-                bpy.ops.object.material_slot_add()
+        target_obj.data.materials.append(source_obj.material_slots[idx].material)
         target_obj.material_slots[idx].link = source_obj.material_slots[idx].link
-        target_obj.material_slots[idx].material = source_obj.material_slots[
-            idx
-        ].material
 
     # Transfer active material slot index
     target_obj.active_material_index = source_obj.active_material_index
@@ -358,6 +344,9 @@ def transfer_material_slots(target_obj, source_obj):
         for spl_to, spl_from in zip(target_obj.data.splines, source_obj.data.splines):
             spl_to.material_index = spl_from.material_index
 
+    if source_obj.data.attributes.get(constants.MATERIAL_ATTRIBUTE_NAME):
+        transfer_attribute(constants.MATERIAL_ATTRIBUTE_NAME, target_obj, source_obj)
+
 
 # SHAPE KEYS
 
@@ -515,7 +504,11 @@ def transfer_shape_key(
 def attributes_get_editable(attributes):
     # TODO replace 'position' HACK with is_required once https://projects.blender.org/blender/blender/pulls/111468 is merged
     return [
-        item for item in attributes if not (item.is_internal or item.name == 'position')
+        item
+        for item in attributes
+        if not (
+            item.is_internal or item.name == 'position' or item.name == 'material_index'
+        )
     ]