Fixed a bug where exporting more than two mesh objects would result in a corrupted ASE file.

README.md

@@ -1,3 +1,5 @@
 # io_scene_ase
 
 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.
+
+Check out [this video](https://www.youtube.com/watch?v=gpmBxCGHQjU) on how to install and use the addon.

src/__init__.py

@@ -2,7 +2,7 @@ bl_info = {
     'name': 'ASCII Scene Export',
     'description': 'Export ASE (ASCII Scene Export) files',
     'author': 'Colin Basnett (Darklight Games)',
-    'version': (1, 0, 0),
+    'version': (1, 0, 3),
     'blender': (2, 90, 0),
     'location': 'File > Import-Export',
     'warning': 'This add-on is under development.',

src/builder.py

@@ -37,7 +37,6 @@ class ASEBuilder(object):
             if not geometry_object.is_collision and len(mesh_data.materials) == 0:
                 raise ASEBuilderError(f'Mesh \'{obj.name}\' must have at least one material')
 
-            geometry_object.vertex_offset += len(geometry_object.vertices)
             vertex_transform = Matrix.Scale(options.scale, 4) @ Matrix.Rotation(math.pi, 4, 'Z') @ obj.matrix_world
             for vertex_index, vertex in enumerate(mesh_data.vertices):
                 geometry_object.vertices.append(vertex_transform @ vertex.co)
@@ -67,7 +66,14 @@ class ASEBuilder(object):
                 face.c = geometry_object.vertex_offset + mesh_data.loops[loop_triangle.loops[2]].vertex_index
                 if not geometry_object.is_collision:
                     face.material_index = material_indices[loop_triangle.material_index]
-                face.smoothing = poly_groups[loop_triangle.polygon_index]
+                # The UT2K4 importer only accepts 32 smoothing groups. Anything past this completely mangles the
+                # smoothing groups and effectively makes the whole model use sharp-edge rendering.
+                # The fix is to constrain the smoothing group between 0 and 31 by applying a modulo of 32 to the actual
+                # smoothing group index.
+                # This may result in bad calculated normals on export in rare cases. For example, if a face with a
+                # smoothing group of 3 is adjacent to a face with a smoothing group of 35 (35 % 32 == 3), those faces
+                # will be treated as part of the same smoothing group.
+                face.smoothing = (poly_groups[loop_triangle.polygon_index] - 1) % 32
                 geometry_object.faces.append(face)
 
             # Normals
@@ -86,7 +92,6 @@ class ASEBuilder(object):
             uv_layer = mesh_data.uv_layers.active.data
 
             # Texture Coordinates
-            geometry_object.texture_vertex_offset += len(geometry_object.texture_vertices)
             if not geometry_object.is_collision:
                 for loop_index, loop in enumerate(mesh_data.loops):
                     u, v = uv_layer[loop_index].uv
@@ -101,6 +106,10 @@ class ASEBuilder(object):
                         geometry_object.texture_vertex_offset + loop_triangle.loops[2]
                     ))
 
+            # Update data offsets for next iteration
+            geometry_object.texture_vertex_offset = len(geometry_object.texture_vertices)
+            geometry_object.vertex_offset = len(geometry_object.vertices)
+
         if len(ase.geometry_objects) == 0:
             raise ASEBuilderError('At least one mesh object must be selected')
 

src/exporter.py

@@ -19,7 +19,7 @@ class ASE_OT_ExportOperator(bpy.types.Operator, bpy_extras.io_utils.ExportHelper
         maxlen=255,  # Max internal buffer length, longer would be hilighted.
     )
 
-    units = EnumProperty(
+    units: EnumProperty(
         items=(('M', 'Meters', ''),
                ('U', 'Unreal', '')),
         name='Units'