glTF exporter: Fix transmission export

io_scene_gltf2/__init__.py

@@ -4,7 +4,7 @@
 bl_info = {
     'name': 'glTF 2.0 format',
     'author': 'Julien Duroure, Scurest, Norbert Nopper, Urs Hanselmann, Moritz Becher, Benjamin Schmithüsen, Jim Eckerlein, and many external contributors',
-    "version": (3, 2, 17),
+    "version": (3, 2, 18),
     'blender': (3, 1, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_materials.py

@@ -248,9 +248,10 @@ def __gather_extensions(blender_material, export_settings):
 
     # KHR_materials_transmission
 
-    transmission_extension = __gather_transmission_extension(blender_material, export_settings)
+    transmission_extension, use_actives_uvmap_transmission = __gather_transmission_extension(blender_material, export_settings)
     if transmission_extension:
         extensions["KHR_materials_transmission"] = transmission_extension
+        actives_uvmaps.extend(use_actives_uvmap_transmission)
 
     return extensions, actives_uvmaps if extensions else None
 
@@ -429,17 +430,19 @@ def __gather_transmission_extension(blender_material, export_settings):
         transmission_extension['transmissionFactor'] = transmission_socket.default_value
         transmission_enabled = transmission_extension['transmissionFactor'] > 0
     elif __has_image_node_from_socket(transmission_socket):
-        transmission_extension['transmissionFactor'] = 1
+        transmission_extension['transmissionFactor'] = 1.0
         has_transmission_texture = True
         transmission_enabled = True
 
     if not transmission_enabled:
-        return None
+        return None, None
 
     # Pack transmission channel (R).
     if has_transmission_texture:
         transmission_slots = (transmission_socket,)
 
+    use_actives_uvmaps = []
+
     if len(transmission_slots) > 0:
         combined_texture, use_active_uvmap = gltf2_blender_gather_texture_info.gather_texture_info(
             transmission_socket,
@@ -448,8 +451,10 @@ def __gather_transmission_extension(blender_material, export_settings):
         )
         if has_transmission_texture:
             transmission_extension['transmissionTexture'] = combined_texture
+        if use_active_uvmap:
+            use_actives_uvmaps.append("transmissionTexture")
 
-    return Extension('KHR_materials_transmission', transmission_extension, False), ["transmissionTexture"] if use_active_uvmap else []
+    return Extension('KHR_materials_transmission', transmission_extension, False), use_actives_uvmaps
 
 
 def __gather_material_unlit(blender_material, active_uvmap_index, export_settings):