glTF exporter: Fix default sheen factors

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, 4, 11),
+    "version": (3, 4, 12),
     'blender': (3, 3, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_materials_sheen.py

@@ -29,6 +29,8 @@ def export_sheen(blender_material, export_settings):
     else:
         # Factor
         fac = gltf2_blender_get.get_factor_from_socket(sheenColor_socket, kind='RGB')
+        if fac is None:
+            fac = [1.0, 1.0, 1.0] # Default is 0.0/0.0/0.0, so we need to set it to 1 if no factor
         if fac is not None and fac != [0.0, 0.0, 0.0]:
             sheen_extension['sheenColorFactor'] = fac
         
@@ -51,6 +53,8 @@ def export_sheen(blender_material, export_settings):
     else:
         # Factor
         fac = gltf2_blender_get.get_factor_from_socket(sheenRoughness_socket, kind='VALUE')
+        if fac is None:
+            fac = 1.0 # Default is 0.0 so we need to set it to 1.0 if no factor
         if fac is not None and fac != 0.0:
             sheen_extension['sheenRoughnessFactor'] = fac