glTF exporter: store vertex colors as normalized ushorts

io_scene_gltf2/__init__.py

@@ -15,7 +15,7 @@
 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": (1, 4, 17),
+    "version": (1, 4, 18),
     'blender': (2, 90, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_gather_primitive_attributes.py

@@ -135,12 +135,32 @@ def __gather_colors(blender_primitive, export_settings):
         color_index = 0
         color_id = 'COLOR_' + str(color_index)
         while blender_primitive["attributes"].get(color_id) is not None:
-            internal_color = blender_primitive["attributes"][color_id]
-            attributes[color_id] = array_to_accessor(
-                internal_color,
-                component_type=gltf2_io_constants.ComponentType.Float,
-                data_type=gltf2_io_constants.DataType.Vec4,
+            colors = blender_primitive["attributes"][color_id]
+
+            if type(colors) is not np.ndarray:
+                colors = np.array(colors, dtype=np.float32)
+                colors = colors.reshape(len(colors) // 4, 4)
+
+            # Convert to normalized ushorts
+            colors *= 65535
+            colors += 0.5  # bias for rounding
+            colors = colors.astype(np.uint16)
+
+            attributes[color_id] = gltf2_io.Accessor(
+                buffer_view=gltf2_io_binary_data.BinaryData(colors.tobytes()),
+                byte_offset=None,
+                component_type=gltf2_io_constants.ComponentType.UnsignedShort,
+                count=len(colors),
+                extensions=None,
+                extras=None,
+                max=None,
+                min=None,
+                name=None,
+                normalized=True,
+                sparse=None,
+                type=gltf2_io_constants.DataType.Vec4,
             )
+
             color_index += 1
             color_id = 'COLOR_' + str(color_index)
     return attributes