glTF: use color attribute API instead of vertex color

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, 37),
+    "version": (3, 2, 38),
     'blender': (3, 1, 0),
     'location': 'File > Import-Export',
     'description': 'Import-Export as glTF 2.0',

io_scene_gltf2/blender/exp/gltf2_blender_extract.py

@@ -526,18 +526,11 @@ def __get_uvs(blender_mesh, uv_i):
 
 
 def __get_colors(blender_mesh, color_i):
-    layer = blender_mesh.vertex_colors[color_i]
     colors = np.empty(len(blender_mesh.loops) * 4, dtype=np.float32)
-    layer.data.foreach_get('color', colors)
+    layer = blender_mesh.vertex_colors[color_i]
+    blender_mesh.color_attributes[layer.name].data.foreach_get('color', colors)
     colors = colors.reshape(len(blender_mesh.loops), 4)
-
-    # sRGB -> Linear
-    rgb = colors[:, :-1]
-    not_small = rgb >= 0.04045
-    small_result = np.where(rgb < 0.0, 0.0, rgb * (1.0 / 12.92))
-    large_result = np.power((rgb + 0.055) * (1.0 / 1.055), 2.4, where=not_small)
-    rgb[:] = np.where(not_small, large_result, small_result)
-
+    # colors are already linear, no need to switch color space
     return colors
 
 

io_scene_gltf2/blender/imp/gltf2_blender_mesh.py

@@ -250,9 +250,6 @@ def do_primitives(gltf, mesh_idx, skin_idx, mesh, ob):
     for uvs in loop_uvs:
         uvs_gltf_to_blender(uvs)
 
-    for cols in loop_cols:
-        colors_linear_to_srgb(cols[:, :-1])
-
     # ---------------
     # Start creating things
 
@@ -292,7 +289,7 @@ def do_primitives(gltf, mesh_idx, skin_idx, mesh, ob):
                   "reached.")
             break
 
-        layer.data.foreach_set('color', squish(loop_cols[col_i]))
+        mesh.color_attributes[layer.name].data.foreach_set('color', squish(loop_cols[col_i]))
 
     # Skinning
     # TODO: this is slow :/
@@ -468,16 +465,6 @@ def colors_rgb_to_rgba(rgb):
     rgba[:, :3] = rgb
     return rgba
 
-
-def colors_linear_to_srgb(color):
-    assert color.shape[1] == 3  # only change RGB, not A
-
-    not_small = color >= 0.0031308
-    small_result = np.where(color < 0.0, 0.0, color * 12.92)
-    large_result = 1.055 * np.power(color, 1.0 / 2.4, where=not_small) - 0.055
-    color[:] = np.where(not_small, large_result, small_result)
-
-
 def uvs_gltf_to_blender(uvs):
     # u,v -> u,1-v
     uvs[:, 1] *= -1