fix(vertex colors): support new color attributes and handle multiple …

…domains (#215)

Vertex colors are now handled using `color_attributes`, replacing the deprecated `vertex_colors`. This update adds support for both CORNER and POINT domains.
https://docs.blender.org/api/current/bpy.types.Mesh.html#bpy.types.Mesh.vertex_colors

fixes: #204

addon/i3dio/node_classes/shape.py

@@ -192,7 +192,7 @@ def process_subsets(self, mesh) -> None:
             subset.first_index = next_index
             next_vertex, next_index = self.process_subset(mesh, subset)
 
-    def process_subset(self, mesh, subset: SubSet, triangle_offset: int = 0) -> tuple[int, int]:
+    def process_subset(self, mesh: bpy.types.Mesh, subset: SubSet, triangle_offset: int = 0) -> tuple[int, int]:
         self.logger.debug(f"Processing subset: {subset}")
         for triangle in subset.triangles[triangle_offset:]:
 
@@ -202,13 +202,23 @@ def process_subset(self, mesh, subset: SubSet, triangle_offset: int = 0) -> tupl
             for loop_index in triangle.loops:
                 blender_vertex = mesh.vertices[mesh.loops[loop_index].vertex_index]
 
-
                 # Add vertex color
                 vertex_color = None
-                if len(mesh.vertex_colors):
-                    # Get the color from the active layer or first layer, since only one vertex color layer is supported in GE
-                    color_layer = mesh.vertex_colors.active if mesh.vertex_colors.active is not None else mesh.vertex_colors[0]
-                    vertex_color = color_layer.data[loop_index].color
+                if len(mesh.color_attributes):
+                    # Use the active color layer or fallback to the first (GE supports only one layer)
+                    color_layer = mesh.color_attributes.active_color or mesh.color_attributes[0]
+
+                    match color_layer.domain:
+                        case 'CORNER':
+                            # Color data is stored per corner/loop
+                            vertex_color = color_layer.data[loop_index].color_srgb
+                        case 'POINT':
+                            # Color data is stored per vertex
+                            color_vertex_index = mesh.loops[loop_index].vertex_index
+                            vertex_color = color_layer.data[color_vertex_index].color_srgb
+                        case _:
+                            self.logger.warning(f"Incompatible color attribute {color_layer.name}: "
+                                                f"domain={color_layer.domain}, data_type={color_layer.data_type}")
 
                 # Add uvs
                 uvs = []