message: Face ids per obj group
diff: @@ -244,6 +244,8 @@ static void load_obj(
  objs.push_back(std::make_shared<sg::surface_properties>());
  objs.back()->add_child(std::make_shared<sg::triangle_mesh>());
  + face_id = 0;
  +
  surf = std::dynamic_pointer_cast<sg::surface_properties>(objs.back());
  tm = std::dynamic_pointer_cast<sg::triangle_mesh>(surf->children().back());
  