PixelMaterialMap Node1 PixelMaterialMap + PixelMaterialMap() + addMaterial() + getMaterial() Node2 std::map< Key, std ::string > Node2->Node1 -m_matmap Node3 std::string Node3->Node2 +elements Node5 PixelMaterialMap::Key + layerdisk + typenum + Key() + operator<() Node3->Node5 +volumeName Node4 std::basic_string< char > Node4->Node3 Node5->Node2 +keys