xmlNodePtr mesh_node = xmlNewChild(node, 0, BAD_CAST "mesh",0);
xmlNewProp(mesh_node, BAD_CAST "name", BAD_CAST _collection->getName().c_str());
xmlNodePtr mesh_node = xmlNewChild(node, 0, BAD_CAST "mesh",0);
xmlNewProp(mesh_node, BAD_CAST "name", BAD_CAST _collection->getName().c_str());