<https://forum.vectorworks.net/index.php?/topic/48459-rendering-viewport-turns-everything-black/#comment-246208>
<http://www.w3.org/1999/02/22-rdf-syntax-ns#type>
<https://forum.vectorworks.net/index.php?/topic/48459-rendering-viewport-turns-everything-black/&tab=comments#comment-276850>