http://www.graphisoft.com/ftp/techsupport/documentation/developer_docs/BasicLibraryDoc/16/Window-Macros/PolygonOperations.html#title33

http://paulbourke.net/geometry/

http://archicad-talk.graphisoft.com/viewtopic.php?t=41635

!TEST    http://forum.cadstudio.ru/index.php?topic=26281.msg169091#msg169091