Hi Alexander, Good to see you worked it out. > The error message happens only the first time I render. If I re-render, > then nothing happens, and nothing shows up on screen, and STL generation > says "Current top level object is empty." That's because F6 CGAL caches, and with an error the results are empty, but it still has been evaluated so doesn't try again. Either change something or do Design/Flush_caches then re-render. BTW, your post is still flagged as "This post has NOT been accepted by the mailing list yet", so nobody gets it unless they look. You need to subscribe to the mailing list <http://forum.openscad.org/mailing_list/MailingListOptions.jtp?forum=1> , and respond to the registration email. ----- Admin - PM me if you need anything, or if I've done something stupid... Unless specifically shown otherwise above, my contribution is in the Public Domain; to the extent possible under law, I have waived all copyright and related or neighbouring rights to this work. Obviously inclusion of works of previous authors is not included in the above. The TPP is no simple “trade agreement.” Fight it! http://www.ourfairdeal.org/ time is running out! -- View this message in context: http://forum.openscad.org/ERROR-CGAL-error-in-CGALUtils-applyBinaryOperator-tp19585p19589.html Sent from the OpenSCAD mailing list archive at Nabble.com.