ERROR: CGAL error in CGAL_Nef_polyhedron3(): CGAL ERROR: assertion violation! Expr: e->incident_sface() != SFace_const_handle() File: /usr/local/include/CGAL/Nef_S2/SM_const_decorator.h Line: 326 this is a simple STL file with a difference cube subtracting part of it, thinking it might be a "dirty" STL file, I tried rather successfully with a small project of my own that uses jCSG (https://github.com/chriscamacho/JcsgFX another commit pending!) and I was able to import and boolean the STL just fine. I've had very little joy at all with CGAL and any kind of boolean operation with CGAL, I'd like to understand what this particular assertion means as I have seen it more than once! Chris

> I'd like to understand what this particular assertion means Short story, a bad STL. Self intersecting. e is a halfedge, the face on the other side of that edge equals the face on this side of the edge. You can see the CGAL code (a version, not necessarily the one in your version of OpenSCAD) here <https://searchcode.com/file/118734730/include/CGAL/Nef_S2/SM_const_decorator.h#l-8> - line 319. If you want to share the STL, I'll have a look at it. ----- 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/CGAL-what-does-this-mean-tp21992p22005.html Sent from the OpenSCAD mailing list archive at Nabble.com.