Oh, that makes sense. So it's really caused by invalid arguments to polyhedron. We should change polyhedron to report when you pass illegal arguments. On 17 March 2016 at 19:49, Torsten Paul <Torsten.Paul@gmx.de> wrote: > On 03/18/2016 12:32 AM, unkerjay wrote: > > 1) Curious what led to the two functions you refer to as the problem > > Trial and error? Or something more methodical? > > > The import() statements cause the issue because those are the > only thing that force actual mesh calculation by the difference(). > Without, there is no CGAL call at all. Even just placing a cube() > into the write functions produces the same effect. > > I think the reason is that the model (the polyhedron) is not > a solid object but just an illusion and so it only works in > preview mode. > > ciao, > Torsten. > > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > >

@Doug: I'm not generalizing. Sometimes it shows up. Sometimes it doesn't. When it DOES (and it has on at least one other polyhedra), I've tried removing this code and that fixed it. It may not always be the culprit. But, there's no real harm in trying and seeing what happens. If it resolves the problem, fine. If not, well, one less thing to try. -- View this message in context: http://forum.openscad.org/Previews-but-doesn-t-render-tp16511p16568.html Sent from the OpenSCAD mailing list archive at Nabble.com.

Well, the source code for the Ditrigonal Dodecacronic Hexecontahedron that you posted was automatically generated by Kit Wallace's program, based on polyhedron data from http://dmccooey.com/polyhedra/. In fact, the polyhedron was generated automatically, on the fly, by accessing that URL on Kit's web site. So it's reasonable to guess that Kit hasn't actually tested all of the possible scad scripts that his program can generate. Certain kinds of errors in the polyhedron data cause the polyhedron itself to apparently preview and render okay, but when you attempt a CSG operation (like difference()) then you get an error message or nonsense results. I'm assuming that Torsten is right. That means some of the polyhedron data files on dmccooey's web site are "not 2-manifold", which is a technical term meaning bad. The bug is actually in dmccooey's data, although it's also bad that OpenSCAD sucks at reporting bad arguments to polyhedron(). On 18 March 2016 at 15:12, unkerjay <unkerjay@centurylink.net> wrote: > @Doug: > > I'm not generalizing. Sometimes it shows up. Sometimes it doesn't. > > When it DOES (and it has on at least one other polyhedra), I've tried > removing > this code and that fixed it. > > It may not always be the culprit. But, there's no real harm in trying and > seeing > what happens. > > If it resolves the problem, fine. > > If not, well, one less thing to try. > > > > -- > View this message in context: > http://forum.openscad.org/Previews-but-doesn-t-render-tp16511p16568.html > Sent from the OpenSCAD mailing list archive at Nabble.com. > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org > > >

Been a LONG time, it probably applies here: GIGO (bad data, bad outcome - (BDBO?) -- View this message in context: http://forum.openscad.org/Previews-but-doesn-t-render-tp16511p16571.html Sent from the OpenSCAD mailing list archive at Nabble.com.

On Fri, 18 Mar 2016 14:56:07 -0700 (MST) unkerjay <unkerjay@centurylink.net> wrote: > Been a LONG time, it probably applies here: > > GIGO Garbage in, gospel out? <grin/> > (bad data, bad outcome - (BDBO?) > > > > -- > View this message in context: > http://forum.openscad.org/Previews-but-doesn-t-render-tp16511p16571.html > Sent from the OpenSCAD mailing list archive at Nabble.com. > > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org -- Reality is just a convenient measure of complexity. -- Alvy Ray Smith