That region is the post tessellation version of this line on the side generated by CGAL. [image: image.png] I presume that is a very long thin polygon that, when its vertices get snapped, starts to self intersect and then breaks the tessellation algorithm. On Thu, 28 May 2020 at 05:11, OzAtMichael <oz.at.michael@gmail.com> wrote: > > Possibly the gross flipped triangle is caused by the tessellation from > polygon to triangles going wrong when there are small flipped triangles, > just a guess. > > > > Getting warmer. > > > > With add_rotate=7, flushed-F6, export; STL is attached. > > > > There is z-fighting in this region. > > > > This is slightly moved. > > > > I then selected the two triangles (black is selected-backface) > > > > I then remove the two faces. > > > > Showing correctly oriented faces. Plus other issues in the region. > > > > So it is not just small-numbers. > > > > Meshlab > > > > Note the two arrows there is no vertex there (488 is on the other side), > there are 4-6 overlapping triangles, one or two inverted. > > There are no small triangles that I can see. > > > > > > > > > > > > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> Virus-free. > www.avg.com > <http://www.avg.com/email-signature?utm_medium=email&utm_source=link&utm_campaign=sig-email&utm_content=emailclient> > <#m_-8453963217785480828_DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2> > _______________________________________________ > OpenSCAD mailing list > Discuss@lists.openscad.org > http://lists.openscad.org/mailman/listinfo/discuss_lists.openscad.org >