CGAL users discussion list

[Richard Downe <>]

I have a program that uses Nef_Polyhedron_3 to merge several disjoint 
structured grids, and then remeshes the surface using a delaunay 
triangulation.  Out of several surfaces I'm preparing, one has 
stubbornly refused to mesh.  After a day or so of tweaking the 
parameters, I generated .off files to permit me to visualize the 
intermediate surface and troubleshoot.

In examining the .off version of the troublesome surface, I noticed that 
there are several degenerate triangles (e.g., 2 coincident vertices, and 
therefore a zero-valued normal).  I'm assuming this has to do with 
distances in the EPECK kernel that are too small to represent in the 
EPICK kernel, which therefore get rounded off.

My question is this: does a filter exist which can remove these 
triangles *prior* to casting the polyhedron to an EPICK kernel?  Or am I 
on my own (e.g., either filtering the inexact kernel version and simply 
erasing the degenerate triangles, or alternately, filtering the exact 
one and merging any triangle with a sufficiently high aspect ratio with 
an adjacent triangle in the hopes of avoiding degeneracy post-cast)?

Any help would be very much appreciated.

-Richard