CGAL users discussion list

[Chris Hamilton <>]

> The .off file format can not represent all Nef3 polyhedra
> objects.  In particular, if you have a surface with one
> or more holes in it, .off format can not represent it.

Makes sense.  However, the intersection of any two closed and bounded
polyhedra should itself be a closed and bounded polyhedron, which should
be representable by the .off file format.  Whatever the degeneracy
implied by "intersecting constraints", it should be representable in
Polyhedron_3 objects (and hence .off files) somehow, no?

My actual question is this: what does 'intersecting constraints' mean,
and why is not representable by Polyhedron_3 objects (and hence .off
files)?  Is this something that is an error, is this something that is
possible but not yet implemented, or is this something that can't be
implemented for some reason?

> There is a file format called .nef3 that can represent all
> .nef3 objects.  The demo program ../dem/Nef_3/nef_3_homgeneous
> can read .nef3 objects.  It used to be able to write .nef3
> objects but that code was removed for some reason.  I have
> a snippet of code that adds back the "savenef3" command
> to the demo program if you are interested.

Are these files viewable somehow, or is only the internals of CGAL that
can make use of them?

Chris