CGAL users discussion list

["Wayne C. Gramlich" <>]

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.

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.

-Wayne

Laure Guicherd wrote:
> Hi everyone,
> Is there someone on this ? Because I am meeting the exact same issue. 
> Everything else is working nicely, but sometimes it fails this way, and 
> i have absolutely no idea of the reason for this :(
> My meshes are closed and valid, with no self-intersections or "flat" faces.
>
> Any idea will be helpful, thank you very much !
>
> Laure Guicherd
>
> Chris Hamilton wrote:
> > Previously, I've used the GNU triangulated surface library (libgts), but
> > I've been having precision issues with that, and am now trying to work
> > with CGAL.  I'm trying to compute the intersection between two closed
> > and bounded polyhedra.
> >
> > I'm using Nef_polyhedron_3 with the
> > Exact_predicates_exact_constructions_kernel.  The polyhedra are being
> > laoded as .off files through the Polyhedron_3 object, converted to
> > Nef_polyhedron_3 objects, and the intersection computed.  Afterwards,
> > the result is converted back to a Polyhedron_3, and output as an .off 
> > file.
> >
> > All is largely well, except sometimes the process fails with the
> > following message:
> >
> >  sorry, this triangulation does not deal with
> >  intersecting constraints
> >
> > This error occurs during conversion back to Polyhedron_3.  What exactly
> > does this error mean?  Is there a way I can get the results out as an
> > .off file?
> >
> > And on a slightly related question: is there a way to compute the 3d
> > volume of a closed polyhedron in CGAL?  Either via the Nef_polyhedron_3
> > data-structure, or the Polyhedron_3, as I'd always be dealing with
> > closed meshes.
> >
> > Regards,
> >
> > Chris
> >
> >