CGAL users discussion list

[Laurent Saboret <>]

Dear Laurent R.,

From time to time, the Surface Mesher prompts the same error when contouring the APSS 
implicit surface, e.g.:
https://cgal.geometryfactory.com/CGAL/Members/testsuite/CGAL-3.5-I-99/Surface_reconstruction_points_3/TestReport_lrineau_i686_Linux-2.6_g++-4.1.2_CentOS-5.1-O2.gz

Does this ring any bell?

Best regards,
Laurent S.


Andreas Fabri a écrit :
> Hi Shamyl,
>
> as you write the problem is not so much related to mesh simplification
> but to the incremental builder for polyhedral surfaces, so the subject
> line is rather misleading.
>
> No idea how your input looks like, but you get these kind of exceptions
> if your surface is non-manifold, that is there are more than two faces
> sharing an edge.  You get this for example when you have two tetrahedra
> which share just one edge.  So things look ok, but they are not, that's
> why OpenGL just works.
>
> Besides, instead of marching cubes + mesh simplification you might
> give the Surface Mesher  a try. It generates quality triangles for
> iso-levels in grey level images:  http://www.cgal.org/Pkg/SurfaceMesher3
> In the polyhedron demo it is also used as a remesher for an input
> surface.
>
> best regards,
>
> andreas
>
>
>
> Shamyl Zakariya wrote:
> > Hello!
> >
> > I've been using CGAL to simplify meshes created with the Marching
> > Cubes algorithm. Specifically, I'm using the algorithms described
> > here:
> >
> > http://www.cgal.org/Manual/3.4/doc_html/cgal_manual/Surface_mesh_simplification/Chapter_main.html 
> >
> >
> > So far, it works wonderfully, 90% of the time. The other 10% of the
> > time, CGAL throws an during the construction of the surface from my
> > geometry:
> >
> > --------
> >
> > CGAL::Polyhedron_incremental_builder_3<HDS>::
> > lookup_halfedge(): input error: facet 851 has a self intersection at 
> > vertex 473.
> > CGAL error: assertion violation!
> > Expr: check_protocoll == 0
> > File: /usr/local/include/CGAL/Polyhedron_incremental_builder_3.h
> > Line: 198
> > Explanation:
> > terminate called after throwing an instance of 
> > 'CGAL::Assertion_exception'
> >   what():  CGAL ERROR: assertion violation!
> > Expr: check_protocoll == 0
> > File: /usr/local/include/CGAL/Polyhedron_incremental_builder_3.h
> > Line: 198
> >
> > -------
> >
> > Note, this is happening while *creating* the surface, not during
> > simplification. I assume what's happening is that my mesh data created
> > by marching cubes has some kind of "problem" with it. But
> > superficially Im fairly confident of my mesh data. Marching Cubes is
> > an established algorithm, and my mesh data works fine for collision
> > detection and rendering via OpenGL without any obvious weirdnesses.
> >
> > Here's the code I'm using -- most of it is boilerplate converting from
> > my geometry storage to CGAL's, and visa versa.
> >
> > http://pastie.org/489281
> >
> > Specifically, CGAL dies on line 94
> >
> > For what it's worth, I'm using CGAL  3.3.1 ( I didn't realize there
> > was a new release until I went to cgal.org to sign up for the mailing
> > list )
> >
> > Any suggestions would be greatly appreciated. I've evaluated several
> > mesh simplification algorithms, and CGAL's consistently produces the
> > best output ( when my data isn't problematic! )
> >
> > Thanks,

--
Laurent Saboret
INRIA Sophia-Antipolis
Project GEOMETRICA
(33) 4 97 15 53 09