CGAL users discussion list

["Sebastien Loriot (GeometryFactory)" <>]

Qianqian Fang wrote:
> On 03/18/2011 04:09 AM, Sebastien Loriot (GeometryFactory) wrote:
> > Christoph Weber wrote:
> > > Hi,
> > >
> > > I'm working a similar subject. If you are just looking for a tool, I
> > > would emphasize TetGen. It is open source, dokumented and focused on
> > > FE-Meshes. 
> > By curiosity, why do you prefer using TetGen than CGAL's Mesh_3 to
> > generate FE-Meshes?
>
> I've been using both CGAL and tetgen in my research and I noticed
> that CGAL 3D polyhedral mesher is very unstable for most of my inputs.
>
> Here is a simple example, the input mesh is a triangular surface
> mesh extracted from a binary CT image of a rat head. The OFF format
> and POLY format files can be accessed from
>
> http://nmr.mgh.harvard.edu/~fangq/temp/post_extract.off
Your off file contains triangles that are not consistently oriented
to describe a polyhedron. You need to reorient triangles.

If you use the Polyhedron demo of CGAL, do:
"Operations -> Orient polygon soup"
To produce a 3D mesh you can then do:
Save in back to an off file and reload it.
Then do:
"Operation -> Create a tetrahedral mesh"
 or directly use your code.



> http://nmr.mgh.harvard.edu/~fangq/temp/post_vmesh.poly
>
> both files contain the same mesh. Using the .poly file with
> tetgen, I can get a nice 3D tetrahedral mesh, but with the
> CGAL polyhedral mesher (examples/Mesh_3), the program aborted
> when processing the OFF file. This behavior can be reproduced
> from CGAL 3.5 to the latest 3.8 beta. The polyhedral mesher
> failed for almost all tested surface meshes except those shipped
> with CGAL. Not sure what had caused the problem.
>
> The robustness of CGAL 3D image mesher is better, but there is
> one issue that keeps it from perfect for general-purpose use.
> I summarized it in this post
>
> https://lists-sop.inria.fr/sympa/arc/cgal-discuss/2011-03/msg00067.html
You'll get an answer to this one soon.

S.

> it would be great if someone can comment on this.
>
> Qianqian
>
>
> > The Polyhedron demo has a plugin that allows to generate 3D meshes from
> > an off file (Operations->Create a tetrahedral mesh).
> >
> > S.
> >
> > > regs, Christoph
> > > Am Donnerstag, den 17.03.2011, 12:53 -0500 schrieb Fabio Casado Ruiz:
> > > > Hi. I'm studying several tools and libraries for mesh generation to 
> > > > use in Finite element Analysis. Has anyone used CGAL for this 
> > > > purposes or has any knowledge where to read about its pros and cons 
> > > > for this purpose???
> > > > Thanks a lot..
> > > > F.