[Gmsh] structured and unstructured meshes bug

[Michel Aubourg]

It's now more clear for me, thank you again and, yes, gmsh is a very powerfull 
tool.

Le Mercredi 22 Mars 2006 12:59, vous avez écrit :
> Michel Aubourg wrote:
> > Hi Christophe,
> >
> > Thank you very much for this answer.
> >
> > I did't find that in the documentation (the HTML one build from sources
> > distribution) where we can read that the surfaces are meshed before the
> > volumes and that the so generated triangles are forced to be faces of the
> > tetrahedra created later.
> > I understood that the mesh of an internal surface was uniquely defined,
> > which is not the case; I suggest to up-to-date this documentation to
> > avoid disapointment for future users.
>
> I'll add something in the docs. Note that this can *only* happen when
> you try to mix structured and unstructured volume meshes. In the usual
> case (unstructured volume meshes, with or without structured surface
> meshes), this will *never* happen.
>
> > In another way I join a very short file for which the use of "isotropic"
> > gives of course bad mesh and "netgen" crashes; what is wrong ?
>
> As I said in my last email, the "netgen" algorithm requires the boundary
> of the volume to be oriented with outward pointing normals. This is not
> automatically ensured by gmsh at the moment, so you have to do it by
> hand. See attached file for a correct definition of your geometry.
>
> > I used gmsh 1.60.1 and 1.64.1 both compiled alternatively with gcc-3.4.3,
> > gcc-3.3.6 and gcc-4.0.1.
> >
> > Best,
> >
> > Michel
> >
> > Le Mercredi 22 Mars 2006 02:11, vous avez écrit :
> >> Michel Aubourg wrote:
> >>> Re-bonjour,
> >>>
> >>> Avec le fichier joint cela ira mieux.
> >>
> >> Hi Michel - Unfortunately, that's inherent to the Delaunay technique as
> >> implemented in the default "isotropic" algorithm. You can use the
> >> combined Delaunay+advancing front technique from the "netgen" algorithm
> >> to fix this. (Add e.g. "Mesh.Algorithm3D = 4;" at the beginning of your
> >> file; beware that your volume boundary has to be defined with exterior
> >> pointing normals when using this algorithm.)
> >>
> >> Best,
> >>
> >> Christophe

-- 
Michel AUBOURG
Département MINACOM
XLIM
123, avenue Albert Thomas
87060 LIMOGES
FRANCE
Tel: +33 (0)5 55 45 73 76
Email: michel.aubourg at xlim.fr
http://www.xlim.fr