[Gmsh] Zero volume tets

[Karin&NiKo]

Thanks for the tip Christophe!
"Mesh.Algorithm3D = 10;" is indeed faster and produces less elements.

Nicolas

Le mar. 12 mai 2020 à 13:28, Christophe Geuzaine <cgeuzaine at uliege.be> a
écrit :

>
>
> > On 12 May 2020, at 11:49, Karin&NiKo <niko.karin at gmail.com> wrote:
> >
> > Dear Gmsh Gurus,
> >
> > I am facing some troubles with a brep CAD I am trying to mesh with Gmsh.
> > If I try the meshing default settings, the mesh is being built and Gmsh
> is proud to announce that no illegal tet stand in the mesh. *But* if I
> simply run "gmsh -check", Gmsh admits that zero volume tets stay in the
> mesh. So it is unusable for computation.
>
> There maybe too many messages, but the optimizer indeed reports that there
> are 6 tets below the quality threshold in volume 2 with the default algo
> (we should issue a warning if the quality is indeed approaching zero):
>
> Info    : Optimizing volume 2
> Info    : Optimization starts (volume = 3.52969e+07) with worst = 0 /
> average = 0.757222:
> Info    : 0.00 < quality < 0.10 :       212 elements
> Info    : 0.10 < quality < 0.20 :       362 elements
> Info    : 0.20 < quality < 0.30 :       166 elements
> Info    : 0.30 < quality < 0.40 :       222 elements
> Info    : 0.40 < quality < 0.50 :       287 elements
> Info    : 0.50 < quality < 0.60 :       765 elements
> Info    : 0.60 < quality < 0.70 :      3802 elements
> Info    : 0.70 < quality < 0.80 :      7720 elements
> Info    : 0.80 < quality < 0.90 :      4721 elements
> Info    : 0.90 < quality < 1.00 :      4214 elements
> Info    : 321 edge swaps, 0 node relocations (volume = 3.52969e+07): worst
> = 0 / average = 0.765757 (Wall 0.022079s, CPU 0.022s)
> Info    : 338 edge swaps, 0 node relocations (volume = 3.52969e+07): worst
> = 0 / average = 0.765884 (Wall 0.0357411s, CPU 0.035583s)
> Info    : 339 edge swaps, 0 node relocations (volume = 3.52969e+07): worst
> = 0 / average = 0.765909 (Wall 0.0503662s, CPU 0.050068s)
> Info    : 6 ill-shaped tets are still in the mesh
>
>
> > I have succeeded in producing a correct mesh by using the Frontal 3D
> algorithm (Mesh.Algorithm3D = 4;).
> > Perhaps a check of the presence of zero volume elements could be an
> interesting enhancement.
>
> You can also try
>
> Mesh.Algorithm3D = 10;
>
> which is (here a bit) faster.
>
> Christophe
>
>
> > You'll find all necessary files in the attached archive.
> >
> > Regards,
> > Nicolas
> > <foo.tar.gz>_______________________________________________
> > gmsh mailing list
> > gmsh at onelab.info
> > http://onelab.info/mailman/listinfo/gmsh
>
> —
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine
>
>
>
>
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