[Gmsh] Zero volume tets
cgeuzaine at uliege.be
Tue May 12 13:28:43 CEST 2020
> 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.
> You'll find all necessary files in the attached archive.
> gmsh mailing list
> gmsh at onelab.info
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
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