[Gmsh] Multilevel mesh partition element interface quality

[Andre Nicolle]

Dear gmsh user group

I have been struggling with meshing a stl file of a human mesh. The stl 
surface is in good shape with a closed surface which when loaded into 
gmsh and meshed using the procedure outlined in 
https://geuz.org/trac/gmsh/wiki/STLRemeshing forms a three-dimensional 
mesh. Unfortunately the tetrahedron element quality is very poor. On 
further investigation we found that this was caused by poor quality 
elements on the 2D surface after the surface was remeshed. We tried 
using  Mesh.Algorithm: 1 = MeshAdapt, 2=Automatic, 5=Delaunay, 6=Frontal 
and found that in general Frontal gave us the best elements which were 
all very good quality except on the interface between the multilevel 
mesh partitions.  Information on the partition stage of 2-D meshing is 
given below.

Attached is a picture showing the line-up of poor quality elements 
around the waist of the human. Nearly all the other 2-D triangular 
elements have a mesh quality indicator gamma > 0.5, however elements on 
theinterface have gamma approximately 0.03 which we believe is where the 
3-D mesh problem is starting from.

Could somebody give us some advice on how best to solve this problem as 
I imagine it is a mistake on our implementation. If further information 
is required please let me know what would be helpful to diagnose the 
problem.

Any help would be gratefully received

Andre

gmsh version 2.6.1

Info    : Meshing surface 200 (Compound surface, MeshAdapt)
Warning : Wrong topology: Genus=0, Nb boundaries=0, AR=1
Info    : -----------------------------------------------------------
Info    : --- Split surface 200 in 2 parts with Multilevel Mesh partitioner
Info    : Building graph...
Info    : Partitioning graph...
Info    : Launching Chaco graph partitioner
Info    : Done partitioning graph
Info    : *** Mesh partition: level (1-0) is ZERO-GENUS (AR=5, NB=1)
Info    : *** Mesh partition: level (1-1) is ZERO-GENUS (AR=4, NB=1)
Info    : Multiscale Partition SUCCESSFULLY PERFORMED : 2 parts (3.26 s)
Info    : *** Starting parametrize compounds:
Info    : Parametrize Compound Line (2) = 1 discrete edge
Info    : Parametrize Compound Surface (203) = 201 discrete face
Info    : Parametrizing surface 203 with 'convex map'


Warning : Mesh generation error summary
Warning :     1 warning
Warning :     0 errors
Warning : Check the full log for details


-------------- next part --------------
A non-text attachment was scrubbed...
Name: test.jpg
Type: image/jpeg
Size: 164119 bytes
Desc: not available
URL: <http://www.geuz.org/pipermail/gmsh/attachments/20121031/b145e2ae/attachment.jpg>