[Gmsh] node positions on B-splines

[Eiser, Sebastian]

I cannot open your file with my svn version...
Error   : Line Loop 17 is wrong
Error   : Line Loop 18 is wrong
Error   : Line Loop 19 is wrong
Error   : Line Loop 20 is wrong

Anyways, have you tried using the 'Layers' command in your extrusion? It will produce prisms. 

Unfortunately, there is also a known problem with extruded layers when refining:
https://geuz.org/trac/gmsh/ticket/184 (gmsh:gmsh)



-----Original Message-----
From: gmsh-bounces at ace20.montefiore.ulg.ac.be [mailto:gmsh-bounces at ace20.montefiore.ulg.ac.be] On Behalf Of Rene Schneider
Sent: Thursday, February 14, 2013 2:49 PM
To: gmsh at geuz.org
Subject: [Gmsh] node positions on B-splines

Hi

First of all, thanks for providing this great software.

I'm trying to mesh a 3D geometry defined by extruding B-spline segments, see attached example.

I noticed that nodes accumulate close to the lines that originate from extruding the end-points of the B-splines, resulting in extremely thin surface triangles. Thus fairly bad tets are generated in the 3d mesh in these regions.

Even worse: if the mesh is refined, the surface triangles are "sucked" 
into this region, degenerating to zero surface area. Correspondingly tets result, with zero volume.

I presume this problem could result from an error in distance measurement on the surface.

If I use splines instead of B-splines, the problem is gone.

Any help is appreciated, I really need those B-splines.

I'm using
$ gmsh --version
2.6.1
under Linux.


Rene