[Gmsh] detect negative jacobians

Bernd Hahnebach gmsh at b75.ch
Wed Mar 30 07:30:12 CEST 2016

Thanks Christophe!

I got the problem of the high order meshes by reading a big part of  
the paper. :-) :-)  Is there any user documentation or an example how  
to use the HighOrderTools around?

Just to get it the right way done. How does it work in the gui?

- Load the geometry (in my case a BRep)
- make the adjustments on Tools --> Options --> Geometry and Mesh -->  
one of them is 2nd order mesh
- In GMSH Tree press Mesh 1D, 2D, 3D
- on 3D I get negative Jacobians if the mesh order in options is set to two
- do not use any optimization, do not use the order buttons (mesh is  
2nd order already)
- open HighOrderTools
- Generate 2nd order vertices
- Regularize with given values

- Or do I have to start with a 1st order mesh and use Generate 2nd  
order vertices on a 1st order mesh?
- Should any of the optimizations be done before the HighOrderTools?

kind regards bernd

Zitat von Christophe Geuzaine <cgeuzaine at ulg.ac.be>:

>> On 24 Mar 2016, at 19:06, Christophe Geuzaine <cgeuzaine at ulg.ac.be> wrote:
>>> On 24 Mar 2016, at 12:27, Bernd Hahnebach <gmsh at b75.ch> wrote:
>>> What is the recommended way to avoid such negative jacobians?  
>>> Attached the geometry of the mesh above.
> And to avoid such negative jacobians, you can use the "High order  
> tools" (in the Mesh menu). This is still experimental, but works  
> quite well. The algorithms are described (in part) in
> T. Toulorge, C. Geuzaine, J.-F. Remacle, J. Lambrechts. Robust  
> untangling of curvilinear meshes. Journal of Computational Physics  
> 254, pp. 8-26, 2013.  
> http://gmsh.info/doc/preprints/gmsh_untangling_preprint.pdf
> Christophe
> --
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine
> Tetrahedron V, July 4-5 2016: http://tetrahedron.montefiore.ulg.ac.be
> Free software: http://gmsh.info | http://getdp.info | http://onelab.info

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