[Gmsh] surface mesh coarsening

[Christophe Geuzaine]

> On 18 Mar 2020, at 08:56, Hans Dierckx <h.dierckx at kuleuven.be> wrote:
> 
> Dear all, 
>  
> Can someone explain me how to use gmesh to coarsen a closed surface mesh? I attach a simple geometry as test data.
> I tried in vain in the GUI to put ‘options > mesh > element size’ to a value bigger than one.
> The data I want to apply it to is a heart geometry which has originally 10^6 vertices and 5 10^5 faces, which should be reduced to approx. 500 faces.
>  

You should save your initial model as a mesh, not a CAD model; for example you can save your input mesh as a STL file. (Beware that your mesh should be correctly oriented - it's not the case for the CAD you sent.)

You can the reparametrize the mesh, which will create a multi-patch, discrete geometry that you can remesh. On the command line:

> gmsh file.stl -reparam 180
> gmsh file.msh -clcurv 10 -2

See tutorial/t13.geo for the same workflow in a .geo script, or tutorial/python/t13.py or demos/api/remesh_stl.py for the same using the Python API.

Christophe


> Thank you very much for your assistance.
>  
> Hans Dierckx
> Leuven University
>  
>  
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine