[Gmsh] Strange meshing behaviour

[Christophe Geuzaine]

Hi Peter,

Interesting. This seems to be a problem with the generation of the geometry, not the meshing.

Attached is the .brep file of the buggy surface (debugSurface.brep):

- the OpenCASCADE representation is wrong (see attached picture of the OpenCASCADE-produced STL triangulation), which seems to indicate that the parametric representation is wrong

- the surface also leads to an incorrect mesh with Gmsh 4.4.1

I would suggest to send the "debugSurface.brep" file to the OpenCASCADE developers for further analysis?

Christophe

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> On 11 Mar 2020, at 12:40, Peter Johnston <p.johnston at griffith.edu.au> wrote:
> 
> Hello,
> 
> I have just observed some strange behaviour with my python script running gmsh. Attached is a cut down version of a larger script that used to work under gmsh 4.4.1. This script creates a 3D volume using OCC and contains multiple surfaces. When I mesh the surface (ie use the 2D meshing button on the gui) surface number three gives some strange results; so strange that I cannot create a volume mesh. I have also attached a picture of the mesh on surface 3, indicating the places where the mesh is misbehaving. I am currently using gmsh 4.5.4.
> 
> (Please note that I had to change the file extension to escape institutional spam filters. It is really a python script.)
> 
> Any insights would be much appreciated.
> 
> Thanks very much,
> 
> Peter.
> 
> Associate Professor Peter Johnston (FAustMS, FIMA)
> School of Environment and Science
> Griffith University | Nathan | QLD 4111 | Technology (N44) Room 3.19
> T +61 7 373 57748| F +61 7 373 57656 Email p.johnston at griffith.edu.au
> <gmsh-prob.png><cap_cut.txt>_______________________________________________
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? 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine