[Gmsh] STL Mesh generation surfaces with inward normalnot meshed?!

[Christophe Geuzaine]

> On 12 May 2020, at 17:50, Zuheyr Alsalihi <alsalihi at vki.ac.be> wrote:
> 
> Dear colleagues,
> 
> I could not easily describe the problem.
> 
> A rectangular slab step file that I have generated, attached CG1.step, shows the top and bottom surfaces inward normal.
> I am not able to reverse this.
> But the surface is there, see Pic1.png. When I create an STL mesh with GMSH gmsh-4.5.6-Linux64/bin/gmsh
> these 2 surfaces are not meshed. Can you please help me understand and solve this problem?

Somehow OpenCASCADE badly translates surface 5 in the STEP file. See attached .brep of the offending surface: all point evaluations within the surface are (wrongly) evaluated on a plane parallel to the surface, but translated.

You should report this bug to the OpenCASCADE developers and attach the STEP file.

Christophe

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> Many thanks for reading.
> Kind regards,
> Zuheyr <CG1.step><pic2.png><pic1.png>_______________________________________________
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? 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine