[Gmsh] 360 degree rotation of structured hexahedral mesh using OpenCASCADE factory leads to "findRootSourceFaceForFace() failed"

[Christophe Geuzaine]

> On 20 Aug 2018, at 14:17, Sigve Karolius <sigve.karolius at ntnu.no> wrote:
> 
> Hello,
> 
> First of all I would like to thank you for making the excellent GMSH software publicly available.
> 
> Now on to my question. I am trying to rotate a surface around an axis four times; thus, generating a structured hex mesh of a volume in the shape of a "shell".
> 
> In the attached example you can try to generate the shape of a hollow pipe (simple example for illustration purposes) with and without  `SetFactory("OpenCASCADE");` by rotating a rectangle four times about an axis. By running the example (requires version 3.X) in the GUI you can see how the error `findRootSourceFaceForFace() failed` appears when the OpenCASCADE is used. The attached PNGs are screenshots of the respective result. 
> 
> My question is if there is simply something I have completely missed in the manual?

No, it's a limitation of the current implementation of extrusion combined with the OpenCASCADE kernel : when doing fully symmetric geometries we can't track the original surface - because it is replaced in the model. It's in our TODO list, but we don't know yet how to fix this...

Christophe




> 
> Regards,
> 
> Sigve Karolius
> 
> 
> 
> <no_opencascade.png><opencascade.png><untitled.geo>_______________________________________________
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— 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine

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