[Gmsh] Avoiding duplicate surfaces with OpenCASCADE kernel

Christophe Geuzaine cgeuzaine at uliege.be
Mon Mar 4 19:34:47 CET 2019

Hi Daniel,

It's one of the mysteries that we still haven't completely figured out with OpenCASCADE. I believe the issue is linked to our use of BRepBuilderAPI_Sewing to create shells ("surface loops"); but up to now we couldn't figure out how to create shells from surfaces without this, which indeed (sometimes) creates new surfaces...

Any insights from OpenCASCADE folks would be most welcome!


> On 4 Mar 2019, at 17:09, Ingraham, Daniel J. (GRC-LTV0) <daniel.j.ingraham at nasa.gov> wrote:
> Hi Gmsh users,
> I'm trying to mesh a geometry that has some rotational symmetry. In the
> past, I've used the Rotate command to help with this, with good results.
> With the built-in geometry kernel, everything works fine. With the
> OpenCASCADE kernel, however, Gmsh appears to duplicate surfaces when I
> define a new elementary volume after rotating the surfaces.
> I've read on this mailing list that OpenCASCADE will duplicate surfaces
> when they aren't oriented properly, and that this can be disabled if
> `Geometry.OCCAutoFix` is set to `0`. I've tried that, but the duplicate
> surfaces are still created.
> With the built-in kernel, the orientation of a surface can be reversed
> by negating its ID number in the `Surface Loop` call, but that doesn't
> appear to be the case when using the OpenCASCADE kernel.
> I've attached two example geo scripts that demonstrate the problem.
> `builtin.geo` uses the built-in kernel, and `opencascade.geo` uses
> Any ideas?
> Thanks!
> Daniel
> <builtin.geo><opencascade.geo>_______________________________________________
> gmsh mailing list
> gmsh at onelab.info
> http://onelab.info/mailman/listinfo/gmsh

Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 

More information about the gmsh mailing list