[Gmsh] stp import and periodic BC's

gdemesy at physics.utoronto.ca gdemesy at physics.utoronto.ca
Thu Jun 10 17:49:58 CEST 2010

Hi Gmsh users and developers,

I'd like to produce a x-,y-,z-periodic mesh of a CAD (stp) geometry. I
should mention that my stp shape is continuous across a period
(indeed, a CAD sphere inside a "periodic cube" is OK). There seem to
be an problem due to stp=>geo conversion necessary to perform
the extrusion hack.

I'm trying to understand why the rather unholy workaround crashes
(please see the png file in the attached archive):
A- import the "inner faces" (step generated via OCC), and the periodic box 1.
B- import the periodic box. This box is a stp generated via OCC, saved
as a box.geo where the extrusion is performed.

Well, something's wrong with that (probably a mismatch between edges):
"Error   : Something wrong in edge loop
Error   : Plane surface 10 (0.536503x+-0.843851y+-0.0089615z=-18.5513)
is not plane!
Error   : Control point 4 = (16.6654,40.5491,71.5), val=-7.36574"

Would you have any other idea ? Since the gmsh geo-export
does not deal with ruled surface, I cannot convert my inner
"missing face" to .geo. I guess this ought to be easier to do with the
future release...

I attached a zip with a sketch, the cad & geo files.
Thanks a lot for your time.


Guillaume Demésy

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