[Gmsh] importing .step files with multiple parts whose surfacestouch

[Zenker, Dr. Matthias]

Hi Brent,

I have had (and posted) this problem, and still have it.
What has been done AFAIK is that a functionality which should in principle do what we need has been implemented in gmsh, developped by Mark van Doesburg. But it works only in some cases (e.g. plane surfaces). If you want to try it, check "Tools->Options->Geometry->Cut and merge faces (experimental)", reload your geometry and see what happens.
I had thought for a while that the geometry healing functionality of Netgen could solve the problem, but it does not, at least not in 3D.
I am actually working on a solution of the problem, but I don't know yet what it will be. I see two possibilities:

1. Switch to another preprocessor. I evaluate GiD at the moment, which is not free, but not so expensive either. As far as i have found out so far, it can collapse the surfaces. But I still have some technical problems, i.e. GiD crashes sometimes for complicated geometries. If this problem cannot be solved by the GiD people, I have to opt for solution 2.

2. Program something myself. I have actually started to write a mesh processor. The idea is to take the 2D mesh (e.g. generated by gmsh), identify touching surfaces, merge them, reload the cleaned up mesh in gmsh, re-define the volumes, and generate the 3D mesh. For the moment, my program just reads and orders the mesh. I will continue to work on it as long as the GiD problem is not solved.

That's the status from my point of view.

Matthias


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ERBE Elektromedizin GmbH
Dr.rer.nat. Matthias Zenker
Dipl. Phys.
Grundlagenentwicklung / Fundamental Development
Waldhoernlestrasse 17
72072 Tuebingen
Germany
Phone + 49 (0) 7071 755 - 226
Fax + 49 (0) 7071 755 - 5226
E-Mail: <mailto:Matthias.Zenker at erbe-med.com>
URL: http://www.ERBE-med.com
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-----Ursprüngliche Nachricht-----
Von: Vandevender, Brent A [mailto:Brent.Vandevender at pnl.gov] 
Gesendet: Donnerstag, 31. März 2011 02:57
An: gmsh at geuz.org
Betreff: [Gmsh] importing .step files with multiple parts whose surfacestouch

I have looked through the mailing list archives and found that a couple of years ago some people were actively developing the capability to "sew" together the common surfaces of parts that touch each other (i.e., have a common surface).  I have also seen more recently that those same people have declared that effort a failure.  I wonder what is the current status of this capability in gmsh in case I have missed something.

I am trying to import the attached .step file made by our MEs so that I can do finite-element electric field modeling.  In the attached model there are 2 pieces, one should be a conductor and the other a press-fit insulator.  GMSH makes a beautiful 2D surface mesh, but the common surface consists of two meshes.  I think what I really need is for there to be just one mesh at the interface for subsequent 3D meshing and solving with getDP.  I have tried some options, Geometry.OCCSewFaces = 1 and Geometry.OCCConnectFaces = 1, with no success.  OCCConnect Faces at least recognizes the common surfaces in my model, but rather than merge them into one, it removes them both.  I am sure this has come up for others on the list, and I wonder what solutions people have figured out, if any.


--
Brent A VanDevender, PhD
Pacific Northwest National Laboratory
Radiation Detection and Nuclear Sciences Group

email:brent.vandevender at pnl.gov
phone:509-371-7982