[Gmsh] Combine single facets to surface group OR multiple STL files (closed surface) merged to get 3D mesh

Meiner Auchmeiner auchmeiner at googlemail.com
Fri Feb 26 20:36:16 CET 2010


thank you so much for your help - you made my day (and saved my
weekend ;)! It worked wonderfully.


2010/2/26 Christophe Geuzaine <cgeuzaine at ulg.ac.be>:
> On 26/02/10 10:15, Meiner Auchmeiner wrote:
>> Hello gmsh group,
>> first of all I would like to thank Mr. Geuzaine and Mr. Remacle, and
>> all the other contributors, for this great software, thank you very
>> much!
>> I hope that somebody here can give me a hint towards the solution of
>> my problem. I'm trying to import a STL geometry (with one closed
>> surface) into gmsh and mesh it as a volumetric body with 3D elements.
>> The resulting mesh should ideally also consist of multiple surface
>> definitions on that body, in order to apply boundary conditions in the
>> framework of the Finite Element Method (FEM).
>> Firstly, I was able to import the STL file
>> (rabbit_mod_opt_500faces.stl) into gmsh (rabbit_mod_opt_500faces.geo)
>> and did get a decent 3D mesh (see screen1.jpg). But unfortunately I
>> wasn't able to select single facets - or find any other ways - to
>> define physical surface groups on that body (see screen2.jpg).
>> In a next approach I split-up the initial shell surface in advance
>> (thanks to meshlab) into two parts (see
>> rabbit_mod_opt_500faces_subset1.stl and
>> rabbit_mod_opt_500faces_subset2.stl) and merged them into gmsh (see
>> rabbit_mod_opt_500faces_subsets.geo). Now I'm able to add physical
>> surface groups but unfortunately I wasn't able to get a correct 3d
>> mesh (see screen3.jpg). I also played around with the orientation of
>> the input faces of the two STL files but didn't succeed (but I'm not
>> sure if I did it right).
>> My questions are now:
>> * Is it possible to pick single facets to combine them to multiple
>> physical surface groups?
> Yes, but it's not interfaces yet... In a future release :-)
>> * Is it possible to get a 3d mesh out of multiple surface shells (STL
>> files) merged together? If it is, what intermediate step would be
>> necessary to do so?
> You need to remove the duplicate mesh vertices:
> Merge "rabbit_mod_opt_500faces_subset1.stl";
> Merge "rabbit_mod_opt_500faces_subset2.stl";
> Coherence Mesh;
> Surface Loop(1) = {1,2};
> Volume(1) = {1};
>> * I read in a previous mail about an experimental feature called
>> compound surfaces - is it possible that I could use this to solve my
>> problem?
> Compound surfaces will allow you to remesh (refine/derefine) the initial
> STL.
> Best,
> Christophe
>> I would greatly appreciate any assistance.
>> Thanks,
>> Uwe
>> P.S.: The geometry I used for testing purpose comes from:
>> http://thevirtualheart.org/anatomyindex.html
>> _______________________________________________
>> gmsh mailing list
>> gmsh at geuz.org
>> http://www.geuz.org/mailman/listinfo/gmsh
> --
> Prof. Christophe Geuzaine
> University of Liege, Electrical Engineering and Computer Science
> http://www.montefiore.ulg.ac.be/~geuzaine