[Gmsh] Some hints to solve self intersecting surface errors?

[Mario Ceresa]

Thanks Matthias,
I'll do as you say.

Best,

Mario

On 08/20/2013 11:57 AM, Zenker, Dr. Matthias wrote:
> Hi,
>
> the problem is indeed that the solids have touching surfaces. If the geometry is defined with gmsh, you can use the same surface as outer surface for more than one solid. This would avoid the problem, but AFAIK in CAD this is not possible.
> Maybe you could just define(uniquely)  the outer faces in your CAD (without the solids), merge them into a geo file and define the solids with gmsh.
> As I wrote, gmsh cannot (yet?) "heal" this kind of problems by identifying and merging the duplicate surfaces. If I have a problematic geometry, I save it as geo file and remove the duplicated surfaces by hand, waiting for a better solution...
>
> Matthias
>
>> -----Ursprüngliche Nachricht-----
>> Von: Mario Ceresa [mailto:mario.ceresa at alma3d.com]
>> Gesendet: Dienstag, 20. August 2013 11:22
>> An: Zenker, Dr. Matthias
>> Cc: gmsh at geuz.org
>> Betreff: Re: AW: [Gmsh] Some hints to solve self intersecting surface errors?
>>
>> Hi Matthias,
>> thanks for your mail. I tried to remove the smaller cilinder and indeed cut and
>> merge does modify the geo, albeit in a strange way (there are volumes made
>> of only one surface). It still segfault during 2d meshing.
>>
>> Meshing joint2.igs *without* cut-and-merge still complains about self-
>> intersecting faces.
>>
>> I attach the iges model and the geo file saved after the import and the
>> automatic cut and merge.
>>
>> I wonder if the problem is that i create three separate solids which have
>> touching surfaces. Maybe I'm not supposed to do so? If this is the case,
>> which is the right way?
>>
>> Thanks and regards,
>>
>> Mario
>>
>> On 08/19/2013 04:09 PM, Zenker, Dr. Matthias wrote:
>>> Hi,
>>>
>>> this is a known problem, and there exists no proper solution within gmsh
>> (yet?).
>>> To see the problematic faces, you can merge the intersect.pos file gmsh
>> generates. Then you can try to resolve the problematic faces directly in your
>> CAD or by saving your input file in geo format and modifying that one.
>>> IF your case is not much more complicated than your testcase, it might
>> suffice to resolve the partial overlap between the outer surfaces of the small
>> and the large cylinder. If you omit the small cylinder (volume 3 in gmsh) for
>> testing, does "cut and merge faces" work between the others?
>>> HTH,
>>>
>>> Matthias
>>>
>>>> -----Ursprüngliche Nachricht-----
>>>> Von: Mario Ceresa [mailto:mario.ceresa at alma3d.com]
>>>> Gesendet: Montag, 19. August 2013 10:14
>>>> An: gmsh at geuz.org
>>>> Betreff: [Gmsh] Some hints to solve self intersecting surface errors?
>>>>
>>>> Dear all,
>>>> My workflow is to use Sketchup to quickly create the geometry, export
>>>> it as iges and then mesh it with gmsh. Sometimes, usually when I have
>>>> many co- planar faces, I get the error:
>>>> "Self intersecting surface mesh, computing intersections"
>>>>
>>>> and meshing fails. I attach an example. I tried "Cut-and-merge-faces"
>>>> option but it segfaults during 2d meshing.
>>>>
>>>> Which is the proper way to solve this? Is there a way to "see" the
>>>> problematic faces so to know which parts of the geometry to change?
>>>>
>>>> Thanks and regards,
>>>>
>>>> Mario
>>>
>>>
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>
> _____________________________________________________________________
> ERBE Elektromedizin GmbH
> Firmensitz: 72072 Tuebingen
> Geschaeftsfuehrer: Christian O. Erbe, Reiner Thede
> Registergericht: Stuttgart HRB 380137
>