[Gmsh] GMSH renumbers elemntaty tags on reload

Christophe Geuzaine cgeuzaine at ulg.ac.be
Fri Jan 30 14:12:51 CET 2015


> On 30 Jan 2015, at 13:32, Zenker, Dr. Matthias <Matthias.Zenker at erbe-med.com> wrote:
> 
> Hi Mark,
> 
> to my experience, the "cut and merge" feature works only for simple cases. What you can do is to preprocess your geometry with Salomé. Load the STEP file, modify it if needed, make a partition (that makes the duplicates go away) and save that one as brep, then do the meshing with gmsh.
> Salomé has also a meshing module, but I find that gmsh is more powerful since it has more meshing algorithms implemented and gives better control over the result.
> 
> @Christophe: I don't know how the "partition" operation in Salomé works under the hood - would it be possible to implement it in gmsh?
> 

It would be very useful indeed to add this operation in Gmsh ; we interfaced the Salome class "Partition_Spliter" a while back, which was supposed to do this operation. But maybe there is something more to it? Any information in this regard would be useful; it's clearly a sore point in our brep/step import.


> HTH,
> 
> Matthias
> 
> 
>> -----Ursprüngliche Nachricht-----
>> Von: Christophe Geuzaine [mailto:cgeuzaine at ulg.ac.be]
>> Gesendet: Donnerstag, 29. Januar 2015 19:18
>> An: Mark Smith
>> Cc: gmsh at geuz.org
>> Betreff: Re: [Gmsh] GMSH renumbers elemntaty tags on reload
>> 
>> 
>>> On 29 Jan 2015, at 13:37, Mark Smith <piedycat at yahoo.com> wrote:
>>> 
>>> Hi Christophe,
>>> I agree that saving the cad geometry to a .geo file it is not the way
>>> to go but at least the surface numbers don't change on reload ;-) I have
>> some other cad geometry where I don't get this problem, which is why
>> perhaps you haven't seen it? have you any other suggestions I could try?
>> 
>> Maybe the best would be for you to send an (small) step file that exhibits the
>> problem? We could try to see where the non-deterministic numbering
>> comes from.
>> 
>>> Regards
>>> Mark
>>> 
>>> From: Christophe Geuzaine <cgeuzaine at ulg.ac.be>
>>> To: Mark Smith <piedycat at yahoo.com>
>>> Cc: "gmsh at geuz.org" <gmsh at geuz.org>
>>> Sent: Thursday, January 29, 2015 11:19 AM
>>> Subject: Re: [Gmsh] GMSH renumbers elemntaty tags on reload
>>> 
>>> 
>>>> On 29 Jan 2015, at 10:45, Mark Smith <piedycat at yahoo.com> wrote:
>>>> 
>>>> Hi Christophe,
>>>> Unfortunately it makes no difference ;-( I used cadexchanger from
>>>> http://www.cadexchanger.com/ to convert the step file into a .brep file
>> but this suffers with the same problem.
>>>> If is do file: save as and type say file2.geo and with the GEO
>>>> options box "save physical group lables"  ONLY ticked I get a file
>>>> with all the points, lines line loops etc. When I lad this the
>>>> element tag numbers stay fixed, ( it is relatively simple geometry
>>>> consisting of volumes bounded by plane surfaces) but I cannot get
>>>> the surfaces to be filled (rendered) but only crossed faces even
>>>> when I set
>>> 
>>> Mark - Do not save your .brep/.step as a .geo! Gmsh is designed to
>>> work directly with the native files - "translating" them to .geo is
>>> only there for very specific uses or debugging purposes: the .geo CAD
>>> kernel is far too rudimentary to handle all the complexities of
>>> .step/.brep
>>> 
>>> 
>>>> Geometry.SurfaceType = 2  this makes it difficult to pick surfaces to put
>> into surface physical groups infact changing Geometry.SurfaceType to 0 1 or 2
>> make no difference to the way the surfaces are displayed?
>>>> Strangely if I load in my cad geometry file Merge "file.STEP"; etc then the
>> surfaces displayed are as expected if one changes the setting of
>> Geometry.SurfaceType, any ideas?
>>>> 
>>>> Thanks in advance.
>>>> Best regards
>>>> Mark
>>>> 
>>>> 
>>>> From: Christophe Geuzaine <cgeuzaine at ulg.ac.be>
>>>> To: Mark Smith <piedycat at yahoo.com>
>>>> Cc: "gmsh at geuz.org" <gmsh at geuz.org>
>>>> Sent: Wednesday, January 28, 2015 7:11 PM
>>>> Subject: Re: [Gmsh] GMSH renumbers elemntaty tags on reload
>>>> 
>>>> 
>>>>> On 28 Jan 2015, at 15:36, Mark Smith <piedycat at yahoo.com> wrote:
>>>>> 
>>>>> 
>>>>> Gmsh version 2.8.5
>>>>> 
>>>>> Hi, I load a step file generated in solidworks saved in AP203 or
>>>>> AP214 format and load in into GMSH using a .geo file with the
>>>>> following lines
>>>>> 
>>>>> // in gmsh options-geometry make sure the "cut and merge faces" is
>>>>> checked // to remove duplicate entities on import of STEP file
>>>>> Merge "file.STEP"; Geometry.AutoCoherence = 1; Coherence;
>>>>> 
>>>>> in the options:geometry I get the model to display the surface
>>>>> labels with their elementary tags number, if I hit reload the tag
>> numbers change this make defining physical surfaces impossible since the
>> surfaces shown in the surface physical groups keep changing;-( I have not
>> had this behaviour before and at this moment it is a show stopper, is there a
>> way of preventing this behaviour?
>>>>> 
>>>> 
>>>> I don't see this behavior when I do the same thing over here (note that
>> "Geometry.AutoCoherence = 1; Coherence;" will have no effect on your
>> STEP data)... Does adding "Delete All;" before the "Merge" command help?
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>>> Thanks in advance
>>>>> Mark
>>>> 
>>>>> 
>>>>> 
>>>>> _______________________________________________
>>>>> 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
>>> 
>>> 
>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>>> 
>>> 
>>> --
>>> Prof. Christophe Geuzaine
>>> University of Liege, Electrical Engineering and Computer Science
>>> http://www.montefiore.ulg.ac.be/~geuzaine
>>> 
>>> 
>>> 
>>> 
>> 
>> --
>> Prof. Christophe Geuzaine
>> University of Liege, Electrical Engineering and Computer Science
>> http://www.montefiore.ulg.ac.be/~geuzaine
>> 
>> 
>> 
>> 
> 
> 
> 
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-- 
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science 
http://www.montefiore.ulg.ac.be/~geuzaine







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