[Gmsh] GMSH renumbers elemntaty tags on reload

Fri Jan 30 13:32:21 CET 2015

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?

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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