[Gmsh] gmsh 4.5.6: Creating a mesh from .vtk files - Surface is not remeshing but only the Volume

[Christophe Geuzaine]

> On 23 Jun 2020, at 10:16, Lisa Pankewitz <lisa at simula.no> wrote:
> 
> Hi Christophe,
> 
>  Thanks for the clarification, I misunderstood.
> 
> Could you maybe point me to a tutorial or an example that elaborates a bit more on how I would now tag the surfaces manually based on the vtk providing the boundaries?
>  I assume you tagged the surfaces and volume afterwards in order to create the nice figure you sent?

No I just used the script and set nice colors. After looking at your file in more detail though, we could actually do without reclassifying the input mesh if

1. we improve the VTK reader to create one surface per file (instead of loading all the triangles in a single surface)
2. you fix File_2.vtk (which has triangles oriented inconsistently)

I just coded 1. and manually fixed 2. Here's the resulting script, nice and easy ;-)

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You'll need the latest development snaphot to test it.

Christophe

> 
> Thanks!
> 
> 
> Kind regards,
> 
> Lisa 
> 
> ----------------------------------------------------------------------------------------------------------------------
> Lisa Pankewitz
> PhD student
> Simula Research Laboratory
> Martin Linges vei 25
> 1364 Fornebu
> Office 329
> lisa at simula.no
> 
> 
> 
> On Tue, 23 Jun 2020 at 08:30, Christophe Geuzaine <cgeuzaine at uliege.be> wrote:
> 
> 
> > On 22 Jun 2020, at 19:14, Lisa Pankewitz <lisa at simula.no> wrote:
> > 
> > Dear Christophe,
> > 
> > thanks so much for your helpful and fast response. It is really appreciated!
> > 
> > Just to double check: Does that mean that the assignment of surface names with the syntax I used before does not work any longer in gmsh ?
> > 
> 
> It does of course. But when new surfaces are created (by ClassifySurfaces) you'll need to identify them as well.
> 
> > Thanks so much and have a great day :)
> > Kind regards,
> > 
> > Lisa 
> > 
> > ----------------------------------------------------------------------------------------------------------------------
> > Lisa Pankewitz
> > PhD student
> > Simula Research Laboratory
> > Martin Linges vei 25
> > 1364 Fornebu
> > Office 329
> > lisa at simula.no
> > 
> > 
> > 
> > On Mon, 22 Jun 2020 at 18:10, Christophe Geuzaine <cgeuzaine at uliege.be> wrote:
> > Hi Lisa,
> > 
> > Your script seems quite complicated. Here's a simple one that produces a decent mesh:
> > 
> > Merge "File_1.vtk";
> > Merge "File_2.vtk";
> > Merge "File_3.vtk";
> > Merge "File_4.vtk";
> > Merge "File_5.vtk";
> > Merge "File_6.vtk";
> > Merge "File_7.vtk";
> > 
> > Coherence Mesh; // remove duplicate mesh nodes
> > 
> > ClassifySurfaces{21 * Pi/180, 1, 0 /* or 1 */, 40 * Pi / 180};
> > CreateGeometry;
> > 
> > Mesh.CharacteristicLengthMax = 10;
> > Mesh.CharacteristicLengthMin = 0.1;
> > Mesh.CharacteristicLengthFromCurvature = 1;
> > Mesh.MinimumElementsPerTwoPi = 20;
> > 
> > s() = Surface{:};
> > Surface Loop(1) = s();
> > Volume(1) = 1;
> > 
> > We still need to add some tools to automate the identification of curves/surfaces created by ClassifySurfaces. For now you'll need to tag them manually (or use some geometrical tests, e.g. using the Gmsh API).
> > 
> > Christophe
> > 
> > <ok.png>
> > 
> > 
> > 
> >> On 22 Jun 2020, at 17:25, Lisa Pankewitz <lisa at simula.no> wrote:
> >> 
> >> To whom it may concern,
> >> 
> >> I am trying to remesh a geometry based on .vtk files.
> >> I merge 7 .vtk files. 4 vtk files are used to create a surface that consists of 4 compounds. All 7 surfaces together define the volume. I assign tags (names) to the physical surfaces, which I need in later steps. Unfortunately, I realized the surface does not remesh. I checked several tutorials and parameters but could not yet find a possibility to keep the tags and remesh the surface and the volume in the assigned characteristic length in gmsh version 4.
> >> I tried
> >> ''' 
> >> RefineMesh
> >> '''
> >> but this only splits the elements instead of performing an optimal refinement.
> >> 
> >> Do you by chance know what I could assign in order to remesh the surface AND the volume and not only the volume?
> >> 
> >> Thanks so much for your time and have a wonderful day!
> >> Kind regards,
> >> 
> >> Lisa 
> >> 
> >> ----------------------------------------------------------------------------------------------------------------------
> >> Lisa Pankewitz
> >> PhD student
> >> Simula Research Laboratory
> >> Martin Linges vei 25
> >> 1364 Fornebu
> >> Office 327
> >> lisa at simula.no
> >> 
> >> <File_4.vtk><File_3.vtk><File_2.vtk><complex.geo><File_1.vtk><File_5.vtk><File_6.vtk><File_7.vtk>_______________________________________________
> >> gmsh mailing list
> >> gmsh at onelab.info
> >> http://onelab.info/mailman/listinfo/gmsh
> > 
> > ? 
> > Prof. Christophe Geuzaine
> > University of Liege, Electrical Engineering and Computer Science 
> > http://www.montefiore.ulg.ac.be/~geuzaine
> > 
> > 
> > 
> > _______________________________________________
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> > gmsh at onelab.info
> > http://onelab.info/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