[Gmsh] Creation of simple surface mesh

[Christophe Geuzaine]

> On 3 Jun 2019, at 16:04, Florian Lindner <mailinglists at xgm.de> wrote:
> 
> Hi Christophe,
> 
> thanks for your help! I have compiled gmsh from git to try it.
> 
> I am able to successfully remesh (double click on viewport -> change Global Mesh Size Factor), then click Mesh -> 2D to remesh.
> 
> Some questions:
> 
> * How can I change the meshing algorithm?

The same as for CAD surfaces: Tool->Options->Mesh->General and choose the 2D algo you want. You can also do all of this from the command line, e.g. 'gmsh file.msh -2 -clscale 0.1 -algo frontal', or in a script.

> 
> * Is there a way to achieve a smiliar semi-automatic meshing on the STL file of the bunny? Or is underlying parametrization you provided required?
> 

You need to create the parametrization. With the current development version you can do it this way:

- open the stl
- launch the "Reclassify 2D" tool (in the module tree, under Mesh)
- select all elements, check "Create parametrized discrete model" then "Reclassify"
- 'File->Save as' and choose a filename with an '.msh' extension

This procedure will change (will be made simpler! :-) in the final release.

Christophe


> Thanks a lot!
> Florian
> 
> Am 29.05.19 um 16:07 schrieb Christophe Geuzaine:
>> 
>> Hi Florian,
>> 
>> This is a nice test-case for our new remeshing pipeline. It's still quite experimental, but you can give it a try with the latest development snapshot: just open the attached .msh file, which contains a mesh of the bunny as well as an underlying parametrization. You can remesh this file simply by selecting the algorithm ("Frontal-Delaunay" in the attached picture) and the mesh size you want (e.g. by double-clicking in the window and changing the global mesh size factor).
>> 
>> Nothing about the new remeshing features is documented yet, but feel free to play around with it and report your findings ;-)
>> 
>> Christophe
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>>> On 29 May 2019, at 15:25, Florian Lindner <mailinglists at xgm.de> wrote:
>>> 
>>> Hello,
>>> 
>>> I have an existing surface geometry, which is the Stanford bunny [1] as PLY format.
>>> 
>>> My goal is too evaluate a mapping algorithm on a non-trivial geometry. The algorithm works only on point data, therefore I don't need an triangulation.
>>> 
>>> From the existing surface data I want to generate sampled points of various densities on the surface of the geometry and save these as a standard data format (e.g. VTK).
>>> 
>>> As I want to generate different mesh sizes, I need something like a background mesh size or a characteristic length which controls the sampling frequency. The exact placement of the points is not important, it should "make sense", i.e. be roughly equidistant or maybe influenced by the curvature.
>>> 
>>> So far I have only Merge "bun_zipper.ply"; in my .geo file. 
>>> 
>>> I think you can feel, that I am very uncertain how to progress and I would be very happy for guidance!
>>> 
>>> Thanks!
>>> Florian
>>> 
>>> 
>>> [1] http://graphics.stanford.edu/pub/3Dscanrep/bunny.tar.gz
>>> 
>>> _______________________________________________
>>> gmsh mailing list
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>>> 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