Ashton Peters wrote:
> Hi,
>
> I have an stl file generated in another program that I want to use as input,
> and create a 3D tetrahedral mesh with Gmsh. I can import the stl by opening a
> .geo file with the following contents into Gmsh:
>
> Merge "surf.stl";
> Surface Loop (1)= {1};
> Volume (1)= {1};
> Recombine Surface {1};
>
> ... here obviously my stl file is called "surf.stl".
>
> After importing the stl I can generate a 3D mesh easily.
>
> The problem is that I have no idea how to impose any kind of size control on
> the 3D elements Gmsh creates. All I want to do is control mesh size using a
> single number that represents an average element edge length (or similar)
> across the entire mesh. Characteristic lengths don't seem to work, as my stl
> import has no points associated with it that I can assign a characteristic
> length. I've tried Fields, but nothing I try seems to have any effect on the
> size of the final mesh - it always ends up with the same size elements!
>
> I'm sure Gmsh can do this (very simple) task, but I am getting lost amongst a
> lot of very flexible, complicated, and sparsely-documented controls, and I'm
> now stuck.
>
> Can someone please tell me what I need to do to impose a constant size
> control on an imported stl file when meshing with simple tetrahedral
> elements? Ideally I want Gmsh to re-mesh the surface with the new element
> size before meshing the internal volume.
>
> Thanks in advance for any help. I'm using Gmsh 2.2.0 on Windows, ideally in
> non-interactive mode.
Hi Ashton - The case of STL files is a bit special: since there is no
CAD, Gmsh infers the size of the elements inside from the size of the
elements on the boundary. To disable this, use
Mesh.CharacteristicLengthExtendFromBoundary = 0;
Then you can fix the size inside using the usual options, e.g.:
Mesh.CharacteristicLengthMax = the_max_elem_size_you_want;
>
> Ashton
>
--
Prof. Christophe Geuzaine
University of Liege, Electrical Engineering and Computer Science
http://www.montefiore.ulg.ac.be/~geuzaine
_______________________________________________
gmsh mailing list
[email protected]
http://www.geuz.org/mailman/listinfo/gmsh
