Volume Mesher

[bbarroqueiro]

Hi Michael

Its a small code that generates volume mesh from a surface mesh...

This was a issue i had and looking ate forums it quite frequent....

This code needs:
pip install gmsh-sdk
or since this sdk is so small it can included inside module!

Let me know what you think...

I hope his helps...

regards

[mikedh]

Nice, that looks like it could be very useful! Thanks for the PR! A few suggestions:

• I'd rename the submodule from trimesh.mesh3D to trimesh.volumetric or trimesh.fea, or something else
• trimesh.mesh3D.mesh3D -> trimesh.fea.to_bdf
• One goal of trimesh is to keep the mandatory dependencies to a minimum, so I'd like gmsh to be a "soft" dependency, i.e:

try:
    import gmsh
except ImportError:
    pass

• rather than using id_name_in and id_name_out I'd prefer to use tempfile.NamedTemporaryFile for both input and output. An example of doing this is here
• I'd rather the function returns the data from the bdf, and then the user can decide whether they want to write it to a file or not.

[bbarroqueiro]

Hi,
I tried to follow your suggestions...
But, in the last comment i think you should keep it as is... But i leave the decision to you... I don't mind at all...

Just remember that a 200K elements surface mesh can easily generate a few millions elements of volumetric mesh (it an be memory pit even in Fortran codes and python can be memory hungry). I would leave it to file.

If you return it and save it memory to do what? It should be export to be viewed, analysed and maybe optimized in order codes, right?

[mikedh]

No worries, yeah I totally get not wanting to load a 20gb tet mesh into memory. Maybe a compromise would be:

generate(file_name=None, ... )
"""
Parameters
---------------------
file_name : None or str
  If specified, will save the output to a file at the specified location 
  If None, the data will be returned as bytes
"""

[bbarroqueiro]

Hi, something like this code could be added:

if id_name_out != None:
    gmsh.write(id_name_out)
else:
    #Exports to disk for gmsh to read
    with tempfile.NamedTemporaryFile(suffix='.bdf') as id_out:
        pass
    gmsh.write(id_out.name)
    file = open(id_out.name, 'r') 
    return file.read() 

but it will be ascii since it is a input file for nastran or gmsh... I do not know how to work around this...

[mikedh]

Cool looks good! I'll try to merge this later this week, I want to play with it a bit more.

[bbarroqueiro]

I am been digging a little more in gmsh api. It should be possible to save the mesh in binary format using *.msh file extension. But it not working maybe i have an old SDK... i do not know...

For binary form it should be just

gmsh.option.setNumber("Mesh.Binary",1)

but doesn't work...

The Enhancement #206 is coved by this one and many other formats...
The gmsh script generates the 3D mesh based on the 2D mesh and exports everthing... So, if the 3D mesh is skiped the msh file will contain just the surface mesh...