How to save a mesh in gmsh format

Question

I have a mesh created in this way

omega = BoxMesh(-6, -4, -4, 6, 4, 4, 10, 10, 10)

and saved is this way

File('temp.xml') << omega

¿how to convert the 'temp.xml' file to gmsh format?

Answer 1

You will need to write a converter by yourself. You can check dolfin/site-packages/dolfin_utils/meshconvert/meshconvert.py for the way a reverse conversion is done. You can also commit your work there. Another way is to stick to io module framework.

Answer 2

Support for gmsh output will not be supported in DOLFIN.

If you want mesh output against a community standard/specification, use XDMF.

Answer 3

Hi,
a simple solution would be to use Octave and the packages msh and fpl.
You can do as follow:
1) save the mesh in the .xml file as you are doing in Dolfin
2) load the mesh in Octave using msh
3) save it in a format compatible with gmsh using fpl
Quite long but you don't have to write code :-)

Comments

I am trying to implement what gedeone has mentioned above:
This is a function that receives a mesh, sends it to gmesh, remeshes it, gets it back and returns the refined mesh. When I run this script, there is an error regarding octave library refers to:

oct_msh = octave.mshm_dolfin_read('f1.xml.gz')

Note: I have installed octave, gmsh, etc. other octave commans work but this one.

Moreover, how does the rest of the code look like?

def gmsh_refine(mesh):

        dolfin.File('f1.xml.gz') << mesh 

        f2 = open('out.geo', 'wb')

        # writing geo file for gmesh
        f2.write('''
        Mesh.CharacteristicLengthFactor=0.1;
        Mesh.Algorithm3D = 4; //Frontal (4) Delaunay(1)
        Mesh.RemeshAlgorithm=1;
        Merge "f2.stl";

        Compound Surface(200)={1};

        Surface Loop(300)={200};
        Volume(301)={300};

        Physical Surface (501)={200};
        Physical Volume(502)={301};
        ''')

        #reading in octave
        oct_msh = octave.mshm_dolfin_read('f1.xml.gz')

        #writing for gmsh
        octave.msh3m_gmsh_write('f2.stl', oct_msh)

        #remeshing
        os.system('gmsh f2.geo -3')

        #converting to xml
        os.system('dolfin-convert f2.msh f3.xml')

      #reading for dolfin
    return dolfin.Mesh('f3.xml')