dolfin team mailing list archive

[angelo simone <a.simone@xxxxxxxxxx>]

Garth N. Wells wrote:
> angelo simone wrote:
> > Garth N. Wells wrote:
> > > angelo simone wrote:
> > > > Hi again,
> > > >
> > > > I read the manual... so, here is the patch. To convert a Gmsh mesh 
> > > > one must add an extra option to define the element type:
> > > >
> > > > dolfin-convert -i gmsh -o xml  -e <el_type> mesh.msh mesh.xml
> > > >
> > > > where <el_type> is either "tria" for triangles or "tet" for 
> > > > tetrahedra. Dolfin-convert will complain if one attempts to convert 
> > > > a Gmsh mesh without the -e option. The patch has been tested with 
> > > > triangular meshes but is should work fine with tetraheda as well.
> > >
> > > It should be possible to imply the element type from the gmsh file. 
> > > Can you post the gmsh output file which you're trying to convert?
> >
> > Sure. It represents a unit square which can has been meshed with 4 
> > crossed triangle selecting a large characteristic length factor, say 
> > 7, in the Gmsh input file after it.
> >
> > ---- Gmsh output
> >
> > $MeshFormat
> > 2 0 8
> > $EndMeshFormat
> > $Nodes
> > 5
> > 1 -0 -0 0
> > 2 1 0 0
> > 3 1 1 0
> > 4 0 1 0
> > 5 0.5000306693508283 0.5000716782088586 0
> > $EndNodes
> > $Elements
> > 8
> > 1 1 2 1 1 2 1
> > 2 1 2 2 2 1 4
> > 3 1 2 3 3 4 3
> > 4 1 2 4 4 3 2
>
> gmsh is outputting lines elements. You don't want these.
>
> > 5 2 2 6 6 3 2 5
> > 6 2 2 6 6 2 1 5
> > 7 2 2 6 6 4 3 5
> > 8 2 2 6 6 1 4 5
>
> These are the triangles that you want. If you create a "physical 
> surface", then gmsh will just output the triangles only.
>
> Garth
>
>
> > $EndElements
> >
> > ---- Gmsh input
> >
> > Point(1) = {-0,-0,0,0.1};
> > Point(2) = {1,0,0,0.1};
> > Point(3) = {1,1,0,0.1};
> > Point(4) = {0,1,0,0.1};
> > Line(1) = {2,1};
> > Line(2) = {1,4};
> > Line(3) = {4,3};
> > Line(4) = {3,2};
> > Line Loop(5) = {1,2,3,4};
> > Plane Surface(6) = {5};
> Physical Surface (7) = {6};
>
> Adding the above will do the trick.  You can also do it through the GUI.
>
> Garth


you are indeed right. I have just realized the mistake. thanks
angelo