Msh to xml for quad elements

[dokken]

@bagla0

I am again wanting to assure that, using meshio, we can get workable quad mesh for FEniCS/Dolfin.

As I said in the previous post

@dokken

There is no proper support for quad elements in legacy Dolfin. See dolfinx

In DOLFNx, you can load these meshes with no problem.
I believe that you cannot use them with legacy DOLFIN (as I again said, the support isn’t there).

@bagla0

I am finding difficulty to use these data for the FEniCS input as it was done in xml file using method Mesh and MeshFunction.

There are many post on how to read XDMFFiles into DOLFIN:
For instance:

Transitioning from mesh.xml to mesh.xdmf, from dolfin-convert to meshio

This can be done using meshio and writing the explicit data to xdmf file. import meshio msh = meshio.read("test.msh") meshio.write("mesh.xdmf", meshio.Mesh(points=msh.points, cells={"tetra": msh.cells["tetra"]})) meshio.write("mf.xdmf", meshio.Mesh(points=msh.points, cells={"triangle": msh.cells["triangle"]}, cell_data={"triangle": {"name_to_read": msh.cell_data["triangle"]["gmsh:physical"]}})) from dolfin import * mesh = Mesh() with XDMFFile("mesh.xdmf") …

@dokken

from dolfin import * 
mesh = Mesh()
with XDMFFile("mesh.xdmf") as infile:
    infile.read(mesh)
mvc = MeshValueCollection("size_t", mesh, 2) 
with XDMFFile("mf.xdmf") as infile:
    infile.read(mvc, "name_to_read")
mf = cpp.mesh.MeshFunctionSizet(mesh, mvc)
File("dolfinmesh.pvd").write(mesh)
File("dolfincellfunc.pvd").write(mf)