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

mesh
104

Yes, the tetra_data is a simple list of shape (numcells,). To illustrate this, you could use this example:

import numpy as np
import pygmsh
import meshio
def create_mesh_gmsh():
    geom = pygmsh.built_in.Geometry()
    rect = geom.add_rectangle(0.0, 2.0, 0.0, 1.0, 0.0, lcar=0.2)
    geom.add_physical([rect.line_loop.lines[0], rect.line_loop.lines[2]], 1)
    geom.add_physical([rect.line_loop.lines[1]], 2)
    geom.add_physical([rect.line_loop.lines[3]], 3)
    geom.add_physical([rect.surface], 4)

    # Generate mesh
    mesh = pygmsh.generate_mesh(geom, dim=2, prune_z_0=True)
    cells = np.vstack(np.array([cells.data for cells in mesh.cells
                                if cells.type == "triangle"]))
    triangle_mesh = meshio.Mesh(points=mesh.points,
                                cells=[("triangle", cells)])

    facet_cells = np.vstack(np.array([cells.data for cells in mesh.cells
                                      if cells.type == "line"]))
    facet_data = mesh.cell_data_dict["gmsh:physical"]["line"]

    facet_mesh = meshio.Mesh(points=mesh.points,
                             cells=[("line", facet_cells)],
                             cell_data={"name_to_read": [facet_data]})

    # Write mesh
    meshio.xdmf.write("mesh.xdmf", triangle_mesh)
    meshio.xdmf.write("facet_mesh.xdmf", facet_mesh)

Here mesh.cells contains 5 CellBlock, four of them with facet data.

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