Plot of quadrilateral mesh shows triangles

[ingvildsd]

Hi, this may be related to the bug discussed here:

Vtk_mesh for quadrilaterals plots as triangles

Plotting a quad mesh in pyvista produces a triangular mesh. A CG-1 space on a quad mesh properly shows a quad mesh, so it seems like this is in part hidden in dolfinx’s vtk_mesh implementation. Specifically, in the dispatched code for plotting meshes (and then the call to _cpp.io.extract_vtk_connectivity maybe?) # dolfinx v0.9.0 from mpi4py import MPI from dolfinx import mesh, fem, plot import pyvista domain = mesh.create_unit_square(MPI.COMM_WORLD, 10, 10, cell_type=mesh.CellType.quadrilater…

If so, a quick workaround seems to be going via a CG1 space, replacing

topology, cell_types, geometry = plot.vtk_mesh(domain, tdim)

with

CG1 = dolfinx.fem.functionspace(domain, ("CG", 1))
topology, cell_types, geometry = plot.vtk_mesh(CG1)