DMPlex support for quadratic (or higher) geometry
We discussed this a bit last summer, but we need a supported workflow for importing meshes with at least quadratic geometry. Quadratic geometry is supported by (at least) Exodus, MED, and CGNS. All three of these represent quadratic geometry by defining extra "nodes" for edge, face, and cell centroids. It is currently difficult to add this information to DMPlex.
I believe Matt still prefers MED because of the way it manages boundary conditions. Finding documentation for MED has been difficult for me because much of it is written in French. I don't have a strong preference here, though some meshes we need to work with come from Cubit, so we need some path from there. MED and CGNS are supported by Gmsh. We can add quadratic support to meshio (currently drops boundaries too) if needed. MED is a slightly shallower stack (HDF5-MED, versus HDF5-NetCDF-PnetCDF-Exodus).