On Mon, May 15, 2023 at 9:30 AM Jed Brown <[email protected]> wrote:
> Matthew Knepley <[email protected]> writes: > > > On Fri, May 5, 2023 at 10:55 AM Vilmer Dahlberg via petsc-users < > > [email protected]> wrote: > > > >> Hi. > >> > >> > >> I'm trying to read a mesh of higher element order, in this example a > mesh > >> consisting of 10-node tetrahedral elements, from gmsh, into PETSC. But > It > >> looks like the mesh is not properly being loaded and converted into a > >> DMPlex. gmsh tells me it has generated a mesh with 7087 nodes, but when > I > >> view my dm object it tells me it has 1081 0-cells. This is the printout > I > >> get > >> > > > > Hi Vilmer, > > > > Plex makes a distinction between topological entities, like vertices, > edges > > and cells, and the function spaces used to represent fields, like > velocity > > or coordinates. When formats use "nodes", they mix the two concepts > > together. > > > > You see that if you add the number of vertices and edges, you get 7087, > > since for P2 there is a "node" on every edge. Is anything else wrong? > > Note that quadratic (and higher order) tets are broken with the Gmsh > reader. It's been on my todo list for a while. > > As an example, this works when using linear elements (the projection makes > them quadratic and visualization is correct), but is tangled when holes.msh > is quadratic. > > $ $PETSC_ARCH/tests/dm/impls/plex/tutorials/ex1 -dm_plex_filename > ~/meshes/holes.msh -dm_view cgns:s.cgns -dm_coord_petscspace_degree 2 > Projection to the continuous space is broken because we do not have the lexicographic order on simplicies done. Are you sure you are projecting into the broken space? Thanks, Matt -- What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead. -- Norbert Wiener https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
