Hexahedron Dominant Meshing with Hexahedron and Tetrahedron Elements only

In most cases the Hexahedron Dominant Meshing will include Hexahedron, Pentahedron, Pyramid and Tetrahedron elements.

I want to
generate the Hexahedron Dominant Meshing with Hexahedron Dominant and Tetrahedron only.
convert the Hexahedron Dominant Meshing into a new mesh with Hexahedron Dominant and Tetrahedron only.

I found an old thread [Gmsh] Regular mesh only composed by tetrahedra, it mentioned that:

  1. Export a GMSH mesh composed of hexaedra in VTK.
  2. Open it in ParaView and apply the filter Tetrahedralize to create a
    tetrahedral mesh.
  3. Click on Save Data to save it as VTU.

Is it possible to export the non-Hex elements only and use ParaView to convert them to tet elements?
Or is there other way to do this?

Since I did not see any reply for this item, I’ll take a quick stab at the issue, in case you want to write your own filter.

Assume that a Pentahedron can take two forms:

  1. One quadrilateral base, like a pyramid. For this case, split it into two tetrahedra by making a diagonal along the quadrilateral base. You can split it one of two ways. I would split it using the diagonal that makes the best tetrahedra quality. The same split is performed on Pyramid elements.
  2. Three quadrilateral sides, like a triangular prism. For this case, there are 6 choices. For one node, add lines to the two nodes it is not already connected to. This splits it into 2 tetrahedron. Pick the best node of the 6 in terms of shape quality.

For shape quality, I used Shewchuk’s scale invariant quality metric from the middle of Table 4.


For any reader who wants pictures of Pentahedron elements, see:

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