Mesh extrusion and simplex conversion

[CodeFloh]

I'm gonna create one issue even though these aspects could be treated separately. I'm interested in the following functionality:

• Extrude a two-dimensional FE mesh to a three-dimensional mesh with a specified number of layers and thickness.
• Convert non-simplex to simplex meshes.

These two operations do not necessarily need to be separate. The following specific conversions are useful:

• 2D quadrilateral mesh to 2D triangle mesh
• 3D hexahedron mesh to 3D tetrahedron mesh
• 2D triangle mesh to 3D tetrahedron mesh

All these operations need to conserve the boundary information. Extrusion operations should add an additional boundary.

Answers to the following questions could help:

• How would these operations be carried out in gustav?
• Where in gustav can the functions be found?
• Where in gustaf should this functionality be implemented?

[j042]

2D quadrilateral mesh to 2D triangle mesh -> Mesh.tri_mesh
3D hexahedron mesh to 3D tetrahedron mesh -> As discussed, this would be not exact transformation (should give warning!), but I like the idea of providing simple 1 hexa to 6 tetra. and once we have a fancier "tetrahedralizer", we can extend this.
2D triangle mesh to 3D tetrahedron mesh -> gustav.mesh_shapes.extrude_volume

• Where in gustaf should this functionality be implemented?

=>gustaf/create/faces.py & gustaf/create/volumes.py ?

[j042]

@LinusKnecht @CodeFloh check out tetgenpy. It should provide stable and fast solutions for generating tetrahedrons and covers all the use-case you've stated above. We can discuss implementation details if you are interested

[LinusKnecht]

It looks quite nice to me at a first view. The conversion to gustaf and vice versa seems to work as well.