Conforming simplex mesh export

[cburstedde]

On the branch feature-triangle, currently at bbdc4ce, there is code to generate a conforming triangle (2D) or tetrahedron (3D) mesh from an existing p4est. While the forest is non-conforming adaptive, the export connects simplices at their corners only. The corners are considered owned or shared nodes in the sense of p4est_lnodes.h, and the simplex export is in p4est_tnodes.h. There is still a lot of temporary/debugging code in that file, which is all subject to change.

This is a public alpha release, and the preprint will be coming out soon. Presently, we are looking for feedback on

• the design of the data structure p4est_tnodes and its usability,
• correctness of the data that we populate by p4est_tnodes_new_Q2_P1,
• correctness of the VTK output (please see example/mesh/tnodes2.c).

To put the whole meshing pipeline together including adaptation and data transfer between meshes before/after adaptation/partitioning, there is a bit more code to write, which we will discuss separately.

Any feedback will be greatly apprecitated!