Forgot to assign to depsgraph project

About face center tangent, you don't have to average it, just pick the first met tangent for a vertex (first time it is found in a face loop) and ignore it next time it is met.
Not sure it can works this way through C / blender mesh things, but works great in python.

Hey! Some idea for your mush after giving it a try (blender python and houdini vex) and talking with Matt:
Basically, things should go this way:

• laplacian smooth rest mesh (here you can find basis formula, last of page 2 : http://www.ann.jussieu.fr/frey/papers/meshing/Bray%20N.,%20Notes%20on%20mesh%20smoothing.pdf)
• compute tangent space (TBN per point can be obtained with UVs, but can be compute using face center too (see bmesh calc_tangent implementation)
• store deltas per point in tangent space (btw smoothed mesh and rest mesh)