Tangent and bitangent vectors for meshes in VTK
In addition to normals, we need to compute tangent and bitangent vectors for meshes for normal mapping. I think we can get away with just the tangent (since the bitangent is orthogonal to the tangent and the normal).
You can request this in Assimp. I wasn't able to find a filter for VTK, but I think it's supposed to be aligned with UV coordinates.