I use mesh tension for shading purposes mostly (driving displacement maps, bloodflow, specular glossiness etc.).
For the specular anisotropy of my skin shader, I can get the amount of anisotropy from the stretch of the mesh (tensionMap.outRgbaPP) but I need a second value, which is the direction of the anisotropy. This is where a single rotation value in UV space would be perfect. This is what VRay and Arnold expects.
From the Arnold docs:
"The rotation value changes the orientation of the anisotropic reflectance in UV space. At 0.0, there is no rotation, while at 1.0 the effect is rotated by 180 degrees."
I have no idea how to make this conversion from vector to rotation in UV space mathematically, but that's where I hope you can help? :)
So if this is at all possible, perhaps outDirectionUvPP could be added in addition to outDirectionPP?