blendshapes tangent space vs object space?

[mostly_human]

I have read through the documentation but still dont understand the difference between tangent and object space and when to use one over the other.  

[jmreinhart · Accepted solution]

Object space:

The sculpt can be "re-angled" by the orientation of the object that it was paired with.

Tangent Space:

The direction the blendShape target gets applied in depends on the shape of the mesh. It kind of gets re-oriented to be "tangent" to the surface. 

Both of them have really niche uses, and in 3+ years of professional rigging I have never used either of them, the normal blendShape mode is just fine. The tangent-space does have the advantage of being able to apply corrections after a spacial deformer like a lattice or wire, since it would come at the end of the deformation order, but that is rarely needed.

Hope that helped