Is it possible to obtain dense correspondence field? I am working on a computer vision algorithm and I have a very simple scene of a rotating sphere, rotating about the z axis. I would like to know 3d point by point correspondences for every frame. I have tried a couple of way to get this but not entirely satisfactory. One is I use the speed pass to obtain 2d flow vectors and then using multiple cameras to obtain 3d flow field which would give me 3d correspondences but i think it's not accurate enough. Is there a more exact way built into blender?
This answer may have missed the point, but maybe it will help clarify the question:
If you subtract the Object space coordinate of the shading point in the space of object A from the Object space coordinate of the shading point in the space of object B, then the colors on the surface-points of B will represent the World space 3D translation required to take them to the corresponding points on A.

This is OK for rigid objects.. if they're deforming, you could bake the space into an image texture, and look up in UV space instead.