I'm trying to write code to transfer animations that were designed for one skeleton to look correct on another skeleton. The source animations consist only of rotations except for translations on the root (they're the mocap animations from the CMU motion capture database). Many 3D applications (eg Maya) have this facility built-in, but I'm trying to write a (very simple) version of it for my game.

I've done some work on bone mapping, and because the skeletons are hierarchically similar (bipeds), I can do 1:1 bone mapping for everything but the spine (can work on that later). The problem, however, is that the base skeleton/bind poses are different, and the bones are different scales (shorter/longer), so if I just copy the rotation straight over it looks very strange:

I've tried multiplying by the original bone's absolute rotation, then by the inverse of the target, and vice-versa... kind of a shot in the dark, and indeed it didn't work. (Tried relative transformations too)... I'm not sure where to go from here, so if anyone has any resources on stuff like this (papers, source code, etc), that would be really helpful.

Thanks!