The system we used was based on a set of major nodes, feet, hands, pelvis, neck and head where anything in between is largely irrelevant. The system would play an animation file on these major nodes in an FK kind of fashion and while doing that would generate ik chains to drive the inbetween bits. on top of that it'd use…
Aha ! My specialist subject..... Retargetting can be done in realtime but its difficult and expensive as involves a lot more than just rotating stuff. Basically you need ik and you need target positions for any node that's important eg. feet. its not too bad if skeletons share the same hierarchy but is a minefield if…