Implement a velocity/acceleration based error metric

[nfrechette]

We currently use a position based error metric. This simulates the skinning process as described here.

However, this does not really account for the error perceived by the end user on screen. For example, under high velocity, a larger error can be tolerated because it isn't as visible on account of the fast movement. An error of 5cm might be very visible when the velocity is low, but entirely invisible if sufficiently high. In the same vein, a large positional error could be tolerated on limbs not in contact with the environment/other things as there is no frame of reference for the user to evaluate accuracy. An error of 5cm on a floating hand is hard to see, but easy to spot if reaching for a door knob.

The general idea is that the first derivative (velocity) of our data might provide more relevant information when it comes to measuring error accuracy. Similarly, perhaps using the second derivative (acceleration) can be of use as well.

David Goodhue has published a paper where he uses velocity to compress animation data however I believe part of that work has been patented. See here: https://dl.acm.org/doi/10.1145/3102163.3102236