This patent covers most workable methods of spring/damper
(or "penalty method") simulations of jointed, colliding
bodies. Prior to our work, the spring/damper approach
had largely been abandoned as unsuccessful. We made it work,
and Falling Bodies was the result. The patent contains a detailed
description of how it's done. We are now licensing this technology
to game developers.
In connection with the enforcement of our intellectual property rights, we have made various FOIA requests which may be of interest.