http://graphics.ethz.ch/~mattmuel/publi ... sedDyn.pdfJakobsen built his Fysix engine on a position based approach. His central idea was to use a Verlet integrator and manipulate positions directly. Because velocities are implicitly stored by current and the previous positions, the velocities are implicitly updated by the position manipulation. While he focused mainly on distance constraints, he only gave vague hints on how more general constraints could be handled.
In this paper we present a fully general approach which handles general constraints. We also focus on the important issue of conservation of linear and angular momenta by position projection. We work with explicit velocities instead of storing previous positions which makes damping and friction simulation much easier.
According to that paper, position-based dynamics helps the two-way interaction between rigidbodies and cloth (for example).
This is something which has already been discussed on this forum before:
http://www.continuousphysics.com/Bullet ... .php?t=404
An older demo by Meqon (acquired by Ageia) showing cloth-rigidbody interaction:
http://www.continuousphysics.com/ftp/pu ... 202005.zip