[ODE] solving penetrations "statically"

Erin Catto erincatto at sbcglobal.net
Wed Jun 7 17:47:43 MST 2006

Right, ODE uses a Baumgarte style position correction by feeding back the
position error into the velocity constraint. This works well for getting
closer to the right position by the end of the step. However, the Baumgarte
term affects the momentum and that can be undesirable. The propagated
velocity should not involve position feedback. Rather than solve two LCPs
(one in velocity and one in position), one can cheat and solve the two LCPs
simultaneously using the PGS algorithm. The first LCP is the one already
used by ODE (with position correction). The second LCP is the pure velocity
I'm sorry if this is confusing. I am assuming (possibly incorrectly) that
the OP understands the PGS algorithm. If not, I suggest reading Kenny
Erleben's thesis (http://www.diku.dk/~kenny) or checking out the articles on
my site (http://www.gphysics.com).

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