[ODE] multiple collision and "shivering"

[Russ Smith]

> > ...certainly the system will look much more stable but I don't
> > think that "shivering" will disappear.

actually, a box-plane collision can generate 3 contacts, and a 
box resting on a plane with 3 contacts is quite stable. so i'm
hopeful that box-box will be very stable.

> Partitioning the graph is a good idea, something that Havok said they
> do, and looks like something Russ mentioned as a 0.04 goal.

in fact ODE already does graph partitioning, so separate body-joint
systems ("islands") are simulated separately. but not simulating
unmoving islands at all is a "must have" feature for large VR
environments.

in the short term there'll be a feature to "turn off" bodies manually.
doing this automatically will come later. but note that it is a non-
trivial problem to determine when an island is statically stable,
especially when forces are being applied that balance gravitational
and frictional forces. some thinking will be needed here.

ress.

--
Russell Smith
http://www.q12.org