[ODE] Pushing through collisions

[Russ Smith]

> Great! The only bit of data needed to complete the answer is: what is 
> the proportional constant used with the penetration depth to get the 
> moving-outward velocity?

the relevant lines of code are in joints.cpp:1258:

	dReal k = info->fps * erp;
	info->c[0] = k*j->contact.geom.depth;

fps is frames per second, i.e. 1/stepsize. what this says is "set the
velocity so that a fraction ERP of the penetration depth will be covered
in one time step".

> I'm assuming mass is also multiplied into the impulse to make it so
> that the velocity is the same no matter what the mass.

correct.

russ.

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