SV: [ODE] Iterative solution

[Martin C. Martin]

> >can you (or someone) give a reason why position update is better? (i have
> >not done any experiments on this yet).

If you don't have position update, what happens when a stack of boxes
first penetrates the ground?  If it's a stack of n boxes, how many calls
to dWorldStep until all the bottom box is out of the ground and all boxes
don't intersect each other?  Assuming a large number of iterations that
is.  If it's 1, then somehow the bottom box is communicating with the top
box.  If the bottom box's velocity is constrained to be "up" so that it
moves out of the ground, and that forces the next box to have a velocity
of "up," and so on, then you've got the same situation I described.  In
this case, you need to know that the bottom box wants to move up before
you can know that the second lowest box should move up, etc.

- Martin