[ODE] Iterative solution

[Billy Zelsnack]

>Gary R. Van Sickle said:
>
>I don't see why you have to or even want to keep the island idea.  Well I
>suppose for collision detection it's probably still useful, but for doing
the
>solving, each constraint is treated as its own "island" by definition
(i.e.,
>you're dealing with it in isolation, without regarding any other
constraints).

Islands are still important because each island can converge in its own
number of steps. Sometimes an iterative solver can solve to an acceptable
error threshold in as little as a single iteration. The very next time step,
that same system could take many, many more iterations. There is no reason
to bog down all constraints with extra work, when only a few are typically
trouble makers.

-billy