[ODE] iterative solver: testing needed

[Adam D. Moss]

gl <gl@ntlworld.com> wrote:
> Small problem compiling the test on MS VC:
> 
> ode/test/test_crash.cpp(205) : error C2086: 'i' : redefinition
> 
> simply remove "int i" at line 172.

I can't seem to make test_crash.exe display anything except
the ground-plane and the ball-in-the-sky -- though it's
simulating something because it gets slower when I add more
cars or wall blocks!

Additionally, dWorldStepFast() does funny things to my simulation's
friction, as if mu were being scaled differently (or is now timestep-
dependant?), because objects are continuing to slide around for somewhat
longer than they used to (possibly related to David's problem
-- don't know), even factoring in the fact that I had to disable
the auto-disabling of near-stationary bodies in my simulation
because dWorldStepFast() erronously continues to apply gravity
to disabled bodies.

Speedwise it lives up to its promises -- from some perfunctory
benchmarking it's never appreciably slower than dWorldStep() in
the easy cases, and does indeed scale much better performance-wise
in the many-contact-joints cases (I haven't tested for non-contact
joints).

In terms of memory usage I haven't benchmarked it at all, though
importantly it survives all the stress cases in which dWorldStep()
segfaults (presumably from extreme stack usage).

Stability-wise I find it better than anticipated; I was expecting
that inaccuracies in constraint satisfaction with too-few iterations
would lead to objects gradually sinking through each other (or,
the ultimate horror, 'exploding') but even when reduced to a
single iteration the worst that my 'enormous pile of objects'
does is slowly ripple gelatinously.

--Adam
-- 
Adam D. Moss   . ,,^^   adam@gimp.org   http://www.foxbox.org/   co:3
... but his bosses didn't like him so they shot him into space.