[ODE] GTA3 and Physics

[Russ Smith]

> We implemented ODE in our real-time 3D authoring tool. I created a demo
> called 'Monster Mayhem' that demonstrates the vehicle simulation

nice!

>  - Stack overflow when there are too many collisions (because of a
> recursive function) If this occurs, the simulation is too slow anyway.

what recursive function do you mean? perhaps you mean a stack overflow in
the main ODE solver function - because too many collisions = too many
contacts = a big matrix that is slow to solve. if ODE moves to an
iterative LCP method then this problem might go away (lots of
experiments to do here).

>  - 'Bending wheels' when the wheel rotate extremely fast (this can be
> prevented by tweaking the simulation)

yes ... when i get all the other things on the TO-DO out of the way, i'd
like to try some solutions for this problem (i.e. 'glue the wheels back
on').

>  - Except for the hinge2 joint, the joints are not really usable, they are
> very un-rigid and they have a hard time keeping bodies together.

this is surprising ... but i can think of two ways this could happen. (1)
if the vehicle is rotating quickly through the air, errors in the
simulation may cause the wheels to pull apart. (2) if you are directly
setting the velocity of individual bodies to implement damping, the joints
will certainly pull apart, as the velocities at the joint points will no
longer match up. also on the TO-DO list is stable rotational damping.

>  - The way ODE works, makes heavy objects or objects that are under a lot
> of stress behave in a spongy way.

this should only be the case if that CFM number is high.

> (P.S. Russ, If you read this, can you put our page on your community
> list? http://www.quest3d.com/index.php3?id=116)

sure, this might take until after the weekend though.

russ.

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