[ODE] Car simulation (with no wheels) - clever ideas needed

[DjArcas]

> First of all, for 200 cars, not all of them will be on screen and not
> all of them will be in the foreground. Therefore you need some sort of
> level of detail, not only for the graphics but for the physics and
> collision as well. Far away cars can be modelled as a box, closer cars
> have more appropriate physics, and the player's car must have perfect
> physics at all times.

I guess a picture speaks a thousand words here:

http://www.sawkins.com/pg/new/MegaSprint_Screen.png

> Secondly, investigate ODE's spaces. You put the whole car in a space,
> then subdivide the car into smaller spaces. You don't need to test every
> object all the time, test to see if any two AABBs collide, and if so,
> work your way in to more and more detail.

Hmm, interesting. There's a way of using 'bubbles' of collision that might
well help.

> Thirdly, use StepFast1 as much as you can, and take advantage of its
> assumptions. It's not perfect, but it certainly is fast.

I've had nothing but problems with stepfast1 so far *grins*

> Other than that, James Golding's idea is very good. Karma is a bit more
> optimised than ODE, which is why it costs a lot more, but the principles
> are the same.

*nods*
I've used Karma fairly extensively, before we rebranded it RenderwarePhysics
(and made it better :) - it really is very similar.

> BTW, why is your car routine so slow? AI? Complex graphics?

Sheer weight of numbers *grins*

> James
>
>
>
> DjArcas wrote:
>
> > Even if they aren't touching, I can't see my modern PC controlling 200
cars!
> > I've said, I've done this before, and my PC will barely do 30-40 cars,
> > BEFORE collisions! This is why I want my cars to be no more troublesome
to
> > the collision and resolver than a box. Surely this is possible? :)
> >
> > Adam
> >
> > ----- Original Message -----
> > From: "Jon Watte" <hplus-ode at mindcontrol.org>
> > To: "DjArcas" <djarcas at hotmail.com>; "Nate W" <coding at natew.com>;
> > <ode at q12.org>
> > Sent: Friday, March 19, 2004 6:18 PM
> > Subject: RE: [ODE] Car simulation (with no wheels) - clever ideas needed
> >
> >
> >
> >>>But I'm pretty sure that trying to field, say, a full pack of nascar
> >
> > cars,
> >
> >>>each with more accurate chassis than a box, with hinge2s for the
wheels,
> >
> > is
> >
> >>>going to bring your PC to it's knees.
> >>
> >>Let's assume they're all not touching, so that they're all their own
> >
> > islands. Further, let's assume they're driving on some mesh that has no
> > body, so it's the fixed environment. Are you sure that a modern PC
wouldn't
> > be able to handle this? Make sure to turn on all optimizations before
> > profiling this. I don't know how many cars go in a full NASCAR field,
but I
> > know they USUALLY don't collide all that often compared to how often you
> > step/render.
> >
> >>How to detect pile-up and switch to box-only simulation (and when to
snap
> >
> > out of that) is probably a black art, and where you get to show your
skills,
> > but AFAIK, that's how you can make seemingly intractable simulation
problems
> > actually work in real time for a game.
> >
> >>Cheers,
> >>
> >>/ h+
> >>
> >>
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