[ODE] GTA3 and Physics

[Karlsson, Henrik]

It's very common that you use simple displacement in games when contacts
appear between objects.. and solve them one by one.. If you tweak it a
little you can make it look good..  cheap and simple :) Or you can always
solve displacement simultaneously. That might give you a better protection
against bodies penetrating each other when multiple contacts.

The big performance hit in game physics usually is the collision part
though. In our game right now 50% of the cpu is just collision detection..
(most graphics are done on the gpu). So keep your collision primitives as
simple as possible (use composites of spheres instead of boxes etc, works
good enough in most cases).

regards,

Henrik



-----Original Message-----
From: Filipe Dias [mailto:filipe.dias@mind.pt]
Sent: den 30 oktober 2002 20:49
To: ode@q12.org
Subject: RE: [ODE] GTA3 and Physics


What I remember from playing it is that when a seeding firetruck bumps 
into 2 cars at the same time the result is unexpected, the two cars stay 
still and the fire truck goes mad like if it had hit a wall. So this is 
very simmilar to "doesn't solve multiple simultaneous contacts"

Now judging by how good it looks, I am surprised how multiple contact 
situations happen that seldom!

Even so it is possible to push two stoped cars very slowly, so it is 
possible that multiple contacts can be solved if the speed is low...

Dispite all this I have mannaged to drive a firetruck inside a taxi!

Fil.


-----Original Message-----
From: "Phil Teschner" <philt@microsoft.com>
To: "Erwin de Vries" <erwin@vo.com>, <ode@q12.org>
Date: Wed, 30 Oct 2002 10:48:02 -0800
Subject: RE: [ODE] GTA3 and Physics

> I remember hearing that the physics engine in GTA3 was entirely written
> in house.  It is a pretty straight forward rigid body system that does
> not solve multiple simultaneous contacts (i.e. does not use an LPC
> solver).
> 
> Phil
> 
> -----Original Message-----
> From: Erwin de Vries [mailto:erwin@vo.com] 
> Sent: Wednesday, October 30, 2002 10:18 AM
> To: ode@q12.org
> Subject: Re: [ODE] GTA3 and Physics
> 
> > I'm guessing they are using a very customized physics model for
> gta3...
> They
> > might use havoc or similar package for most physics stuff.. but when
> it
> > comes to car physics in games it is much cheaper to have a customized
> system
> > compared to building up a vehicle correctly with different parts..
> 
> This is exactly what comes with Havok. A vehicle SDK. Now i have no
> idea
> how
> it works behind the scenes, and i've never used it, but my guess is
> that
> they are using many hacks to make it 'just work'.
> 
> Erwin
> 
> _______________________________________________
> ODE mailing list
> ODE@q12.org
> http://q12.org/mailman/listinfo/ode
> _______________________________________________
> ODE mailing list
> ODE@q12.org
> http://q12.org/mailman/listinfo/ode
> 


_______________________________________________
ODE mailing list
ODE@q12.org
http://q12.org/mailman/listinfo/ode