[ODE] GTA3 and Physics
filipe.dias at mind.pt
Sat Nov 2 08:51:01 2002
I liked it much! the only criticism I have is that I find the car to
stable... What are you doing to make the car always stand up? My guess
is you have a "weight" under the wheels of the car..
Oh, and it is nearly impossible to make the loop..
From: "Remko Jacobs (act-3d.com)" <Remko@act-3d.com>
To: "ODE@q12.org" <ODE@q12.org>
Date: Fri, 1 Nov 2002 14:13:00 +0100
Subject: RE: [ODE] GTA3 and Physics
> We implemented ODE in our real-time 3D authoring tool. I created a demo
> called 'Monster Mayhem' that demonstrates the vehicle simulation
> capabilities of ODE. You get to drive around in stunt level with ramps,
> loopings and jumps. There are power-ups spread trough the level that
> change the car into a monster truck, reduce gravity, speed up time, or
> give the car a turbo engine. The results are just as good as the
> in GTA3. The capabilities of ODE really amazed me. To be honest, the
> results are better than I expected.
> To get everything working, we added several extensions to ODE. We made
> the collision routine work with our binary partitioning tree and we
> implemented better polygon collision. We also build in a feature so you
> can pin the simulation down to a certain frequency. This is VERY
> important because this ensures your perfectly tweaked simulation will
> the same way on any system. The source is available in our SDK. The SDK
> is downloadable in our support section.
> Another important feature we added is angular velocity damping. We
> reduce the angular velocity each step so rotating objects can come to a
> halt (simulated rotational friction). This feature is very important to
> get stable vehicles. By applying an angular velocity damping to the
> of the car, you prevent it from tipping over too quickly (keeping the
> simulation fun).
> These are the bottlenecks of ODE I found during a month of full time
> - Lack of certain collision shapes (cylinder, cone, pyramid)
> - Stack overflow when there are too many collisions (because of a
> recursive function) If this occurs, the simulation is too slow anyway.
> - Box stacking problem (a lot of info about this in the mailing list)
> - 'Bending wheels' when the wheel rotate extremely fast (this can be
> prevented by tweaking the simulation)
> - Except for the hinge2 joint, the joints are not really usable, they
> very un-rigid and they have a hard time keeping bodies together. The
> joints can only keep bodies together if the bodies are not too
> heavy.(Maybe we did something wrong here but I can't get a regular
> to behave as you would expect. At first, I planned a bridge in the demo
> but the hinge could not keep the bridge into its place. Tweaking the
> and ERP values made some improvements but they did not solve the
> - The way ODE works, makes heavy objects or objects that are under a
> of stress behave in a spongy way. This is not a real problem because
> can solve it by tweaking the simulation and it is the reason why ODE is
> so very stable. You can see this effect at the beginning of the demo
> where you see the balls squash into each other because the ball at the
> bottom is under so much stress. In some cases, this is actually a nice
> side effect.
> - It is impossible to prevent bodies from rotating. This is important
> you want to make a 1st person camera using ODE. Now, the character will
> always roll down a shallow slope. Maybe this is solvable now,
> are welcome.
> In the end, I must say ODE does a great job. The lack of certain
> collision shapes can be solved by coding them yourself and there
> is a cylinder shape in development. The box-stacking problem is not an
> ODE problem but just a problem in the collision detection routine. This
> problem can be solved with not to much effort it is just a matter of
> waiting until someone finds some time to fix it. I do not have a clue
> about the hinges but there is a lot you can do without using hinges :)
> ODE is very forgiving when it comes to errors. I can throw in random
> objects and ODE solves the physics perfectly. ODE is a great
> to commercial physics engines although it is more limited of course.
> its free and it works like a charm so why should you complain about it?
> Have a look:
> You can download the demo version of Quest3D and experiment with ODE
> (P.S. Russ, If you read this, can you put our page on your community
> list? http://www.quest3d.com/index.php3?id=116)
> -----Original Message-----
> From: Aanand Narayanan.P.P [mailto:email@example.com]
> Sent: Wednesday, October 30, 2002 10:05 AM
> To: firstname.lastname@example.org; Remko Jacobs (act-3d.com)
> Subject: [ODE] GTA3 and Physics
> Does anybody know which method (direct LCP, iterative LCP, penalty etc)
> was used in the (vehicle) physics for GTA3?
> Is it possible to achieve the same level of stability with ODE? I would
> like to hear from other people who have used ODE for full fledged
> physics simulations.
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