[ODE] GTA3 and Physics

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..

Fil.

-----Original Message-----
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

> Hi,
> 
> 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
> physics   
> 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
> run   
> 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
> simply   
> 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
> body   
> 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   
> testing:
> 
>  - 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
> are   
> 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
> hinge   
> 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
> CFM   
> and ERP values made some improvements but they did not solve the   
> problem.)
>  - The way ODE works, makes heavy objects or objects that are under a
> lot   
> of stress behave in a spongy way. This is not a real problem because
> you   
> 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
> if   
> 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,
> suggestions   
> 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
> already   
> 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
> alternative   
> to commercial physics engines although it is more limited of course.
> Hey,   
> its free and it works like a charm so why should you complain about it?
> 
> Have a look:
> http://www.quest3d.com
> 
> You can download the demo version of Quest3D and experiment with ODE   
> yourself.
> 
>  -Remko
> 
> (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:aanand@milestoneindia.com]
> Sent: Wednesday, October 30, 2002 10:05 AM
> To: ode@q12.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.
> 
> Thanks
> AN
> 	
> 
>  ---
> Outgoing mail is certified Virus Free.
> Checked by AVG anti-virus system (http://www.grisoft.com).
> Version: 6.0.401 / Virus Database: 226 - Release Date: 10/9/2002
>    
> 
> 
> 
> _______________________________________________
> ODE mailing list
> ODE@q12.org
> http://q12.org/mailman/listinfo/ode
> _______________________________________________
> ODE mailing list
> ODE@q12.org
> http://q12.org/mailman/listinfo/ode
> 