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Buggy physics

Started by YengaMatiC Oct 24, 2005 at 12:57 PM 3 replies 1.5k views

Original Post

Oct 24, 2005 at 12:57 PM

Hi, I'm about to start designing a buggy racing game with weapon systems. What i'm considering now is the feasibility of implementing realistic physics on it, without decreasing so much the playability of the game. I want a 3D game where you feel (and use) the physical differences between the available carts (suspensions, drifting, braking), but don't get annoyed with high reality physics effects like in racing games (Grand Turismo, F1, and all that). What models/algorithms do you recommend me? I thought in rigid bodies with verlet integration methods, but i'm a bit disconnected from physics. The other alternative is to use ODE or another physics engine, but maybe it's too much for what i am.

CodeMunkie

Oct 24, 2005 at 4:40 PM

Check out FragFist. Pretty similar concept to what you described. There is a good discussion about this project plus a demo on the OGRE forums. Maybe you can pick up some info there.

YengaMatiC

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YengaMatiC

Oct 28, 2005 at 11:37 AM

I have searched info about car physics (articles in gamasutra from jeff lander, physics series from GDmagazine, ...) and I've found that rigid bodies should do the job.
I've heard about raytrace vehicles, but I don't know much about them. It seems to be that you simulate suspensions tracing a ray to the floor and depending on the distance you apply a force to stabilize the vehicle. Although, there's a few issues with that method.

My main problem is how to model the wheels. I can have a rigid body for the chassis, but what about suspensions?
How do they do it in games like GTA3 (or any arcade with funny car physics)?

gazz

Oct 28, 2005 at 7:01 PM

GTA uses raytracing. I guess it's the fastest and most popular solution for vehicle physics. As long as the physics engine supports raycasting(i know that tokamak does) it's pretty easy to implement suspension. the hardest part is slip angle / slip ratio and tweaking of them. You can take a look at Novodex too. I don't know much about ODE, but when i tried it - it looked like it's more for scientific applications than games(problems with stability/speed in realtime) but that was more than a year ago.
PS - implementing your own physics is rewarding for learning of physics, but if you are familiar with forces and torques, reinventing the wheel is time consuming and unnecessary!

YengaMatiC

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YengaMatiC

Oct 29, 2005 at 4:25 AM

I think i'm gonna use a rigid body system with an RK4 integrator (it's not much different from an euler or midpoint solver, the same theory behind). I've read Gaffer article on spring physics and it seems they work good, but for some situations the system can explode.
I think raytrace wheels have springs as suspensions, isn't it? but how do you get the velocity of that wheel relative to the floor for damping?

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