Bullet for car simulations.

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Wei Jin
Posts: 1
Joined: Sun Jul 03, 2016 10:03 am

Bullet for car simulations.

Post by Wei Jin »

I am currently using bullet to create a driving simulation that tries mimic the feel of real vehicles. I am currently modifying btRaycastVehicle, and has managed to model most mechanics. However, one thing that btRaycastVehicle does not seem to have properly is body roll physics, since it only casts ray downwards, the body roll is not realistic, since the suspension's degrees of freedom is limited.

I have seen multiple racing sims that have proper wheel suspension and wheels during cornering (e.g forza, project cars), which leads me to believe they are using constraint based systems. But at high speeds, the constraint based vehicle became increasingly unstable, and rigid body wheels cannot accurately depict the various forces affecting a tire.

My question is how do most commercial racing sims do their physics? If anyone can provide me papers or links that show techniques that i could employ that would be amazing.
benelot
Posts: 350
Joined: Sat Jul 04, 2015 10:33 am
Location: Bern, Switzerland
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Re: Bullet for car simulations.

Post by benelot »

The raycast vehicle is a simple approximation of a real vehicle, and you are right that it can not simulate the actual physical movements. That you need to correctly simulate a vehicle is definitely softbodies, especially the wheels. Look at the example browser softbody demos and checkout the one with the Bunny put on a car with 4 wheels. The wheels are totally overkill, but have an interesting softness, which might be more realistic than the rigidbody wheels.

If you combine it with car physics from something like those links, it might get you nearer to what you want to achieve.

https://nccastaff.bournemouth.ac.uk/jma ... Thesis.pdf

http://www.asawicki.info/Mirror/Car%20P ... Games.html

I am just googling and looking at the results. Maybe they help.

Btw, GTA uses Bullet and their cars look nice as well, so it is possible to simulate cars in Bullet. However, it might be very hard to get to such a level as for AAA games, there is usually a large team of experienced game programmers working several months to years, meaning that it is very unlikely to achieve the same as a single person.
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