# Basic 3D car physics, how to properly apply forces to wheels etc

## Recommended Posts

Hello,

I'm working on my first game at the moment, a 3D racing game for the web, using my proprietary engine.

Right now I'm just getting some basic car physics working. As performance is paramount, I'm representing the cars just as 3D rectangles. 4 particles and 5 constraints.

The particles represent the wheels. I'm playing around at the moment just with applying forces to the particles, steering etc.

However, I can't find a reference for 3D car physics. It would be very useful if I had some fundamentals on how to apply force to the wheels according to whether the car is FWD or RWD etc.

Should each wheel have it's own velocity, or should each wheel simply apply force to a single velocity on the car?

Right now to represent a RWD car I'm applying most of the force on the rear wheels, with just a small amount on the front wheels, with rotated velocity for steering. Presumably for a FWD drive car you simply only apply force on the front wheels.

On the RWD test I'm doing, the car's pivot point feels like it's too far back, at the very back of the car basically. In real life, it is the front of the car that swings around, with the pivot point being at least somewhat to the rear, but it feels slightly wrong.

What additional forces do I need to apply? I've heard people mention normal force, but it's not something I'm acquainted with in the fairly basic physics experiments I've done. When I've seen it mentioned, it seems almost like a centrifugal force.

And if you know of a solid reference for 3D car physics from scratch, that would be great.

Also, I'm not developing a simulation. I want the handling and feel to be very much more on the arcadey side, a la Ridge Racer, Daytona, Burnout etc.

But even being arcade style, obviously the cars need to feel like cars :)

Cheers,
RumbleSushi

##### Share on other sites
Have a look for the 'Pacejka formula'. This is a method for approximating the forces on each tyre for a given situation, and will also enable you to include effects like skidding and slipping.

##### Share on other sites
Thanks BMC, I'll look that up.

I forgot to say actually, once I'm happy with the basic mechanics and handling, the next step is to implement drift physics, as the game is arcade style touge game, so drifting is very important.

##### Share on other sites
Also, what is generally considered the best way to implement friction in a racing game?

I've heard several people say friction is tricky.

In the physics experiments I've done, including verlet based soft body dynamics, I always use the basic velocity *= friction, where friction is a damping value around 0.99 etc. I guess this is considered air drag.

Even in arcade racing games, do people generally use surface friction in addition to air drag?

Cheers.

## Create an account

Register a new account

• ### Forum Statistics

• Total Topics
627749
• Total Posts
2978913

• 10
• 10
• 21
• 14
• 14