UDK Motorsport: Pacejka's tyre model (the theory)

I've covered at length how to move the car. I needed to get a car with proper behaviour regarding acceleration in order to study the next topic in appropriate conditions.

That topic is tyre adhesion model. As the tyres are the only points of contact the car has with the road, they account for much of the vehicle's behaviour and that is why, from a design perspective, they're the most important aspect of car physics to understand. Unfortunately, it happens to be one of the most complex ones.

UDK Motorsport: Torque curves and engine sound

I have my gear plot. I need to find some way to combine that with the engine's torque curve in order to get the kind of curve Unreal requires. The obvious solution is to use the output of the gear plot as the input of the torque curve.

This is a basic mathematical tool called function composition. The problem is that while the gear plot is a set of linear functions, the torque curve isn't a function at all. So we need to find a function that has roughly the shape of the torque curve we are interested in.

UDK Motorsport: More about gear plots

I stopped my experiment about manual gear boxes when I got my proof of concept working. But the curves I used were a bit poo. I want to see how to create the sound of the engine according to its RPM, but I can't do it if I don't have proper torque curves. But how can I make those curves, based on an existing engine? (Warning: lots of maths involved here)

UDK Motorsport: Gears of Car

In the previous post I talked about torque curves, and Unreal's way of approximating them. My objective now is to create a manual gear box. As usual I'll first take a look at how things work in real life, then I'll see how to circumvent Unreal's annoying methods.

UDK Motorsport: acceleration and braking

The first thing we want to achieve with a car is make it go forward, and eventually make it stop. So let's have a look at how it (roughly) works in real life.

Basically, the engine spins at a certain speed, which makes the wheels (through the drive shaft) spin at the same speed (let's forget about the gear box for a moment). As the wheels spin, they make the car go forward (assuming there's enough grip to the road). Simple, isn't it? (yeah, I simplified a lot)

We're going to have a look at how acceleration works in Unreal, but first, let's talk about torque as I'll be using that term a lot.

Vehicle handling design: UDK Motorsport

Last month I looked into how vehicles work in Unreal. While in its default implementation the system is obviously not meant to create super realistic simulations, it's still quite complex and requires a bit of physics knowledge to get the big picture.

I'm going to try and see how far I can go with car physics simulation in Unreal. It will also allow me to give a shot at general vehicle handling design (which is a full-time job!). I will call this project UDK Motorsport.

As the topic is vast, I'll be making several posts on specific topics as I progress in my experiments. UDK will be the platform on which I will make my tests, but most of the theoretical bits should give readers insight on car simulation regardless of the engine used.

That said, chances are I'm going to talk about physics without really spending much time explaining everything in detail. If you intend to follow this series of blog posts, I hope you still remember your high school physics lessons (or your mechanic lessons if you've ever had some).