Basically, we were developing a math model for
tuning the cars. The hardest thing is, you can’t find, for example, spring rate
data for all 300 cars. You’re lucky if you can get it for 20% of them, from the
manufacturers and from research. Sometimes you can get that kind of data
on fan Web sites, which can be freaky that way. Sometimes we contacted
the spring manufacturers, not the car manufacturers. The manufacturers we
contacted were based on the continuum of all of the cars, so we could get
a really even spread of data on low-end cars to high-end cars to race cars,
finding out about progressive springs versus linear springs, and so on.
Then we looked at ride height, the weight of the car, and what we call the
“goodness rating,” from reading reviews and learning a lot about each car.
We ranked the cars based on their “goodness,” and arranged those values
into buckets. For example, we might put a Ford Focus SVT a little lower than
a Subaru WRX STi. When we set the spring rates for those cars, and we don’t
have the actual spring rates for them, we use a formula, a mathematical model,
to automatically tune those numbers for us. Then we put in critical damping,
and offset damping with “goodness,” ranking cars by region. A lot of this we
call “automagic”—it’s our voodoo magic that we do in the game, and it’s the
only thing that makes it possible to tune 9,000 numbers on 300 cars.
Proving that this automagic model could work to tune the cars was a big part
of our getting the green light for version one. And there’s a ton of testing that
goes on. We list and graph the numbers we get, looking for anomalies, and
then we test the cars by hand. For example, one may come out with a really
loose spring rate. Sometimes we find that our formula isn’t taking weight
distribution into account as well as it should. Then we rework the formula,
reexport all the cars’ values, and retest. That’s a lot of systems—engine systems,
such as turbo pressure, rpm, inertia, and so on. Some things we get to research
a lot, like all of our stock turbo pressures. We went through and tested them,
and made sure that they were in the right stack rank relative to each other and
that their results in the game matched our research and knowledgebase.
After the automagic has done its thing, then you go in and hand tune.
For instance, getting the nuances of the suspension right is less about oversteer
and understeer and more about controlling the car with the throttle through
a turn; how getting onto, off of, and back onto the brakes creates oversteer;
how braking and throttle techniques affect the car. We’ve got a really good
team—guys who are rally drivers, guys who have driven all kinds of cars. So
we start tuning that way. But inevitably there are cars no one on the team has
driven, like the Lancia Stratos. We had trouble finding reviews on it; we just
knew it was a famous rally car, but our physics got a ton of that stuff right.
You start putting in the weight distribution, the size of the car, its moment of
inertia, and it starts getting better and better.