Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

On Monday, we took a look at a pretty cool office. On Wednesday, how to make a fake car sound real. Earlier today, a Jalopnik-liveried Shelby. Now, we look at the guts of Forza's digital world. Welcome to the machine.

This may sound obvious, but a video game is not the real world. On the surface, that statement seems simple: If you're a game engineer, you have ultimate control. Want to build a place where an Italian plumber rides a dinosaur and chases after floating money? Gravity and testy steamfitters won't stop you. Think Nazi zombies with glowing eyes are a great way to get your war on? Screw the metaphysical issues and make it happen.

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

Simulators, naturally, are the exception. Because they attempt to accurately replicate the world we live in, they are both of gaming escapism and apart from it. Building a sim is not for right-brain thinkers or the detail-averse — when you try to assemble a fake environment that doesn't feel fake, you live and die by the little things.

Dan Greenawalt cares about the little things, but above all, he just digs cars and physics. Greenawalt is the lead game designer for the Forza Motorsport franchise, and he is exactly the kind of guy you expect him to be. He loves cars, he loves games, he geeks out on books with titles like Race Car Vehicle Dynamics, and phrases like "meanest-looking sonofab*tch car you've ever seen" roll off his tongue on a regular basis. He gets it, and he is one of the main reasons why Forza does not suck. We talked to him and his team about how the game came to be.

The Beginning

The Forza franchise has its roots in the beginning of the Xbox, and it was essentially the first Microsoft game to be developed in-house in Seattle. The Xbox was launched in 2001 with a handful of flagship titles, one of which was the Microsoft-published, arcade-oriented Project Gotham Racing. Greenawalt worked on Gotham, and the experience prompted him to pitch Forza — and an in-house studio team to produce it — to his bosses in 2002. They bit, and Turn 10 Studios was born. The original team was composed of just ten people. "We had really well-laid long-term plans [for the game]," Greenawalt says. "We haven't stuck to them at all."

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

The Philosophy

Greenawalt: "The heart of the pitch was that we didn't want to be another Gran Turismo. We wanted to bring something else to the table; we wanted to make it about our culture, our way of seeing cars. We wanted to give it depth beyond just driving skill, we wanted to not focus everything on the driver, and we wanted to get new people stoked about cars." Things like livery studios, an active dialogue with the game's fan base, and realistic vehicle modifications grew out of this approach.

"What makes me a better designer is that I'm not really a good race-car driver. I look at these things like most people look at them, like my wife or family looks at them. Do I like the tech side? Yeah, because I'm geeky. But I think that if I was just all about being a pro racer, if I was that narrow-minded, the game [would suffer]. The idea isn't to capture this audience or that audience, but to appeal to all of them."

Turn 10 content director John Wendl: "We believe that everyone is a car guy on one level or another."

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

The People: Obsessed Would Be Putting It Lightly

The Turn 10 crew is a pretty diverse bunch. If you have even the slightest interest in cars or gaming, you feel immediately at home. One guy has a desktop full of Hot Wheels. There is a dude just out of college who made his own Subaru engine T-shirt — it says "boxers do it sideways" — because he couldn't find a company that would sell him one. Wendl is a Spec Miata guy and former professional motorcycle racer, and speed junkies (daily-driven Lotus Elise and track-rat Dodge Neon owned by the same guy?) are everywhere you turn. Some are nuttier than others, but they all seem to love their jobs.

Game freak plus car freak equals pretty entertaining. While I was in Redmond, someone used the phrase "sh*ts noise out" when referring to a car. Half an hour later, I was sitting at a table listening to people crack wise about Volkswagen Quantum Syncros and the Super Nintendo game Starfox. At least five people stopped and stared at an Alfa Romeo Milano in a parking lot on the way to lunch. ("Dude! Track belts!") Unsurprising fact: Much of the office reads this site. They know our in-jokes. They like what we like. It's like they're in our heads.

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

The Physics: Math, Math, and More Math

The heart of the game is a program called Automagic. It allows Forza to offer over 400 accurately modeled cars without requiring that Turn 10 physically test and reverse-engineer each vehicle. Hundreds of data points — everything from moment of inertia and center of mass height to braking distances and a precise torque curve — are fed into the program, which then extrapolates out a digital performance model, calculating any missing information. "It's actually really difficult getting a complete set of numbers, [even with manufacturer help]," Greenawalt says. "There's almost always a game of telephone going on, and things are always rounded one way or the other by marketing groups or lawyers."

According to Greenawalt, Automagic is accurate enough that it has actually revealed flaws in real-world cars. One of those cars, he claims, is the Ferrari Enzo. Turn 10 modeled the Enzo shortly after its introduction — and before anyone outside Ferrari had driven it — using data obtained from Maranello. When the car was loaded into the game, its chassis balance was supposedly nightmarish, a mix of low-speed understeer and snap oversteer. "It didn't work below [triple-digit speeds]," Greenawalt says. "We thought, 'This is the Enzo — it can't be this bad.' We just assumed our math model was wrong." Shortly thereafter, several major car magazines drove the car and commented at length on its flawed handling. Greenawalt was nothing if not relieved.

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

A car takes about six months of man-hours to build. A track takes approximately four man-years. In other words, one car equals enough work to keep one man busy for six months. (Yes, that labor is divided up among a team, so a track doesn't actually take four years.)

For the past ten years, most driving sims have been built around the same math. Nearly every seminal title, from Grand Prix Legends to GTR, has had at least a passing acquaintance with a tire model known as Pacejka's Magic Formula. It's essentially an

Inside Forza Motorsport, Part III: The Physics Of Driving Games

intelligent bit of math that, if you plug in the right variables, allows you to accurately depict the behavior of a tire carcass under load. Turn 10's engineers tried it, only to later throw it away because it didn't spit out results that matched their research. (Toyo, Michelin, and Ferrari all contributed confidential tire data — things like deformation and heat response — to help make the game happen.) The solution was a unique, built-from-scratch tire model, one that accurately depicted load sensitivity and offered more realistic responses to weight transfer. (We're still geeking on the sidewall flex in the Datsun 510 above, but then, we're simple.)

The game adjusts how much it helps your inputs based on which controller you use. Steering wheels get the least amount of assistance. Driving a car with two fingers — i.e., digitally — is hard, and if you tried it in real life, you'd probably kill yourself. Basically, Forza reduces joystick/wheel and button/pedal sensitivity with speed. Be thankful for the help. Pointless crashing sucks.

Greenawalt: "There's this idea that driving games are either/or — you can have accurate physics or interesting and easy gameplay. I just see that as a poor designer's problem. I enjoy the nuances. I like physics. It's the happy place; it's simple. Gameplay is complex. The physics should never be interfered with."

Inside Forza Motorsport, Part III: The Physics Of Driving GamesS

The Cars: Bug Not The Decider

One man decides which cars make it into the game. He's an intelligent individual who loves cars, likes physics, and has a deep knowledge of automotive history. No, we won't give you his name, because then you'll start bugging him. Just know that he listens to your requests.

A car's image and interior can be added to the game in one of two ways. The preferred method involves an armature-mounted scanner that builds a three-dimensional picture of a car by physically examining it. If scanning isn't possible, a digital model is assembled from detailed photographs.

The Jalopnik-liveried 1968 Ford Mustang GT500KR: You like it. Admit it. It is strong like bull. That is all.