How do cars end up in games?

Back in the good old Atari 2600 days, replicating a car in a computer game was a simple matter. A vaguely vehicle-shaped blob formed of a few dozen blocky pixels, and a buzzy ‘engine note' soundtrack that rose and fell with no relation to your speed? Good enough for us, ta.

But today, gamers want rather more. Demand it, in fact. 

You want to feel the car reacting to your inputs, as it would in real life. To see it fall to bits when you sadistically smash it up. And to have the latest models available to download as soon as the sheets are pulled off them at a motor show.

So when the team behind Forza Motorsport 5 picked the McLaren P1 as its in-game halo car, it presented a few immediate challenges for Dan Greenawalt, Turn 10's creative director. Mainly because the P1 wasn't yet finished, but also because the hybrid hypercar pushes the technological and dynamic boundaries of what a car should be able to do (as Jeremy recently found out). So where the hell did he start? We wanted to find out, so grabbed some time with him on a recent trip to London.

"Everyone thinks that getting a car in a game is all about 0-60mph and numbers," Dan says. "But it's not. It's all about physics." And, as it turns out, ‘making' physics is no simple process.

"Firstly, we want to get our hands on the car," says Dan, a self-confessed science geek. "Then every single variable needs to be isolated, so it can be recreated digitally in real time."

This means an exhaustive automotive dissection. Every single individual part of the vehicle - from suspension components to panels to exhaust bolts - is weighed, and its output measured, in order to see where the limits are and how the car performs.

If Turn 10 can't physically get the part, they speak to the original company that made it, not the car's manufacturer. Then they have to figure out the car's moment of inertia, the weight of the driveline, how much flex there is in the chassis, the length of the top and bottom A-arms, the angle of the suspension, plus lots, lots, lots more.

The level of detail is faintly insane. For instance, when gathering info on tyre reactions for Forza 5, Turn 10 shipped every tyre on sale to a company called Calspan, who carried out weeks of tests to see how each would react in different conditions and loads, and at a diverse range of temperatures.

After all that, Calspan gave Turn 10 millions of ‘data points' -more detail than tyre companies have on their own product, unbelievably - which he fed into Forza's database. Which is why, during a Stig-spec drift round the Hammerhead, the tyres will go off in the same way in Forza they will in real life. And you'll end up in the grass, just as you will in real life.

But as the P1 wasn't finished when Turn 10 were building the game, Dan's team couldn't get their hands on the car. But with the help of McLaren's engineers, they were able to make a perfect digital recreation.

When a part or system was updated in the P1's development process, the McLaren engineers would send CAD data, photographs and simulations across to Turn 10's base in the US, where the digital car would be updated in unison with the real thing. We can safely assume this data transfer was encrypted with a level of security to make the Pentagon's deepest secrets look like an unlocked bike-shed.

But how can the visceral sensation of driving be translated through a little control pad with some buttons on? "We can't recreate the Gs you feel, the way your butt helps read the road, or the feel you get through the pedals and wheels," Dan admits. "But what you feel through the vibration in the controller are the jitters and bumps that'd you feel in the real thing."

But, of course, there's more to producing a car in-game than just matching the physics. It needs to look and sound realistic, too.

"We use dynos to catch sound," Dan says. "Dynos are all around the world, so we can put cars on them easily. Once on the dyno, they mic the car to death so different sounds can be isolated. This is because if for some reason they can't get a car on a rolling road, they research its specs to find out what the opposition of the cylinders are and its firing order. Then they patch together a sound of the plenum from a similar but completely different car, the exhaust sound from another, and the intake noise from another again. Once blended together, your brain will be tricked into thinking it's the real thing."

As for the visuals, well, to some extent that's the easy bit. When Forza started a decade ago, Turn 10's boffins had to photograph, measure and then painstakingly recreate every car. Nowadays manufacturers simply send Dan their CAD drawings of each model. They're entered into the database, and the cars emerge millimetre perfect.

That said, for some rare cars it's still a case of stitching together thousands of photographs and videos to build the car up in pixels - like the good ol' days. But with all the technology now available, Dan reckons it's possible to make a car look too perfect.

"We found that the ‘Autovista' cars in Forza 4 were incredibly detailed but they looked too digital," he says. "For Forza 5 we learned that to make things look real, they need imperfections: scratches, dust and dirt etc. That's what the human eye is used to."

Manufacturers used to be reluctant to put their cars in games, but now they're more than happy to give developers access to boxes and boxes of CAD and engineering data to get their latest model into the virtual world.  Why? Because it's an incredibly effective way to sell cars and build brand awareness.

"We proved unequivocally that Forza sells cars," Dan says. "We've had dealers tell us that they've sold cars within a week after someone had driven that car on Forza."

Such fanaticism isn't limited to mass-market stuff. Oh no. After a Forza demo at the E3 gaming convention earlier this year, Mclaren received orders and full down payments for two P1s from gamers who had played the game and loved the way it looked and drove.

And, since they're all now sold out (sorry), the virtual world is as close as us non-millionaire mortals will ever get to the P1. Good thing it's getting closer all the time.