Pixels and Polygons

David Vespremi, October 4, 2007

So there it was. With a strange sense of accomplishment, I took it all in. The silver Roadster’s windshield was smashed, spider web cracks fanning out in all directions from under the mono-wiper. Along the driver’s side of the car, from nose to tail, the paint had been scraped away by what only could only have been severe contact with a concrete barrier. Checking out the passenger’s side, the damage was just as bad.

Smiling, I responded, “this is great!” and took a moment to reflect on how we got to this point. For those expecting a crash test blog entry outlining the rigors of safety certification, I’m sorry to disappoint. The same can be said for those hoping to read of a track testing catastrophe.

No, the damage I was surveying on the 2008 Tesla Roadster was entirely the doing of a team of designers and programmers manipulating pixels and polygons in the wee hours of the night in Liverpool, UK. The devastation was complete. The end result, entirely impressive.

The Tesla Roadster takes some scrapes in PGR4

For those wondering how a prototype vehicle that has never been put through its paces by the car magazines, let alone handed off to customers, ends up in a videogame: In many ways the process is every bit as interesting of a logistics and product development challenge as building the car itself.

Once the decision had been made to support Microsoft Game Studios with the opportunity to include the Tesla Roadster in Project Gotham Racing 4 (for the Xbox), what can only be described as a small army of creative folks from all disciplines – including sound engineering, programming, CAD modeling and design – all teamed up to make the vision a reality.

We began with the car itself. It was important that the car look, sound, and drive like the real deal. Now long past the days of Pole Position and Spy Hunter, current arcade style driving games are equal parts simulator and amusement park ride, blurring the line between duplicating the actual sensory experience of racing a car and the over-the-top Hollywood style crashes and collisions. In short, whether skewed more towards the entertainment side of the equation, or towards a simulator experience, today’s crop of videogames are powered by logic engines that can manipulate enough data to make your old Atari or Colecovision seem like a Model T compared to an ... ummm... Tesla Roadster.

The Look

We removed the door to get a better interior shot

In order to have the Roadster look as realistic as possible, Microsoft Games Studios asked for all of the CAD drawings and schematics that could be dropped directly into their modeling program to begin generating the gaming model of the car. There was just one problem – there was no way we would turn over working files on a car yet to be built. The risk to Tesla Motors of a leak was simply too high. There was, fortunately, a work-around: photography. Hours and hours of photography.

In order to build the most accurate models of the car, we were able to work with one of the more recent prototypes, specifically Validation Prototype 1 (or VP1, the dark green car,) and to book time in a high-end studio where every last detail of the car could be photographed and eventually drawn for the game. Because the Roadster is an open-top car, it was important that every last nuance, texture, and surface on both the car’s exterior and interior be captured as accurately as possible. No stitch in the upholstery nor lug bolt on the wheel was too insignificant to escape the photographer’s lens. Every detail was captured and a shoot that began early one Saturday morning stretched through the weekend into Monday morning (when our own engineers needed the car back for actual development work).

The timing was tight, but with the photos uploading to an FTP site, scheduling began on getting the sound right.

The Sound

Although commonly reported as completely silent, the Roadster actually has a cool, Blade Runner-like whir at speed. Equal parts AC motor rotor assembly and gearbox whine, the sound of the Roadster is far more complex and full of character than the mere thrum of tires on the pavement and whistle of wind rushing around the seams of the body.

However, duplicating this sound for the game would prove to be an interesting challenge. Having previously worked with sound engineers on incorporating my personal car (an MR2 Turbo) in Need for Speed Carbon, I knew from experience that one way to capture sounds on a moving car is to mount microphones covered in a furry material (designed to minimize wind noise) near the exhaust and the engine and then hit the road. The sounds are recorded to a hard drive on board the car, and, by placing boom mikes on the stretch of road on which the car would be driving, the engineers can match the sounds as heard both from the source as well as on the road.

The Tesla Roadster wired for sound

With the MR2, the result is an impressive collection of sucking noises from the air intake doing its best impression of a vacuum cleaner, the fan-like spooling of the turbo, the roar of the exhaust, and the periodic venting of excess boost pressure in a loud “pshhhhhhh” sound from the blow-off valve. Add in a bit of valve train noise and the occasional loud scream of a wastegate dumping even more boost pressure, and the mechanical symphony begins to take shape with each component being captured to its own channel and mapped at every point in the car’s power curve. The combination of these, once stitched together in a sound studio, is no less complex than recording the vocals, bass, drum, lead guitar, rhythm guitar, and synthesizer in a studio. Each track is married to the next until everything is perfectly in synch and all the sound levels can be adjusted and optimized.

By contrast, the Roadster is no less interesting but a lot more subtle and elusive in the recording process. Putting aside the fact that there are no traditional mechanical components to assign to dedicated microphones, the challenge becomes fighting background noise (wind, tire, and ambient noise) to accurately capture the sound of our electric sports car. One solution would have been to use Tesla Motors' own motor dyno room, a facility in which the motors are bench-tested under load conditions, to capture the Roadster’s true sound without having to worry about all of the external noise associated with a moving car going down the road at speed. However, this idea was a no-go in that it required not only a spinning motor, but also accurately matching gear ratios to simulate that motor under the same loads that it sees when installed in the Roadster.

Cruising in the Tesla Roadster

The next idea was to use a traditional dynamometer, used to measure horsepower at the wheels, by strapping the car to a giant steel roller and then dialing in the resistance to the roller to simulate the load conditions the Roadster would actually see going down the road. This was better, but still posed problems. The sound of the roller itself (and the car’s tires on the roller) could be enough to drown out the characteristic Blade-Runner sound as the motor revs and speeds climb.

That left one final option, which proved to be the most likely to yield the results we were after. The idea was to use a hub-mounted dyno while removing the wheels and tires from the car so that the load was placed directly on the hub assemblies. With the noise of the traditional steel drum and tires gone, and no wind noise to worry about, we would have what we needed to isolate the sounds we were after. We found a local resource to provide us with the facilities we needed (thanks to WORKS, a high-performance Mitsubishi tuning outfit in San Rafael, California). Late one night, after the prying eyes of customers had left, we snuck the Roadster into WORKS’ dyno room. Once there, we discovered how well this set-up works. While most cars need a large evacuation fan and tubing system to send the potentially lethal exhaust fumes out of the building, with the Roadster we could drive the car to its limit in an enclosed room, without worrying about the noise, carbon monoxide poisoning, or the open bay door that would give prying eyes a peek at what we were up to inside.

The Performance

A perfect rendering

With the designers copiously matching the details of photographs to every dimension publicly disclosed on the Roadster, and the sound engineers busily mapping out the Roadster’s sounds in 1,000 rpm increments, the next component was matching the performance of the car in the game to the real deal. Here, my role was much less hands-on in that all we really had to do was provide the power delivery curve of the Roadster, as expressed in a dyno-graph (which, handily enough we were able to provide not only from Tesla’s engineering team, but also from our recording sessions at WORKS), and the gaming engine would do the rest, seamlessly mapping out the sound and acceleration to the actual torque delivery of the Roadster. After years of development across now four installments of the Project Gotham Racing franchise, we are confident that the folks over at Microsoft Game Studios have a game engine capable of delivering the goods.

And Then We Wreck It

So what of the carnage I mentioned earlier? Like many games in the arcade-genre, PGR4 gives the gratification (or devastation, depending on your perspective) of war-wounds from racing. Each car is allocated a number of polygons (represented in terms of data points in the game) and a crash engine computes the crushing and distress of these polygons from impact events in the game (for example, hitting another racer or a fixed barrier). While the Roadster’s carbon fiber bodywork may not accurately reflect the same type of damage as, for example, the crushing of sheet metal, many of the areas of distress were direct carry-overs, like the shattering of glass and scraping of paint. Further, since the game designers knew where body parts like the rear clamshell were hinged, they could design fenders and other body components to deform on impact just as they would on the car itself.

It's really gratifying to see the end result fully rendered, including the impressive ability to reflect sun, shade, the clouds above, and rain. Check it out for yourself at Microsoft's website – or on your own Xbox. The game went on sale this week!