How Oculus Rift Keeps You From Vomiting

The super-realistic car-racing simulator Project CARS 2 seemed like the perfect game to take from TV to virtual reality. The virtual reality headset Oculus Rift can simulate an environment beautifully, but you can feel some of its limits if you have to do something like walk in a game. CARS takes place in a race-car cockpit, so it would seem to have that problem solved. That's why it was such a surprise to the game's developers when their first experience with the gorgeous visuals and the 3-D rumble of virtual reality racing wasn't pleasant. "We got it working," says Stephen Viljoen, the game director for Project CARS, "and then most of us got sick."

Three years after they first started to try to port the game to Oculus, Project CARS 2 is a stunning—and, for most people, a motion-sickness-free—experience, with dozens of realistic cars and carefully mapped race courses, all of which feel dangerous and exist in real life. The world is rendered in minute detail: The sun rises and sets, rain falls and clears, and cars show damage from minor fender benders. The details, ported over from the successful console and PC versions of CARS, aren't breakthrough—the breakthrough is doing it all in virtual reality without having to reach for a trash can.

"Motion sickness is caused by sensory mismatch," says Tim Hain, an emeritus professor at Northwestern University. "So when you're navigating in space, you're getting information from your eyes, inner ears and your feet, and they should all be seeing the same thing."

It's hard to know why we have evolved to get queasy when we read in the back of a bus or when we watch The Last Airbender in 3-D. But Hain says the best theory still belongs to Canadian astronaut and scientist Ken Money, who postulated that it might be the way the body responds to food poisoning. If you suddenly find your vision swimming while your inner ear registers no motion at all after a meal of scavenged mushrooms, from an evolutionary standpoint, it might be time to purge, and fast. The potential for motion sickness is baked into all 3-D experiences, Hain says. No matter how awesome a flight looks to your eyes, your body and your ears will still be telling you you're stuck in a chair, and that opens the door to getting sick.

Back in the '90s, one of the problems with virtual reality technology was that the headsets couldn't crank out enough images per second to successfully trick the human eye. Hain says even a slight lag between turning your head and seeing the screen change can make you sick. Fixing this meant increasing the frame rate that headsets can crank out, and it took some huge leaps in graphics and processing muscle to make virtual reality happen. The majority of movies run at 24 frames a second, and most rendered console games get by with 30 to 60, but headsets have to take that to a new level. "You have to hit 90 frames a second," says Michael Tsai, an effects artist for I Expect You to Die, a sort of super-spy simulator for Oculus Rift. "Two cameras hitting 90 frames [a second], that's a big challenge."

For I Expect You to Die, one of the challenges was rendering a small circular cursor in the center of the screen in a way that felt natural and didn't make you queasy when you swung your head around to focus on an object. In two dimensions, that's easy, but in three, the cursor needs to land not just at the right place but at the right depth. "The [cursor] moves in 3-D space. You want it to sit where your eyes sit," Tsai says. "If you don't do that, you get a double version of the [cursor] and it looks crazy." Making the cursor travel naturally as it slides over, under and next to objects may have been hard to pull off, but it's a seamless part of the game, and you don't feel any strain or illness navigating I Expect You to Die's world.

The current generation of consumer virtual reality headsets has the horsepower to draw you in, but developers still have to get a lot right—any mistake can make playing a game feel like your taxi driver from JFK is using both feet. "The hardware doesn't make you sick or dizzy, but you can still create experiences that do that," says Paul Bettner, the CEO of the gaming company behind Lucky's Tale, another virtual reality launch that had to deal with the motion-sickness problem.

For Tale, a Super Mario Bros.–like game, keeping players from feeling sick meant limiting the camera moves and giving adequate rest time after a big view swing, allowing players' brains to catch up. It also means a lot of what is awesome about virtual reality—a massive world you can explore by turning left, right, left and right—doesn't really work. Tale, like a lot of virtual reality games, plays on a scale that's closer to an intricate tabletop game than to a massive unexplored space. "Doing a lot of stuff in first person is challenging," says Bettner, who adds that the scale and camera movements were incorporated in large part to keep players from getting sick.

For Project CARS, achieving that goal meant rethinking the visual effects used on a console or PC to make players feel like they were racing at 200 miles an hour. A lot of the subtle movements and camera jerks that made it seem like you were bouncing down the track at Le Mans had to be taken out entirely and then added again. The team found that any camera movement or action that wasn't entirely controlled by the player made people ill. "If you aren't initiating a movement, we had to take it out, and then start again," Viljoen says. "We couldn't leave it out because it would feel dead. So we had to rework how the camera works."

During the three-year development process, Project CARS needed regular input from test players; several gave up on the early versions because the motion-sickness problem was so acute. "We had some guys who were so constantly ill that they gave up and said we'll try it later," says Andy Tudor, creative director for CARS. "Eventually they came back and tried it and said it was the best VR racing game."

Despite the leaps in processing, it's still possible the experience will make you sick. Asians, Hain says, are generally more susceptible to motion sickness than the rest of the population, but the mechanism is extraordinarily complex and varied. (A 23andMe study recently found at least 35 genes at play in susceptibility.) The views may be great. But as Hain puts it, if you can't get your body to feel it, "you still have the seat-of-the-pants problem."