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How Lucky's Tale Avoids Making Users Sick

It's difficult to avoid sickness with a moving camera, but Playful did it by compressing the camera's range of motion, focusing the user's attention on a single point, and experimenting with all types of designs.

Lucky’s Tale is the flagship game for the consumer version of the Oculus Rift, currently in development by Playful Corp. At Oculus Connect last week, Dan Hurd and Paul Bettner shared some of the things they’ve learned while building it.

Lucky's Tale Screenshot

As the flagship game, it’s being designed for everyone to enjoy, which means that the developers must work very hard to avoid making people feel sick while playing the game for extended periods. Hurd and Bettner shared some of their tips for helping avoid sickness.

Camera Movement is Everything

“Camera movements are extremely finicky,” Hurd said. “We’ve been playing around with them for a year” (my emphasis added). Small changes in the movement of the camera have the ability to make people feel very sick, or not sick at all.1

This is because a third-person camera will always violate the best practice recommendation that acceleration should be controlled by the user. It turns out that there’s a lot that can be done to mitigate this however, and we’ll investigate some of these steps.

If You Can’t Change the Camera, Change the Level

The camera must follow the avatar wherever the avatar goes. If excessive camera movements make the player sick, limit where the avatar can go so the camera can’t move too far. The Playful team followed this approach in Lucky’s Tale, making the levels play out in a straight line, with the camera following. Here’s an example level. You can see that Lucky can only move along a narrow platform.

Narrow level from Lucky's
Tale Narrow level from Lucky's Tale. Source: The Rift Arcade

A Focus Point Can Alleviate Sickness

Camera movements make people sick. But players tend to notice movement less if they are focused on an object in the game, says Hurd. In this case, users are focused on Lucky the whole time they are playing, and with Lucky as a focal point, the camera movements don’t cause as much sickness.

Make Everything Really Small

Playful’s developers wanted to make Lucky run and make moves at a fast pace. Initially, Lucky was about five feet tall, with a camera positioned above Lucky. When Lucky ran, the camera would have to cover a lot of virtual ground, causing people to get sick.

Instead the developers “shrunk” everything down, to a scale equivalent of Lucky moving around on a virtual tabletop in front of the user. This way, camera movements are not nearly as dramatic, and the user doesn’t feel as sick. You can observe this effect in the walkthrough below, where Lucky feels as though he’s three feet in front of your face.

Test Lots, Mostly People Who Get Sick Easily

After making changes to the game or the cameras, Playful will test on their chief financial officer, who is very prone to getting sick. If he gets sick right away, they know that they need to go back to the drawing board and remove the component that’s causing sickness.

It’s not a perfect proxy, and the CFO in question is probably becoming accustomed to the game, but in a world where random users might not tell you how sick they are, and it can be expensive (in time, if not money) to recruit people to come into the office for each round of testing, finding someone who you can run tests with frequently is an okay heuristic for sickness in the general population.

Try Everything

The Playful developers will try anything, which is how they found the best practices described above. They tried 30 or 40 different prototypes before they landed on Lucky’s Tale. According to Playful, they don’t know (and can’t guess) what’s going to work in virtual reality and what won’t, so they just try everything they can and see what looks good.

This approach is also being taken by Josh Carpenter and the Mozilla team, as they try to figure out what Firefox and the Web mean inside a VR headset.

1. I was somewhat relieved to hear this, having been widely panned for writing about why porting third-person platformers will be nearly impossible.