Two years ago, Facebook-owned Oculus quietly began demoing a prototype of a stand-alone VR headset codenamed Santa Cruz. Unlike the Oculus Rift, this prototype didn’t need to be wired to a PC to work. Like the Oculus Rift, it promised an immersive quality that might help people actually understand why they’d want to hang out in a virtual environment, wearing a device on their face.

Now that prototype is coming out. At its annual developer conference today in San Jose, Oculus unveiled the Quest, the official name for the Santa Cruz headset. Oculus plans to ship it next spring for $399.

That puts Quest squarely in the middle of Oculus’s other two headsets: the mobile Oculus Go, priced at $199, and the Oculus Rift, which also costs around $400 but requires a high-powered PC to use. But the Quest headset isn’t just the end result of a product differentiation strategy. It’s a showcase for potentially game-changing virtual reality technology, and part of Facebook CEO Mark Zuckerberg’s lofty goal to get 1 billion people using VR, as he expressed during the event's keynote address.

Oculus

The Quest hardware looks unremarkable from the outside, and it uses the same Touch controllers as the Rift. But there are four wide-angle sensors on the headset that are part of the technology that makes the Quest stand out. The Quest has six degrees of freedom—“6DoF” as it’s sometimes called—which allows your head to be tracked positionally, rather than just rotationally. In other words, you can move, not just look around.

High-powered, wired headsets like the Oculus Rift and the HTC Vive also offer 6DoF, but it’s technically complicated to achieve with a stand-alone headset; the Oculus Go only offers three degrees of freedom. The Lenovo Mirage Solo stand-alone headset, released earlier this year, can deliver some 6DoF head movement, but only within a small area, and its hand controllers are 3DoF.

Usually this six degrees of freedom is accomplished using sensors around the physical room, in addition to sensors on the VR headset. In the case of the Quest, no room sensors are needed. Instead, Facebook VR executive Hugo Barra said, the Quest is using “advanced computer vision algorithms to track your position in real time, without any external sensors.”

The company is calling this technology Insight. The four wide-angle sensors on the headset look for edges, corners, and distinct features in the room around you, and then build a three-dimensional map of the environment. Barra said the headset is calculating an estimate of your head position “every millisecond,” and can even deliver precise tracking in larger than room-scale areas. As an example, the company set up a 4,000 square-foot “arena” at Oculus Connect, where people can use Quest headsets to play a free-roaming version of the Wild West shooter Dead and Buried.

Basically, Oculus is taking a technology that usually requires a bunch of sensors at multiple touch points around a room, and recreating the same experience with just the four sensors on your head, using machine learning and computer vision. It’s doing this using every piece of room info it can grab: floors, ceilings, light, wall art, furniture. There inevitably could be challenges with this; things like super shiny floors and white, unmarked walls could theoretically trip it up. Barra said Oculus has tested Insight in “hundreds of different home spaces” and is confident it will work even in these environments.

The optics in the Quest appear to be the same as the Oculus Go; Quest has a display resolution of 1600 by 1400 per eye. However, the Quest has a “lens spacing adjustment to help maximize visual comfort,” according to Oculus. (While the Go display is good, IPD adjustment is key for a comfortable experience.) The built-in audio on the headset is also supposed to be improved from the Go’s sound, and the Quest has 64 gigabytes of internal storage, up from the Go’s 32 gigs.