How Oculus Rift works: Everything you need to know about the VR sensation

The Oculus Rift may look like a relatively simple device but it's actually a pretty amazing piece of kit. The hugely promising virtual reality headset includes a whole bunch of amazing technology designed to create a sense of complete immersion in a three-dimensional world. When you realise what's in there, it's hardly surprising that it's taken this long to come up with a virtual reality system which actually works – and there's still a lot of room for improvement.

With the device still being in 'prototype' stage, the Oculus is always making tweaks. CES 2015 saw the addition of Head-Related Transfer Function technology for 3D audio.

Here we've analysed every single bit of Oculus Rift's Development Kit 3 or "Crescent Bay" as it's been dubbed, from the prodigious headset itself to the lead which connects it to your computer.

Creating 3D gaming environments is a complicated business, even if they’re just going to be shown on a 2D monitor. Add in stereoscopic 3D and it all becomes a crazy nightmare made of formulae and vomit. There is no hard and fast way to create 3D for Oculus Rift, but the nuts-and-bolts basics of it involve spitting out two near-square video feeds to the same screen - think playing a vertically-split-screen two-player game.

The clever bit is that each feed comes from a slightly different angle, so that the player's brain is tricked into thinking that two 2D images are one 3D one. You can experience this by looking at a nearby thing (look at that thing!) and then closing your left or right eye and seeing how the angle changes just ever so slightly.

The games themselves also have to change: motion blur, which has been used for years as a way to simulate speed and reduce strain on the GPU, no longer works. Cutscenes with static cameras induce nausea. A demanding 60 frames-per-second framerate has to be maintained to prevent stuttering and shutter effects.

Video is sent to the Oculus Rift via HDMI, with an optional DVI adapter for laptops and newer graphics cards. It also includes USB, which carries data and power to the device, and lets your computer know what this bizarre gizmo is. This 10-foot cable is just the right length to provide a consistently good signal without any degradation, while remaining reasonably light so you don't feel like a dog chained to a lamppost. Which is great unless you're playing a VR game about being a dog chained to a lamppost.

Development Kit 2's headset also includes a USB port so you could potentially connect a controller, or some USB headphones, or a novelty singing cactus. This increases the power draw of the Rift, so Oculus has chucked in a mains adapter with US, UK, Australian and European plugs which connects to the same junction as the positional tracker.

Tracking the position of your head in 3D space is critical to the way the Rift works. One of the ways it achieves this is with a series of infrared LEDs embedded in the headset, which are monitored by a webcam-like camera placed nearby – Nintendo's Wii Nunchuks work in much the same way. On DK2 you couldn't look behind you when you're in a virtual world because the LEDs fall out of the camera's field of view. That's been fixed on the latest Crescent Bay release, and by adding LEDS into the rear of the headset, Oculus Riftnow offers users full 360 degree perspective.

All this feeds into the headset, which connects to your head via vertical and horizontal straps, with the uppermost strap including the HDMI and USB cable. Further customisation is achieved with two pairs of lenses, which magnify the screen so it fills your field of view. Oculus includes a tall set, for those with normal vision and moderate nearsightedness, and a shorter set for very nearsighted users. Screws on the side of the headset adjust the distance between the lenses and your eyes so there’s space to wear glasses, but Oculus recommends wearing contact lenses if you can.

Within the headset sits a single custom motherboard, which includes an ARM processor and control chips for the LEDs. But the most insane bit here is the “Adjacent Reality Tracker” which was developed independently of the Oculus Rift, but has since become a key component. This features a magnetometer, a gyroscope and an accelerometer, all of which combine to accurately track the rift across all three dimensions of three-dimensionality. The original Adjacent Reality Tracker polled at 250 times a second (250Hz), but the team at Oculus has managed to pump it up to 1000 times a second. The result is tracking of infinitesimally tiny head movements, even if you're on a rollercoaster during an earthquake.

In Oculus Rift Development Kit 2 the screen was essentially an entire Samsung Galaxy Note 3 phablet with the smartphone bits removed, but with the completely useless touchscreen and logo intact. Its 1920 x 1080 HD resolution delivers a 960 x 1080 display to each eye; its refresh rate of 60 Hz keeps things smooth, and a 100-degree horizontal field of view means there’s not too much black space around the edge of the display.

A huge amount of data is continually sent back and forth between the positional tracker, the headset, the computer and its software, and the result is an incredibly smooth VR experience. Adjustments such as brightness and contrast are made via Oculus' software, which also includes the ability to calibrate the Rift, set your height and enter your interpupillary distance (IPD), aka the size of the gap between your pupils. Once you've done all this the Oculus SDK also includes a bunch of natty demos to try out.

The audio

As mentioned in the intro, Oculus gave the headset a massive boost in January 2015 at CES when it announced that an upcoming Oculus Audio SDK would allow the use of Head-Related Transfer Function (HRTF) tech, combined with the Rift’s head tracking to create a sense of true 3D audio spatialisation. This will allow Rift developers to immerse users "sonically in a virtual world, surrounded by realistic sounds in all directions."

"HRTFs simulate the changes to a sound when it reaches your head from a point in space," explained the company. "It does this by referencing data that represents changes that would happen to a sound coming from that direction. There is data for hundreds of points around your head, and the software smooths the audio between those points for a natural sound, regardless of head or sound source position.

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