How virtual reality really works

So, what is it about VR that's got everyone so excited? With your headset on, you experience synthetic scenes. It appears 3D, it feels 3D, and maybe you even have a sense of actually being there inside the virtual world. The strikingly obvious thing is: VR looks and feels really cool! But why?

Immersion and presence are the two words used to describe the quality of a VR experience. The Holy Grail is to increase both to the point where it seems so real, you forget you're in a virtual world. Immersion is the result of emulating the sensory input that your body receives (visual, auditory, motor, and so on). This can be explained technically. Presence is the visceral feeling that you get being transported there—a deep emotional or intuitive feeling. You could say that immersion is the science of VR and presence is the art. And that, my friend, is cool.

A number of different technologies and techniques come together to make the VR experience work, which can be separated into two basic areas:

• 3D viewing
• Head-pose tracking

In other words, displays and sensors, like those built into today's mobile devices, are a big reason why VR is possible and affordable today.

Suppose the VR system knows exactly where your head is positioned at any given moment in time. Suppose that it can immediately render and display the 3D scene for this precise viewpoint stereoscopically. Then, wherever and whenever you move, you'll see the virtual scene exactly as you should. You will have a nearly perfect visual VR experience. That's basically it. Ta-dah!

Well, not so fast. Literally.