Fighting Simulator Sickness
Even a static screen can cause eyestrain and motion sickness under certain circumstances, but VR is particularly prone to such issues. The term "simulator sickness" has been coined to describe the headaches, disorientation and nausea sometimes brought on by virtual reality and other simulation techniques. The biggest culprit is lag time between the user moving and the video image keeping up, which is mostly a hardware problem. Nonetheless, the Oculus VR team has come up with a Best Practices Guide for software developers to help prevent these problems, as well as to create enjoyable games that are well suited to VR. The document includes advice on how to best handle image rendering, user perspective, degree of stereoscopic 3-D depth, camera movement in relation to head movement, in-game speed and change of motion, placement of user interface and objects, audio, user control, visual design and other technical and design considerations.
The guide suggests a few baselines for comfort, like a simulated walking speed of 4.5 feet (1.4 meters) per second, a minimum frame rate of 60 frames per second (fps), an ideal latency of 20 milliseconds or less and virtual placement of static objects no closer than 1.6 feet (50 centimeters) away from the user. There are also references in the guide to specific Oculus VR software features like distortion shaders, predictive tracking and the Oculus head model that developers can use to improve gamer comfort without having to reinvent the wheel.
It suggests performing user testing with outside users to make sure the game (or other application) is comfortable for a variety of people, not just developers accustomed to the content. The guide also advises developers to include optional user settings, including the ability to change speed, acceleration size, field of view and the effect of collisions, as well as inclusion of a monoscopic display mode that makes the image the same for both eyes (which is supposed to decrease simulator sickness).
Although it's a danger when running around in any virtual world, in part due to the disconnect between what your mind is seeing and what your body is doing, sound design can help decrease the likelihood of simulator sickness. The new Crystal Cove prototype's greatly reduced motion blurring should reduce the possibility of motion sickness still further. There's even some evidence that you can just get used to VR and not get as sick as your experience with it increases.
The Oculus VR team claims that viewing through the Rift may be a little better than staring at a standard flat screen when it comes to eyestrain, since it makes your eyes focus in the distance, which is their natural resting position.