Virtual reality overcoming the barrier of motion sickness
Virtual reality is currently seeing incredible momentum as a rapidly emerging consumer technology with wide reaching industry applications from the classroom to the workspace. However it cannot be denied that there are several obstacles that remain in VR’s trajectory which need to be overcome before we truly see this technology reach mass consumer adoption.
The biggest of these is motion sickness.
Why do we get sick?
In the past when humans roamed the wild in search of food it would not have been uncommon to consume poisonous substances. The human body has a number of mechanisms to combat poisoning, one of which is to trigger nausea so you can either vomit or sweat out the offending toxin. If the brain senses any sort of sensory and visual disconnect (such as when we consume too much alcohol) motion sickness is felt and the brain triggers nausea to help purge the poison from our body. It is a theory that VR triggers this ancestral defence mechanism with visual & sensor disconnects.
How do we get sick?
Motion sickness can be triggered from a wide spectrum of situations, including rollercoasters to car journeys, boat rides to simply spinning yourself on the spot. And while research is helping us understand how to identify motion sickness triggers, it is still unclear as to exactly what happens in the body to cause motion sickness and its unpleasant side effects.
The leading theories around how motion sickness occurs include;
- Eye & Ear Mismatch Theory: Also known as visual vestibular inner ear conflict. Your brain interprets motion by matching data from your eyes and your ears together. If there is a mismatch in that data it can throw the brain off and trigger motion sickness. In VR while your eyes might be sending data to your brain that they are perceiving motion your ears are sending conflicting data that no motion is occurring.
- Locked Eyes Theory: Also known as vestibular ocular reflex. When you look at an object, your eyes lock onto it in the world space. Even if the object moves your eyes track the object while your head can remain still. VR in its current form does not allow for eye tracking which means the user is forced to move their neck to look around a space. If you try to do this in the real world you will quickly see how this is both uncomfortable, disorienting and can lead to motion sickness.
- Static Environments Theory: Your brain uses static reference points from your environment to calculate motion both of self and of other objects in your vision. These reference points include things like a horizon line, the floor below you or the ceiling above you. If you were to take those static reference points away, for example by putting someone in a constantly shifting space the individual would suffer from motion sickness as the brain fails to find references to judge motion. If VR experiences are poorly designed or poorly optimized ‘judder’ or shaking environments can occur triggering motion sickness in the user.
Although a deeper understanding is needed in the field of motion sickness more importantly is a need for best practices to ensure VR experiences do not trigger motion sickness in users. So how do we combat motion sickness while designing VR to ensure our experiences appeal to the widest possible demographic? There are a number of techniques designers can employ to ensure experiences appeal to the highest spectrum of VR users;
- Keeping the experience at a constant 90 frames a second; the human eye can begin to experience judder if an experience drops below 90 fps which in turn can trigger motion sickness. Rendering VR is a very intensive job for any computer and needs a very high end graphics card to do it properly. But it is the designer’s job to ensure an experience is built properly from the ground up and optimized to guarantee each and every second of the experience is clocking in at 90 frames. (Times two)
- Keep motion in VR slow; Normally a video game characters runs at speeds of 40 – 50 km/h which might look pretty on a flat screen monitor but are recipes for motion sickness when injected in VR. Motion in VR experiences need to be kept at very slow speed limits in an effort to mitigate nausea.
- Keep motion in VR constant; interestingly although the inner ear is very sensitive to changes in direction and acceleration it has no ability to sense constant linear velocity. This means designers need to ensure VR experiences with motion build experiences with linear motion in mind keeping changes in direction to a minimum or done at very slow speeds.
- Keeping motion in VR stable; building on the above point, designers need to be careful using drastic motion such as rotation or sudden changes in direction, backward motion or strafing. Fading to black for a moment and fading back mimics the blinking of a human eye and can help users experiencing shock when direction changes happen.
- Placing the user in static space; a static environment allows the eye a point of stable reference when experiencing motion. Placing the user inside something like a cockpit, elevator or other static structure while moving through a space helps reduce the potential of motion sickness greatly.
- Real World References; giving the user real world anchor points to physically reach out and grab that are also rendered in the digital world, such as hand railings or door handles help anchor a user in the digital world and reduce any sensation of disorientation.
- Never control the users head; in popular storytelling mediums such as film or video games controlling where the user is looking is a common tool to keep story progression. This technique should never be employed in virtual reality. Controlling the motion of the users head is a one way ticket to nausea.
- Keep experiences short; experiences at this early stage in VR as an emerging technology are best kept short with durations of between 3 – 10 minutes. Anything longer than this should allow for users to take a break. As VR becomes more common place users will build up their ‘sea-legs’ and become more resilient to any form of nausea meaning durations can increase.
While a lot of research is being conducted into mitigating motion sickness in virtual reality the responsibility ultimately lies with the VR designers to ensure they build out their experiences using tried & tested design techniques that bring the risk of a user experiencing motion sickness to the lowest possible levels.