As I traveled around the world with the HTC Vive and Oculus Rift, universally first-timers would be fascinated, but a bit woozy after trying VR. What contributes to this? One possibility is the vergence-accommodation issue with current displays. However, the subject of this post is locomotion and the anatomical reasoning behind the discomfort arising from poorly designed VR.
With VR you typically occupy a larger virtual space than that of your immediate physical surroundings.
So, to help you traverse, locomotion or in other words a way of sending you from point A to point B in the virtual space was designed. Here’s what this looks like:
Caption: This guy is switching his virtual location by pointing a laser on the tip of his controller to move around.
Movement with changing velocity through a virtual environment can contribute to this overall feeling of being in a daze.
That’s why most creators smooth transitions and avoid this kind of motion (i.e. blink teleport, constant velocity movement from Land’s End). Notice how the movement seems steady and controlled below?
Acceleration and Velocity
‘Acceleration’ is, put simply, any kind of change of speed measured over time, generally [written] as m^-2 (meters per second, per second) if it’s linear or in rad^-2 (same but with an angle) if it’s around an axis. Any type of continuous change in the speed of an object will induce a non-zero acceleration.”
The Human Vestibular System
When you change speed, your vestibular system should register an acceleration. The vestibular system is part of your inner ear. It’s basically the thing that tells your brain if your head is up or down, and permit[s] you to [stand] and walk without falling all the time!
Fluid moving in your semicircular canals is measured and the information is communicated to your brain by the cranial nerves. You can think of this as [similar to how] an accelerometer and a gyroscope works.
[This] acceleration not only includes linear acceleration (from translation in 3D space), but also rotational acceleration, which induces angular acceleration, and empirically, it seems to be the worse kind in the matter of VR sickness…”
Now that you have this grounding for our anatomical system of perceiving acceleration the upshot is that often viewers in VR will experience movement visually but not via these semicircular canals. It’s this incongruence that drives VR sickness with current systems.
Some keywords to explore more if you’re interested in the papers available are: Vection, Galvanic Vestibular Stimulation (GVS), and Self-motion.