This is where I share a few terms that you’ll find used in the VR community, and a few I may have made up myself!
Active VR: Any first-person application that features natural human locomotion, i.e. walking, jogging, running, and turning. The most popular and critically acclaimed videogames of the pre-VR age featured this type of locomotion.
Verse: Shortened form of ‘Virtual Space’. Can refer to any area of the virtual world, or the medium of VR more generally (‘The Verse’). First coined by Professor Tristan Verstraeten AKA ‘Doc V’.
Versing: Engaged in a VR program. Example: ‘Versing like a Boss’.
Versed: Having first-hand experience of VR. Example: ‘He/She is well versed’.
“While versed” – while engaged in VR.
“It’s been versed” – It has been adapted for VR.
“It’s versable” – you can play it in VR/natively supports VR.
“I’m so versed right now!” – I’m deeply immersed in VR.
Simulator-sickness (sim-sickness): Involuntary response characterised by symptoms of discomfort, nausea, and dizziness. It is a natural safety mechanism experienced when our brain detects a disharmony between our visually perceived motion and our internally sensed motion. The purpose of this response is to stop us in our tracks to avoid any potential harm (such as losing our balance). In the case of simulator-sickness, this disharmony is the result of an apparent self-motion that is seen but not felt; as opposed to motion-sickness which is brought on by self-motion that is felt while our vision indicates we are stationary, as one might feel at sea.
Kinesthesia: Made up of the vestibular system and proprioception, this is our internal ability to sense the motion of our body in and through space.
Vestibular system: A sensory system located in the inner-ear by which we are aware of our head’s rotation, acceleration, and angle relative to the direction of gravitational force.
Proprioception: Our body’s natural positional tracking, provided by a network of nerves integrated into our skeletal muscles, tendons, and joints. These allow us to know the relative position and (by extension) the manner of movement of our limbs, without needing to look at them. Even if we are not consciously aware of it, our subconscious can differentiate between the type of movement that we are seeing in Virtual Reality (say, running forward) and whatever motion we may be doing to trigger it (for instance, jogging on the spot) if they do not align closely enough. To prevent sim-sickness therefore, an omni-directional treadmill must allow us to replicate the various locomotive gates we employ in real life, such as walking forwards, backwards, and strafing. Picking-up of the feet to effect a stride is one of the requirements. By virtue of leaning forward, backward or to the side to create these movements, the vestibular system experiences acceleration, which further helps to alleviate sim-sickness. The world’s first consumer omni-directional treadmill to emerge on the market was the Virtuix Omni, which launched on the 15th of December, 2015.
Omni-directional treadmill (ODT, VR treadmill, or just ‘treadmill’): In contrast to a uni-directional treadmill (currently the standard type) which allows the user to only move in one direction, an omni-directional treadmill allows the user to turn and move in 360 degrees. This is essential for VR, since it is an immersive medium in which content can appear on all sides of the user; unlike older media in which the content is typically in front of the user the whole time. Attempting to turn the avatar around while the user remains facing forward has been shown to trigger sim-sickness, often described emphatically as ‘poison’ due to its ability to induce instant nausea. While comfort modes can be used to change the avatar’s position or angle without inducing sim-sickness, they do so at the cost of presence – defeating the purpose of VR.
Comfort modes: Comfort modes take the opposite approach from omnidirectional treadmills in their effort to eliminate sickness. Where an ODT adds immersion and synchronises real and virtual movements together to avoid disharmony, comfort modes deliberately reduce either immersion or presence. By reducing immersion they eliminate vection, which is the visual trigger that leads to simulator sickness. However, in practice the results appear to be inversely proportional - comfort increases only as far as immersion decreases. Examples include blurring the image, overlaying a static mesh, reducing the FOV, and switching to a third-person view. Another method is to remove the sense of presence which users get from moving through the virtual world. This involves switching instantly to another viewing direction (instead of turning your head), or teleporting directly from one point in space to another, rather than moving continuously through it. This is not how people originally imagined VR would be, and there is concern that it may hamper the uptake of VR, though comfort modes remain the only current alternative for people without an omni-directional treadmill.
Vection: A visual illusion that you are moving through space when you are not. This can happen in real life, a typical example given is when a train passenger looks out of the window and sees another train on the opposite track pulling away. Because it fills their field of view, the passenger feels that they are the one moving, and not the other train. As that train is pulling away slowly, this does not induce such an uncomfortable feeling, however vection that occurs at higher speed can. This is what happens when you move your character in VR while you remain in one place.
Developers have found that when this movement is initiated using a keyboard or gamepad, it is known to trigger sim-sickness, especially at higher speeds. Some developers have chosen to significantly reduce the maximum speed of the avatar to mitigate this, as an alternative to comfort modes, though by enabling proper proprioception and vestibular feedback with an omni-directional treadmill, vection ceases to be a problem, and the player can run as fast as they like without issue (as the author has done on numerous occasions!).
Social VR: Simultaneous multiplayer VR experiences. Predicted to be a huge attraction, and probably deserving of a longer paragraph!
Seated VR: VR experienced without a VR treadmill, often limited to static experiences or presence-reducing comfort modes.
Standing VR: VR experienced standing up. Standing helps with immersion and of course can be had without a treadmill if the experience is static in nature or of limited area. Otherwise, comfort modes are required to navigate due to simulator sickness and the space constraints of a room. There are also safety issues due to the risk of losing balance or tripping over a cable or coffee table.
Room scale VR: Usually referring to standing VR experiences where a tracking volume is present. Walking through the room is tracked and mapped to the avatar. While effective, without a treadmill the VR experience is limited to the area of the room, unless comfort modes are used – for instance frequent teleporting. Though such tracking works perfectly for small tech-demos, it does not enable the most popular videogame genres which include first-person shooters and open world exploration games.
Infinite scale VR: A way of describing the ability to roam endlessly in any direction, perfect for open world games. Possible indoors only with an omni-directional treadmill.
HMD (head-mounted display, goggles, helmet, headset, mask): A HMD (I prefer to say mask, for its verbal brevity) is a wide field of view display worn over the user’s eyes, which in tandem with head-tracking creates the illusion of being enveloped in a virtual world. One of the primary virtues of an HMD is that objects can appear to be a true-to-life scale, as opposed to whatever size (typically smaller than real life) it would be represented on a screen that is further from the user’s eyes. This effect is hard to communicate, and often people are not convinced of the benefits of an HMD until they try one, at which point they see its potential as part of an empathy machine.
Empathy machine: The idea that by immersing someone in Virtual Reality, they can be emotionally moved by what they see, potentially leading to changes in behaviour and even social change, in addition to new types of entertainment content becoming popular. Compared to non-VR media, the user accepts what they are experiencing as though it were happening in their immediate space, rather than feeling that it is unreal, or happening in a place far removed from them, a factor known to make it harder to feel empathy. This is due to the effects particular to HMDs - correct scale, large field of view, head tracking, and stereoscopic 3D.