Blog: Designing your VR game around motion sickness constraint

The following blog post, unless otherwise noted, was written by a member of Gamasutra’s community.The thoughts and opinions expressed are those of the writer and not Gamasutra or its parent company.
While I was doing some research to investigate how we could use Audio to fight against Motion Sickness in Virtual Reality Games and trying to better identify the causes of this problem in VR development, I realized that Audio by itself cannot solve Motion Sickness but can be used as a tool when designing your game to reduce the motion sickness feeling that could occur in some games or experiences.
During my research, I had come across a few articles in regard to how players could limit motion sickness while playing VR and found that none of them really got to the core of the problem or offered any true solutions to the issue, so I decided to write a blog post on it that would not be Audio related for once, in an attempt to shed some more light on the subject and hopefully help game developers find a better approach when it comes to motion sickness and VR.

What’s Virtual Reality Motion Sickness?
There are different reasons that triggers motion sickness in every day’s life, motion that is felt but not seen, motion that is seen but not felt, or both motions are felt but there is discordance between them.

In VR, we are exposed to the second option, as motion is occurring audio-visually in the Virtual environment but not sensed by the players via their vestibular system. We call that “Visually Induced Motion Sickness” (VIMS). It’s all about Sensory conflict and experience, as the perception of self-motion is built on multi-sensory inputs from visual system, vestibular system, and non-vestibular proprioceptors (sensory receptor which receives stimuli from within the body, especially one that responds to position and movement).
In VR, the user plunges into a virtual world blocking out real world audio and visual stimuli and replacing them with simulated ones, both in three-dimensions, which could indeed both provide a sense of motion that would not be felt by the player’s vestibular system and non-vestibular proprioceptors.
As soon as you have a conflict with the user’s expectation based on prior experience, you have a chance to trigger motion sickness. And that’s why some manufacturers or game developers intend to say that with experience of hours playing in VR, people will eventually get used to it, and the problem will be resolved on its own with time. Similar cases happened back in the days when the first FPS games were released on the market.

I obviously don’t think we should ask players to play VR games that make them sick to solve motion sickness in the future. The key here would be to design our games differently so that the players won’t get motion sick but will indeed get used to experience VR smoothly, and then possibly changing organically the pace and style of VR gaming in the future along with new generations of HMDs, which seems like a much more sensible choice from a game developer perspective.

Additional Factors
There is quite a large range of additional factors than can elicit motion sickness in VR.
Technically, the refresh rate is the most obvious one, as a low refresh rate of images in VR is provocative of sickness. The field of view is another one, as a wide field of view would increase the feeling of self-motion and thus enhance VIMS, such as motion parallax, possibly altering distances and depth, luminosity, etc. The viewing angle in the game can also be a factor of motion sickness.

Physically, having a head mounted device (HMD) on our head is altering its weight and inertia, this alteration could generate sickness when movements are made, even when the pattern of vestibular input is normal for the actual motion of the head.

Building a VR Game Around VIMS Constraints
Beyond the sickness itself, VIMS may create undesirable consequences for the new media industry, as sickness could discourage the use of VR HMDs. We thus, as game developers, should ask ourselves the right questions before and when making a VR game or experience, to make sure it is adapted to the device.
VR game needs to be produced respectfully with all the above constraints in mind, but those technical and physical considerations also need to be taken into account by design, art and audio.
For example, in everyday life, head movements are not provoking motion sickness or disorientation, except when initiated by passive rotation of the body. In VR, head movement during field visual motion (creating a sensation of self-motion) is enhancing motion sickness. By contrast, researches from Teixeira and Lackner (1977, 1979) showed that if visual motion is being experienced along with a little self-motion, then head movements tend to suppress the sensation of self-motion and less motion sickness will be experienced than from simply looking passively. Another aspect to consider is that, the greater visual fidelity of the experienced self-motion, the greater the chances to evoke a greater level of sickness, specifically for experiences that include apparent whole-body motion and that require head movements.
All the above reasons and considerations are why we’ve seen the advent of “static” VR games, without any motion. With no visual motion in a VR game, and respecting the main technical constraints, game developers can create great VR games and experiences with great audio-visual fidelity, aiming for the real-life look and sound to create presence, and unlocking full-positionning design possibilities, using audio cues to make the player turn their head during gameplay. A good example of that would be a turret shooters, take “EVE: Gunjack” as an example. The player takes the role of a gun turret operator, in space, on-board a mining ship. Those Gunjacks need to defend the mining-rig against pirates and opportunist trying to take what belong to the company. The sci-fi setting makes the game appealing, and revives the galaga-style space shooter. There is no motion in the game at all, the only movements are the ones controlled by the players moving their cockpit and weapons to aim and shoot at enemy waves, and head movement with no sensation of self-motion is not provocative of motion sickness in virtual environments. If you would want to create a shooter with self-motion, adding a virtual cockpit around the player to your experience helps against motion sickness, and that’s why we see more dogfighting VR games and experiences coming up, as adding a cockpit would help reducing the visual motion, limiting the sensation of self-motion, but there will obviously be a lot of other constraints to design your game around to make it a satisfactory experience, such as but not limited to, the game setting, the visual quality and realistic rendering inside the cockpit versus outside the cockpit, the depth (that could impact the game setting choice), the luminosity, the audio direction choices (as audio could induce a sensation of motion or rotation), etc.

Of course, the genre that everybody is excited about and looking for, because of the excitement of creating a sense of presence in this type of game, is the first-person shooter. VR from a player perspective seems made indeed for shooters, immersion, experiencing stunning landscape, living exciting things we won’t be able to necessary experience in real-life (and that’s one of the reasons why you see a lot of sci-fi and horror games on those HMDs). The main problem is, with the current HMDs tech available; VR is un-compatible with the FPS shooters as we know it today. If you want to go and make a non-static FPS in VR, then you’d have to make a lot of smart choices, and even with those choices, you have great chance that some people would experience VIMS while playing your game. A game that took this bet and did a lot of great choice in my opinion is Resident Evil 7. The setting fits perfectly the constraints: a scary horror first person shooter, being so scary that it impacts players behaviors: you won’t be rushing during gameplay, moving in the game with slow speed, and thus a slow pace of self-motion (the pace of the gameplay is also being controlled by the developers, as the speed is different if you play in flat screen or VR).

The universe of the game is super dark, both literally and figuratively, so the brightness is low, reducing naturally the depth, distance and FOV visibility in the game. To make sure you won’t be able to see far away anyway, the game takes place in a manor, so you won’t be face to face with some bright stunning landscapes on top of a mountain or the like. While you’re already moving your character at slow speed, the developers from Capcom made sure that in the eventuality you’d want to run in this game (which means you are a fearless person or a bit crazy) your field of view (FOV) would be reduced during motion, specifically the fast-paced ones. There is of course the already proven possibility to teleport in the game instead of walking around in the options, as it would remove any self-motion feeling, though teleport could be a bit disorienting as well. If you made the choice of walking in the game instead of teleporting, the audio footsteps are mixed quite loud, breaking a bit the immersion, but this un-realistic approach is obviously sending information to the player’s brain that he or she is playing a game in a virtual environment, reducing the chances of sickness as well.  
Finally, a no-go in VR game design is moving backwards, and once again, RE7 does that well, they have a quick command to turn around, which becomes more natural during game-play than moving backwards, as you could still move backwards in the game, but the movement would be so slow that it would not really help you in any situations.

What Genre for VR games In the Next 10 Years?
We are just at the early stages of VR gaming, and when it comes to motion sickness, which is one of the greatest challenge in VR development nowadays, it has more to do with the game being played than the users. I would suggest players to don’t play games that make them sick, but choosing the right games specifically made for VR, with VR consideration in mind. The new generation of HMDs that will be released in the incoming years should also help, being lighter, adding eye tracking that would allow changing the focus real time and thus adding a better feel for distance and depth, being wireless to allow a bit more motion, having better screen quality, etc.
The VR game genre is still being defined, but we can already see the variety in experiences, going from playroom escapades to static space shooters and slow-paced horror shooters, and so for all the reasons mentioned above in this article: VR home entertainment is not made for high-intensity face-paced games, that would by design induce motion sickness and disorientation to their users.
As with every new gaming platforms or device, some new game genres will come out, some old ones will be revived, some new game design rules will be defined, and a monetization scheme will be made and adapted to those genres, or made and adapted to the platforms, which will impact the game genres that will be made for VR.

The most recent example of that is mobile gaming evolution of course. It all started with “Snake” in 1997 on the Nokia 6610, but rapidly, things were to change to sell games for this new platform that were Mobile, as Snake was embedded. It all started with the WAP, which correspond to the time we started to get access to Internet with our phones. And since then, things have continuously evolved on the mobile front, as we now play game as Cash Royal, which could be considered as a game genre that was born because of the mobile gaming platform and monetization possibilities; but we also play games such as Plant Vs Zombie, which could correspond to the logical evolution of casual games like Snake.
The platforms, the market, the type of users, their expectations per experience playing certain type of games, but also their behavior in playing new ones are continuously changing, and that’s what VR developer must face right now. Both game developers and HMDs manufacturers are making efforts, and I am sure we will see new game genre with major trends and specific monetization schemes coming into Virtual Reality. I also think we will see different types of games for different usage, I am thinking specifically of arcade and events or attraction experiences and games, versus home entertainment and mobile VR entertainment, offering all different price accessibility, and different type of games for different usages and different gamers.
players will need to be educated on how to play to new game genre and what to expect from VR games, and that will be by the type of game being accessible on VR platforms, but certainly not by asking them to play games that are not developed with the consideration of motion sickness in mind and just hoping that players will just get used to it with time.

To read the full article visit Gamasutra

Blog: Designing your VR game around motion sickness constraint