Motion sickness is one of the most common negative side-effects of VR experiences. This can include a feeling of seasickness, headaches, general nausea, dizziness, vertigo or even in some cases, vomiting. This happens when there is a mismatch between what is being seen and what is being felt — or in other words, your eyes see that you’re moving, but your body doesn’t feel any motion.
It is very important to take this problem seriously and ensure that the experiences we create have precautions in place to reduce the possibility or risk of sickness.
TL;DR list of do’s and don’ts
Do
- Keep the user grounded.
- Give users control over movement.
- Use constant velocity.
- Use care with acceleration and deceleration.
- Maintain head tracking.
- Warn the user if something might cause disorientation or discomfort.
Don’t
- Don’t shake or move the horizon.
- Don’t use rapid movements or abrupt transitions.
- Don’t suddenly change the direction the user is facing — especially when in motion.
- Don’t turn the camera for the user. Instead, let them turn their head to change their view.
- Don’t throw the user into an experience that is known to cause discomfort without warning them.
- Don’t artificially delay the user’s motion. If the user starts to move, make sure the environment responds immediately and in real time.
Speed and control of movement
Start with slow and smooth motion and gradually increase the speed steadily.
Let the user initiate and control the movement. This is similar to how a driver has less chance of becoming car sick than a passenger since the driver is able to anticipate what’s about to happen.
Slow speeds for virtual locomotion are less uncomfortable than normal human speeds. Human speeds are 1.4m/s for walking and 3m/s for a light jog. Try slower speeds than this to decrease chances of nausea.
Grounded objects
Explore ways to cause objects to move while keeping the horizon steady and the user grounded. If you don’t have a grounded point of reference, the reaction is similar to how people are more likely to get seasick when they’re further out to sea and can’t see land. You get a little better when you go out on deck and stare out at the stable horizon, but not as much as when there’s land in sight.
If a user is sitting in a chair in the real world, consider sitting them on something in the virtual world such as a virtual cockpit, chair, or other stationary element. This helps reconcile the differences in motion and reduces the chances of nausea.
If a very large virtual object is moving, the user can get disoriented and think they’re moving. Much like a car sitting at a railroad crossing, after a certain amount of time the driver feels like they’re moving sideways instead of the train. You can avoid this by placing smaller fixed objects within the space — like the railroad crossing signs and arms, and the foundation supporting them.
Head tracking
Even a short pause in head tracking can cause illness such as a sense of vertigo. Test the application closely for unintentional latency or freezes in performance.
If the app drops head tracking consistently at a particular time, fade the screen to black before losing tracking if the issue can’t be resolved. If you must fade to black, continue playing audio so that the user doesn’t think the application froze or crashed on them. Regardless, this is a very high priority issue to resolve as soon as possible.
Examples to try at home (if you dare)…
Comfortable experience
Richie’s Plank Experience
There is a small amount of discomfort, but it’s very minimal. It is reduced with good utilization of gradual acceleration. This can still be a problem for people highly sensitive to motion. At first when falling, I do get the feeling of my stomach dropping, but it goes away almost immediately. Overall, a very good introduction to handling motion in VR.
Uncomfortable experience
Roller Coasters — of any kind
These experiences break all the rules. And yet for some reason, these are always some of the first experiences people run to when trying VR. Unless puking is your thing, just don’t do it. Here’s a video instead.
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I’m an Immersive Tech UX Design Professional with over 22 years of experience designing for kiosks, websites, mobile apps and desktop software for many well-known and not-so-well-known companies.
I’m not speaking on behalf of or representing any company. These are my personal thoughts, experiences and opinions.
