One of the most commonly cited concerns about VR is that it will make people sick. It used to be a technology issue, displays and computers simply couldn’t output moving images at a rate necessary for comfortable virtual reality. Today we have largely conquered motion sickness on a hardware side with faster processors and screens that refresh 90 times a second or more. That said, if you move the player in the game the wrong way, you’re probably going to make them sick.

Christopher Parkin is the co-founder of Offpeak Games, the Aussie indie studio behind Valiant, a medieval first person combat game built for VR. Their game is based on the ability to move comfortably throughout the game. Parkin offered to share some of Offpeak’s methods reducing sickness with VR locomotion with us.

1. Reduce non-forward movements

Movements that are unlike the ones we make in real life tend to cause simulator sickness. These would be movements that conflict with what our brain is expecting, things like moving forward while looking to the side. There are some ways to prevent this, such as only allowing movement in the direction the user is facing, but they are limiting for gameplay.

2. Reduce Vection

Imagine you’re on a train and look out the window to see a train leaving the station. As that train begins to move it creates an illusion of movement in your own mind and your brain’s likely conclusion is that the train you are on is actually moving in the opposite direction, that illusion is called “Vection.” Vection occurs when a portion of what you can see moves, and is one of the things that can lead to motion sickness in VR.

Read More: Introducing Limbo, a VR camera movement technique by the developers of Colosse

You can reduce vection with a number of different techniques, such as reducing the complexity of the textures and reducing the speed of player motion.

3. Reduce Accelerations

Our inner ear detects various changes in velocity, or accelerations, but it doesn’t detect constant velocity. Because of this, developers can have someone moving at a constant speed in a relatively straight line and the simulator sickness effects will be greatly reduced.

However, when you begin adding lots of ‘elliptical movements’ (i.e. turns and jumps) and changes to the velocity it adds a lot more potential to make people sick. That is one of the reasons that roller coaster demos tend to not be the best way to introduce people to VR

4. Reduce camera YAW

YAW refers to movement along a vertical axis, such as turning the nose of an aircraft. YAW is also one of the quickest ways to get someone sick in VR. When you connect a game’s YAW control to a stick, rather than to your head motion, it creates an uncomfortable disconnect that Oculus’ CTO John Carmack has gone as far as to call “VR poison.” Stick controlled YAW is something that developers should avoid as a hard and fast rule.

This can lead to design constraint in games because it requires the player to be either in a swivel chair or standing for the experience. When you add cords to the mix it makes things even more messy. Using things like a ‘comfort turning’ mode, a mode that jumps the user X number of degrees either direction instantly, can help one comfortably turn along the horizontal axis, but they come at the expense of immersion.

5. Add a static reference frame

It may not be a perfect fit for every game or experience, but adding some form of reference around the player can greatly reduce simulation sickness, and possibly help increase immersion. For example, adding a cockpit around the player in a high speed space fighter, like EVE: Valkyrie gives a player a point of reference that helps the player ground themselves to the motion around them. It can also come with the added benefit of increasing immersion in some cases. The video above cites a connection between the weight of the headset and the weight of a virtual helmet as being a touch point for immersion, as many users associate the two.

The rules of motion in virtual reality are still being fully determined. Many of the earliest consumer VR experiences will air on the side of caution when it comes to comfort but speaking with a number of developers, some are choosing to throw caution to the wind and experiment further. One of the reasons for this is a concept I have taken to colloquially call your ‘VR Sea Legs.’

When a land-lubber steps onto a boat for the first time, often the rocking and variations in vestibular motion from the ocean causes a feeling of ‘sea-sickness’ that is not too different from simulator sickness. However, for most people, after a few hours or days that feeling typically dissipates as they get what is commonly referred to as their ‘sea legs.’ It is something that experienced seamen are very well adapted to. It is also something, I would argue, that replicates itself in VR.

The more time one spends in VR stressing the rules of comfort, the more one becomes acclimated to it. It is something that I have personally experienced and many others have pointed to as well. Eventually I believe the rules around comfort will begin to evolve and loosen up as more people get their ‘VR Sea Legs.’ When that happens, I think we will see an influx of creative techniques surrounding motion, and it will be interesting to see how those rules evolve over time; but until we get there, it’s best to focus on making sure people don’t get sick in the first place.