For each of the techniques outlined below, we recommend offering controls within the application settings to customize timing and related values for each parameter. People have widely varying reactions to instances of sensory mismatch. One of the easiest ways to improve the user experience is to provide the user control over these key variables, as it allows the user to choose the balance of responsiveness and comfort that work best for them.
Blinks can help improve comfort during teleportation. With this technique, the screen usually fades to black, masking the change in camera perspective. The preferred duration of this effect does vary, so it’s recommended that you give people the option to adjust the timing of the effect.
Snap turns reduce vection during avatar movement by instantly turning the camera a fixed, angular distance. They are also often paired with a “blink” effect (of tunable duration) to reduce - but not eliminate - the disorientation that results from the instant change in perspective.
If there is a blink, or some other transitional effect that takes time to complete, it is important to accumulate additional turn events so that user intent is respected and the camera will orient to the final direction. People should not have to wait for a snap turn’s transition to finish before triggering another turn.
It is important to note that snap turns work by allowing the user to rotate their viewpoint without seeing the associated motion that normally goes with it, thereby preventing vection. However, if the user is able to turn eight or more times within a second, this will trigger motion perception in their brain, and they will experience vection.
Quick turns can reduce the effects of angular vection and disorientation during avatar movement. During quick turns, the avatar turns a fixed angular distance over a very short amount of time, usually 30 or 45 degrees per tap on the controller for under 100 milliseconds. We also recommended that these values can be customized by the user, if needed. Because it happens so quickly, the rotation will be completed before our body has a chance to fully react to the difference between the visual and vestibular signals. Since there is no visual discontinuity, the user’s sense of direction should be well maintained after the turn is completed.
Snap turns and quick turns rotate the user’s viewpoint in discrete increments. While this can improve comfort, it also reduces the precision with which one can reorient their viewpoint, which can potentially lead to frustration. If it is important for the user to orient themselves precisely in your virtual environment, you should provide some means to fine-tune user orientation.
For example, if you know that users will want to adopt a certain position and orientation in the environment, such as to directly face a virtual screen, you could offer them some way of snapping themselves into place. While users might also orient their viewpoint precisely by simply turning their heads, be sure to consider their potentially limited range of motion, and how long they might have to hold such positions.
Many, if not most, people will find simplistic implementations of smooth turning to be uncomfortable. Despite this, it is recommended that you provide a smooth turning option for people who have a strong preference for this control type. There have been many examples of VR applications shipping without smooth turns because of the developer’s desire to provide the most comfortable experience, only to add smooth turning as a result of customer feedback and poor ratings.
We also recommend that you require users to select this mode intentionally to avoid anyone assuming smooth turns (and the potential, associated discomfort) is required to experience your app.
With careful tuning, the smooth turning experience can be improved. For instance, limiting the turn speed to a rate that is reached shortly after the thumbstick is moved will reduce the duration of angular acceleration. For instance, when the thumbstick X value is between 0 and 0.25, the angular velocity will be in the range 0 to 1, and when the thumbstick X value is above 0.25, the angular velocity will be 1.
A position warp effect is experienced when the camera quickly moves to a new position as part of a teleport. It can be helpful for reducing disorientation because it eliminates the visual discontinuity that would happen with an instant teleport. It’s important that this effect is very quick and uses a fixed velocity to minimize the visual and vestibular sensory mismatches. This technique is the same as what is described in Seated Control Issues .
Projected avatars is a technique that enables the user to steer their avatar to a new position in third person. When activated, the camera view in VR remains stationary while the avatar can be seen walking away from the current perspective. Once the movement is complete, the camera perspective shifts over to match the avatar’s final position.
This tactic eliminates vection while moving the avatar because there is no artificial movement of the camera. It can also help reduce post-teleport disorientation because people can view the avatar move to the new position prior to the shift in perspective, and more effectively anticipate what they will see after the camera moves. It also has the added benefit of eliminating the teleport-related discontinuities for other players and NPCs. This can be useful for app designs that would break or be exploited if objects don’t respect physical rules of movement, such as a player trying to evade an NPC. A great example of projected avatars can be seen in From Other Suns, by Gunfire Games.
This technique presents a portal or window to the new location next to the player, showing a portion of the environment from the perspective of the new location. The teleport takes a few moments to complete, and during the transition the portal simply expands around the player, which effectively places them into their new location. This reduces the visual discontinuity associated with other forms of teleportation, since both the current and new location are visible during this process and the visual transition between the two is not instantaneous.
See below for the remaining sections of this guide outlining the many design techniques and best practices to help inspire and inform your next VR locomotion system.