|Required Devices||Motion-tracked controllers|
|Description||Press a trigger on controller to record your origin, lean beyond the boundary threshold to move in game, return to origin to stop|
|Pros||Mitigates VR sickness, frees up the hands while moving, move for longer without being fatigued|
|Cons||Can drift from center of play area, difficult to turn|
The mechanics of Lean-to-Move are simple. The player initiates the movement by pressing the trigger. The system then stores the location of the head when the trigger was pressed as the origin of movement.
Next, the system waits for the player to lean or move outside of the threshold region. Once the player breaches this radius, the distance between the head and the wall of the threshold is used to compute the player’s velocity.
When the player initializes Lean-to-Move, the HMD's original position is saved.
As the player leans away from the origin, the distance from the origin to the HMD is calculated. If the distance is less than the lean threshold, then no movement is created.
As the HMD goes past the lean threshold, the displacement from the lean threshold boundary to the HMD is used as the velocity vector in the game. The further the HMD from the boundary, the faster the player goes. Returning the HMD to the origin brings the player to a full stop.
Lean-to-Move helps to mitigate nausea in a similar way to other locomotion strategies being deployed today. One major advantage of Lean-to-Move is that it frees up the player’s hands to be able to do whatever the game requires. In the FPS setting, for instance, a player can more naturally wield their weapon while moving around. Lean-to-Move also has a low activity overhead, meaning that players can use it for longer without experiencing fatigue.
The best results seem to be obtained when the player keeps one foot stationary while stepping. There is, however, no way to enforce this and even with reminders to the player, it’s easy to forget to do this. Nausea can occur if the footing is not maintained.
This locomotion style also seems to encourage drift from the center of the play space. Eventually the player ends up near the edge of the playspace where they can no longer take a step. This causes a break in immersion as well as frustration.
The simple implementation described above also doesn’t lend itself to easy turning. In order to change direction, the player must return to the origin, reorient their body, and then step in the correct direction. This was the primary cause of players losing their anchored foot. Possible Improvements To address some of the issues above, a number of improvements can be made to the implementation described above. To address the cumbersome change in direction, it may be possible to incorporate the change in rotation of the head into the direction of travel.
To address the variability of the tolerances to nausea, it may be possible to allow players to tune the locomotion parameters to something that feels the most correct. This includes the threshold distance, the max speed, and the gain applied to the lean displacement when calculating the velocity.