This section evaluates how effective and precise are the mechanics focused on getting the user around and going through the experience. It is about the way a user embarks onto navigating the virtual world.
The viewport is the virtual perspective or "window on the (virtual) world" from inside the headset, and locomotion systems take the headset from one coordinate point to the next one.
For a deep dive on locomotion in VR, see this video from Valve about Half-Life: Alyx.
How to answer "How many means of locomotion exist?"
Whether they are available all the time or occur individually at different stages of the application, select the total number of locomotion types provided by the experience (the user may teleport around, climb, run, takes a rollercoaster ride and use a zipline at different stages of the experience; all would be considered one different mean of locomotion).
Echo Arena (Ready at Dawn, 2017)
Unrestricted 3 degrees of freedom are systems that allow swimming underwater, flying freely, or using rocket thrust to move in a Zero-G environment (move up, down, back, forth, left or right willingly)
HTC Home (Valve)
2 degrees of freedom describes mechanics like teleporting or walking, where the raycast must point to a position on a plane (or one moves through a surface), whether one teleports to a wall or a floor, there is only X and Z, Y and Z or X and Y to select the next location. (Climbing also occurs on 2 degrees of freedom as one grabs from a surface to move)
One degree of freedom occurs when the user can only decide to continue on through a predetermined route or actually cannot decide at all when to move (like a roller coaster; in this case, a ride on a boat through a canal)
placeholder for image
Full gait refers to the tracked movement a 6DoF system naturally has; it allows users to look around, kneel down, and walk in their "Guardian" or "Room Scale".
Select this option primarily if the navigation system encourages the player to lurk a lot around by moving in the game area.
RIPmotion (Ryan Sullivan, 2016)
Partial gait occurs when the user simulates walking by lifting the legs as in giving steps; head or controller orientation usually provide a direction and the legs bounciness captures enough data to start moving the camera around.
Cosmic Wandering (Punchey, 2016)
Scaled gait or redirected walking occurs in many ways. A scaled gait may take one step forward as walking 10 meters in the virtual world. Redirected walking is a system where the user may walk around the content area but the camera orientation starts to adapt to the limits of the content area, redirecting the camera itself through virtual rotation or by having the user rotate in the content area without rotating the camera's orientation in the virtual world. In this example, the user holds a button to lock the camera's orientation while rotating their body for more room space and releases the button when redirected.
Dreams of Dali (Goodby, Silverstein & Partners, Half Full Nelson, 2018)
Explicit teleportation occurs as a predefined route for all users to experience exactly the same points of view. They are limited, defined points that the user can teleport to.
Implicit teleportation provides the user with multiple destination points on a terrain for selecting teleport locations.
User is teleported to the selected point instantaneously, like a cinematic jump cut.
User is teleported to the selected point during a subtle fade down and fade up, like a cinematic jump cut.
Movement will speed the user forward to a selected point, usually with blurred or darkened outer edges using a “vignette” effect.
Uninterrupted movement often using input device or joystick, where the user perspective or camera glides forward in the indicated direction. The camera may be stabilized or imitate walking with undulating motion with accompanying stepping audio effects.
VR Walking Prototype (David Dewhirst, 20xx)
Whether using tracked hands or the input device's tracked movement, gestures simulate movement through patterns. This GIF shows the swinging gesture that simulates walking by moving the arms.
World in miniature (similar to Voodoo Doll) uses a miniature-scaled prop for changes in the scaled environment to occur. In this GIF, the player may move from the bricks room to the yellow room by using the "worlds in miniature".
Tilt Brush (Google, 2016)
Scaling the World is commonly used by design apps like Tilt Brush, Medium by Adobe, Google Blocks when moving the viewport around and "zooming" in and out of the 3D Artwork in progress. It usually occurs by holding both triggers (in Oculus the user usually holds both grip buttons) and moving both hands apart scales the world bigger while bringing the hands together "zooms out" or makes the world smaller; moving the hands parallel in a direction keeps the same scale for the player but allows for a camera replacement, which is a very useful locomotion technique when finding the right angle to tweak the user's artwork.
Multiple Cameras allows the player to jump back and forth between various camera locations to decide where the user wants to look from.
Vignette Effect is a reduced Field of View (sometimes accompanied by a squared plane like in Google Earth VR) allowing for rapid and abrupt movement while lowering the chances of Motion Sickness. This works because the peripheral vision is blocked and the center field of view gives room for focused navigation.
Citation:
Joseph J. LaViola, Doug A. Bowman, Ernst Kruijff, Ivan Poupyrev; 3D User Interfaces Theory and Practice. Addison-Wesley Professional; 2nd edition (2017).
Jason Jerald. Ph.D.; The VR Book: Human-Centered Design for Virtual Reality. Assocation for Computing Machinery and Morgan & Claypool Publishers (2016).