In many VR experiences, users want to move well outside of the matched zone. This motivates locomotion, which means moving oneself in the virtual world, while this motion is not matched in the real world. Imagine you want to explore a virtual city while remaining seated in the real world. How should this be achieved? You could pull up a map and point to where you want to go, with a quick teleportation operation sending you to the destination. A popular option is to move oneself in the virtual world by operating a game controller, mouse, or keyboard. By pressing buttons or moving knobs, your self in the virtual world could be walking, running, jumping, swimming, flying, and so on. You could also climb aboard a vehicle in the virtual world and operate its controls to move yourself. These operations are certainly convenient, but often lead to sickness because of a mismatch between your balance and visual senses. See Sections 2.3, 10.2, and 12.3.
Steven M LaValle 2019-03-14