An omnidirectional treadmill (ODT) is a machine that allows the user to travel in any direction. In contrast, conventional treadmills constrain the user to linear movement: forwards and (sometimes) backward. Depending on the particular product, an ODT may or may not enable other types of locomotion, such as crawling, and different postures, such as sitting, kneeling and crouching.
Like conventional treadmills, the omnidirectional version can facilitate fitness or physiotherapy but the most common application is for locomotion in VR gaming, where the systems work in conjunction with VR headsets. The machines help give users the impression that they can move freely in a virtual or mixed reality environment, a capacity that is essential for a fully immersive experience.
Most omnidirectional treadmills tether the user on a platform that moves to conform to the user's direction of locomotion, keeping them within a restricted area while affording the perception of free movement. Most keep the user physically confined to a small area; others enable a greater range and use sensing technologies to detect when the user moves away from the center of the machine. That type of ODT also requires mechanisms to continually move the user back to the center without making that movement apparent and thus calling attention to the artificiality of the environment.
Watch a demonstration of Infinideck, an ODT featured in the movie Player One: