The quest to establish a smooth, intuitive and unobtrusive interface between computer generated worlds and their human visitors has spawned a variety of unusual devices. Head mounted displays consist of small computer monitors built into goggles. The purpose of these HMD's is to fill an operator's entire field of vision with the vista of a virtual world and thereby create the illusion of being within that world. Head trackers are input devices that tell the computer the direction in which the operator is looking. More exotic systems use treadmills, stationary bicycles, electronic body suits and myriad other devices to allow operators to navigate virtual worlds.
Virtual reality is a relatively new phenomenon.
Although the theoretical basis of interactive computer interfaces was discussed by pioneers such as Ivan Sutherland at the University of Utah as early as the mid 1960s, practical models did not follow until the mid 1970s. In the 1980s public awareness grew as practical applications were found for virtual reality. Today, elements of VR can be seen in interactive computer games such as those found in arcades, home computers, and entertainment systems. At Disneyland and Disneyworld, patrons can enjoy computer controlled rides that create the illusion of hurtling through outer-space or through the human body. Commercial airlines and the military use computer based flight simulators to train pilots as well as airport simulators to train air-traffic controllers.