Since AR evolved from and shared partial
commonalities with VR because of their computer-generated
elements, in 1994, Milgram and Kishino presented the
concept of a virtuality continuum, as shown in Fig. 1,
defining environments consisting solely of physical objects
(e.g., a video display of a real-world scene) on the left, and
environments consisting solely of virtual objects (e.g., a
computer graphic simulation) on the right. Described as the
possibilities of the mixture of real-world and virtual-world
objects within a single display, mixed reality exists at any
point on this continuum and encompasses both augmented
reality and augmented virtuality (Fig. 1).