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TopDefining Technology Enhanced Realities: Virtual, Mixed And Augmented
Milgram et al. (1994) provide a helpful representation of how reality and virtuality are connected (see Figure 1). This shows a continuum encompassing all real and virtual objects and environments. Mixed reality is an area in the middle, where the two extremes meet, and is considered a blend of the virtual and the real.
Figure 1. Representation of the reality-virtuality (RV) continuum, re-drawn from Milgram et al., 1994
Azuma (1997) defined AR as “3-D virtual objects […] integrated into a 3-D real environment in real time”, reflecting early research into the use of AR as a primarily graphical display. We consider this definition too narrow and prefer a working definition of AR that includes the fusion of any digital information with physical world settings, i.e. being able to augment one’s immediate surroundings with electronic data or information, in a variety of formats including visual/graphic media, text, audio, video and haptic overlays. Indeed, in a later paper, Azuma et al. (2001) updated his definition, reducing the emphasis on graphical objects and identifying the three essential properties of AR as: the combination of virtual and real objects in a real environment; a system that aligns/registers virtual and real objects with each other; and that runs interactively in real time. Their paper also defines ‘mediated reality’ or ‘diminished reality’, where some real objects are electronically stripped out, so users are better able to focus on other aspects of their environment.
A critical aspect of AR is the dialogue between the media and the context in which it is used, i.e. how the media responds to and changes that context. It is not enough to state that AR consists of availability or presence of digital media within a particular location, as this could encompass passers-by playing music on their mp3 players as they travel through that environment. Rather, we need to take into account the explicit intention of the digital media deployment, to supplement or augment our surroundings through additional information being made available (e.g. visually, auditory or through haptic interfaces) that has contextual relevance to that specific place.