In my previous post, I explored the many definitions of augmented reality and what it means to persons with different perspectives. In this post I have set out to couch augmented reality in the context of other related concepts in order to further define the space where it exists and better understand the distinction between AR and these related terms.

Virtual Reality
Virtual reality (VR) is a good place to start because it is often confused with AR or assumed to be the same thing. There is an oft cited paper by a researcher named Paul Milgram whose 1994 paper “A Taxonomy of Mixed Reality Visual Displays” I borrow from extensively for this post. According to Milgram, “The conventionally held view of a VR environment is one in which the participant observer is totally immersed in, and able to interact with, a completely synthetic world. Such a world may mimic the properties of some real-world environments, either existing or fictional; however, it can also exceed the bounds of physical reality by creating a world in which the physical laws ordinarily governing space, time, mechanics, material properties, etc. no longer hold.”  This is in contrast to AR which is a view upon the real world rather than an entirely synthetic one. VR has received a great deal of press lately because of Facebook’s $2 billion acquisition of Oculus Rift who developed a new mobile virtual reality headset for gaming that purportedly provides an outstanding experience.

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Credit: Futurelab

Mixed Reality
According to Milgram, mixed reality refers to the merging of real and virtual worlds to produce new environments and visualizations where physical and digital objects co-exist and interact in real time. To convey the distinctions, he plots VR at one end of a continuum and a view of reality itself at the other. Every technology in between can be considered a form of mixed reality, of which augmented reality is one form.

Reality
Of course any discussion of alternative realities should also include a definition of reality itself in this context. Milgram states that real environments consist solely of real objects and includes what is observed through some sort of window unto the world such as a video display. Real objects have an objective presence in the physical location being viewed.

Mediated Reality
Mediated reality (MR) is a term posited by wearable computing pioneer Steve Mann that refers to the artificial modification of human perception by way of electronic devices that alter sensory input. Whereas augmented reality adds to or overlays reality, MR also encompasses obscuring, removing, replacing, enhancing or otherwise modifying visual reality. So according to Mann, AR would be one form of MR.

Diminished Reality
Diminished reality (DR) is a form of Steve Mann’s mediated reality that describes technology that can remove, at will, certain undesired aspects of regular reality. With DR, distracting or non-task oriented information is removed from a video feed in real time. For example, a mechanic using a heads-up display to perform a complex repair on a jet engine may see only the components he is operating on while all other parts are blacked out.

Credit: Technische Universitat Ilmenau

Augmediated Reality
As described by Steve Mann, augmediated reality refers specifically to the use of diminished reality in concert with augmented reality to address the problem of information overload that AR can bring. To extend the above diminished reality example, if the mechanic had information and/or graphics superimposed on his (diminished) view of the jet engine this would be augmediated reality. Mann maintains that this is more effective then augmented or diminished reality alone.

Augmented Virtuality
Augmented virtuality is the inverse of augmented reality in that it refers to a view of a virtual world in which real objects are dynamically integrated into, and can interact with the virtual world in real-time. An example of this would be branded product placement in a massively multiplayer online role-playing game (MMORPG). A player can purchase a can of coke to quench their character’s thirst and that can is an image of an actual coke can (rather than an animated rendering) that the character raises to it’s mouth and drinks from. Augmented virtuality lies on Milgram’s mixed reality continuum.

Credit: Westfalische Wilhelms-Universitat Munster

Non-visual AR
Sensual stimuli can be integrated into augmented reality experiences to enhance them beyond the visual realm. According to a study by Huong Q. Dinh, et al., “… increasing the modalities of sensory input in a virtual environment can increase both the sense of presence and memory for objects in the environment.” Consider a hypothetical example of an multi-mode AR experience for visitors to a western national park to see what it was like when bison stampeded across the prairie. In addition to the optical display (i.e. AR glasses) that would project images of bison on the real prairie around the visitor, there would be the following additional stimuli: Stereo headset to surround the visitor with hoof and grunt sounds that spatially correspond to the visual images of the beasts (auditory stimuli). Air blasters that blow on the visitor as the virtual stampeding bison pass close to them (haptic stimuli). Vibrating plates under the ground to simulate the mass of the animals shaking the ground as they stampede by (motion stimuli). Vents that emit artificial bison odor (olfactory stimuli).

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