XR, MR, AR, VR, and AV: what are extended realities anyway?

Extended, mixed, augmented, and virtual realities (and their respective acronyms) are expressions that circulate when the theme is the production of immersive experiences by synthetic means. What does each one mean? Not knowing the differences and similarities between them generates damage to qualified and technical discussions on the subject.

The practical importance of such technologies, increasingly closer to our daily lives, makes this discussion worth our attention. Therefore, leaving superficiality, I invite you to untie the main terminological knots involved in this theme. Let‘s go?

Terminological confusions in immersive technologies

With the progress of sophistication in the field of immersive technologies, there is an increase in terminology associated with such tools. Among them, the most common are: extended reality, mixed reality, virtual reality, augmented reality, and augmented virtuality. 

Still, given the strong influence of the English language on our vocabulary – which is manifested in several areas of information technology –, these terms are commonly used in English. In a reference to the names punctuated in the previous paragraph, respectively, extended reality (XR), mixed reality (MR), virtual reality (VR), augmented reality (AR), and augmented virtuality (AV) are nomenclatures frequently found in sources on the aforementioned theme, inside and outside the scientific-academic production in Brazil.

During the investigation of the project on extended reality and protection of personal data, we came across a variety in the use of these terms, including a discrepancy in the content attributed by each author to each of them. 

Therefore, in an attempt to “undo the terminological knots” and enable access to qualified discussions on these topics, for people inside and outside the academic environment, I write this brief text. 

Without claiming to exhaust the possibilities included in the question under analysis, the objective here is to clarify the nuances between different concepts, in addition to any similarities between them. 

Thus, it will be possible to reflect, for example, on issues related to privacy and data protection at a later time, in view of the specific characteristics and challenges of each technological tool.

How are the concepts related to extended reality being seen?

First, extended reality (simply and commonly referred to as “XR”) appears to be an “umbrella” term, used frequently to designate the genre that encompasses other specific immersive technologies. In other words, any “reality” with a certain level of synthetic immersion can be considered XR. 

Image source: XR4All

Secondly, virtual reality (VR) is identified as a technology that allows a total user immersion in a totally synthetic environment, without interaction with physical objects. 

This is the proposal of Meta Quest, VR glasses produced and marketed by Meta (formerly Facebook), which isolates the user’s vision and promises to transport him/her to a fantastic reality, entirely created by the company.

Image source: TecMundo

The third point leads us to a slightly more complex investigation: augmented reality (AR), a concept identified with technological resources that mix real scenarios and virtual objects on a single screen, is characterized by the predominance of natural elements. In this way, it is possible to create games, such as Pokémon Go, in which, through a cell phone, it is possible to project a Pokémon on the door of your house, for example.

Image source: Exame

On the other hand, fourthly, augmented virtuality (AV) appears as a similar species since it would also involve the mixture of physical and synthetic realities, differentiating itself by the predominance of virtual elements, unlike augmented reality.

Source: Galileu – O Globo

The fifth and last nomenclature, but no less relevant, is mixed reality (RM). Its definition carries a certain degree of uncertainty, which led Speicher, Hall, and Nebeling to answer the question “What is MR?” with a sincere “it depends”. 

This response generated a scientific article in which six possible notions were identified for the term “mixed reality”, according to a review of sixty-eight papers and an analysis of data extracted from interviews with ten experts in the area, working in academia and commerce. They are, in short:

1. RM according to the “reality-virtuality continuum”: this popular classification comes from the theoretical proposal of Milgram and Kishino, published in 1994, illustrated by a line, which stipulates natural and synthetic reality as two extremes. Between such extreme points, mixed reality is identified as a mixture of real and virtual elements, that is, as a concept that would necessarily encompass the aforementioned augmented reality (AR) and augmented virtuality (AV). According to the original perception proposed by the authors, virtual reality is recognized as the extreme opposite of physical/natural reality; therefore, VR would be outside the mixed reality concept.

Source: article “A Taxonomy of Mixed Reality Visual Displays” written by Paul Milgram and Fumio Kishino.

1. RM as a synonym for AR: indistinct use between the two terms, so that both are identified as technology that mixes real and virtual elements;
2. RM as a type of collaboration for the interaction of AR and VR users: in these cases, RM is referred to as a technology that enables interaction between users of technologies with distinct nature, of AR and VR, which may be, geographically, in different locations;
3. RM as a combination of AR and VR resources: used to refer to systems or applications that combine AR and VR resources on the same device, not necessarily integrated;
4. RM as an alignment between real and virtual environments: it consists of perspectives that associate RM with the virtual representation of a real environment or with the synchronization of physical and synthetic scenarios. This definition differs from n. 3, as there is no reference to a collaboration between users, nor does it usually involve different geographic locations. Likewise, there is a subtle disagreement with the notion in n. 4, because there is no need to combine AR and VR resources here;
5. RM as a more evolved version of AR technologies: RM would be a more immersive, interactive, and improved version of AR resources, due to the advancement of techniques that allow user interaction with virtual elements, as well as between virtual objects and the environment physicist. 

Among so many perspectives and concepts, how to define, after all, what each one is? Furthermore, is delimiting and classifying such technologies really useful?

The (dis)importance of defining the boundaries between the nomenclatures

In the same text mentioned, Speicher, Hall, and Nebeling addressed two related questions: is it useful to establish a single definition for what mixed reality would be — a term with the greatest amount of variations and controversies? Yet, in a forward-looking exercise, is there likely to be distinctions between RM/RV/RA (as well as VA) in the future, or do such technologies tend to be blurred?

The vast majority of people interviewed in that survey stated that a single definition of mixed reality would be helpful. However, the question of the temporality and relativity of the attribution of meaning to each of these terms has been recognized: as direct products of human perception, given the unprecedented character of the development of these sophisticated immersive techniques, it is natural that there will be dissent in the scientific and marketing community.

On the other hand, there is a disagreement regarding the prospection of continuity of distinctions between such technologies. While some defend the tendency towards disuse as the devices improve (and, therefore, can enable access to any of them), others point to the maintenance of the distinction between RM and AR in the face of the completely immersive experience made possible by the RV

In any case, the authors’ position in stating that, at least, it is necessary to previously establish the parameters used for discussions on the subject, especially in scientific studies, seems to be coherent, under penalty of generating technicalities. 

Among differences and similarities, the practical importance of extended reality(s)

The polysemy of specific names for immersive technologies — in particular,  XR, RM, RA, VA, and RV — is a fact with no expected expiration date. On the other hand, it is undeniable that they are already used in different ways and promise to increasingly impact our daily lives, as in the case of the infamous Metaverse. Thus, promoting studies and discussions about the extended reality(ies) is imperative.

In investigations on issues related to the theme, for constructive and qualified communication, it is, therefore, necessary to define the conceptual parameters adopted for each one of them.

With the growth of research in the field, knowing what is previously understood about each nomenclature makes possible a detailed analysis of the paradigmatic changes promoted by the extended reality, which occurs, for example, in the regulatory parameters of the protection of personal data, as a result of the unprecedented collection of extremely sensitive data, such as biometrics.To learn more about the topic and its practical implications for our privacy, I invite you to know the other texts in the series of articles produced by our team, as well as to follow and interact with the Institute of Reference on Internet and Society (IRIS) on its website and social media.