Definitions and characteristics of AR

One of the earliest formal definitions of AR was proposed by Azuma (1997). It identified three characterizing elements of AR technologies: the combination of real and virtual elements, real-time interaction, and the reproduction of content/elements in 3D. Building on Azuma's definition of AR and its three elements, several other authors have provided their definitions of AR (Table 12). These definitions emphasize the technical and user experience aspects of AR, and they convey that the natural environment is the main feature of AR, combined with sensory digital/virtual contents.

Table 12. Definitions of AR and prevalent elements (Caboni and Hagberg, 2019)

The most applied and accepted definition of AR (Azuma et al., 2001) is that AR is the conjunction of real and virtual imagery with real-time interaction and 3D registration. This definition states that technology adds to the real-world image with layers of digital information (Cipresso et al., 2018). The overlaid sensory information may be constructive (i.e., additive to the natural environment), or it might be destructive (i.e., masking of the natural environment) such that it is perceived as an immersive aspect of the real environment via visual, olfactory, or tactile means. The logic of interaction between humans and the system is designed based on the three interaction modes of sight, gesture, and voice.

AR comes in different display types and can work in various settings (Appendix 4 details the technology components of AR and types of AR). It comprises three foundational design components: (a) a tracking method that connects virtual and real worlds, (b) a projection device that transforms data to visual stimuli, and (c) a data feed that provisions data to process and display.

Authors Definition of AR Prevalent elements

Carmignani and Furht (2011) AR is defined as a real-time direct or indirect view of a physical environment that has been augmented by adding virtual computer-generated information

Real time

Physical environment Virtual information Sood (2012) AR converges the physical world with virtual objects, augmenting the view of the

physical world with streams of information from the Web

Physical world Virtual objects Ukwuani and Bashir (2017) AR is aimed at improving and enhancing the way we perceive our surroundings by

combining technologies such as computing, sensing and display technologies

Enhanced surroundings Combined technology

Olsson et al. (2013)

AR is a technique that combines real and computer-generated digital information into the user’s view of the physical real world in such a way that they appear as one environment

Combination of real and digital information

Physical world Real world Scholz and Smith (2016) AR seems to be an ideal technology for forging deeper relationships, as it fuses and

entangles branded content with consumers’ own environments and bodies

Ideal technology Forging relationships

Javornik (2016a, b)

AR is an interactive technology that modifies physical surroundings with

superimposed virtual elements. The user can add textual information, images, videos or other virtual items to the person’s viewing of the physical environment

Interactive technology Physical surroundings Virtual elements Grewal et al. (2017) AR is one of the emerging applications that will define the future of retailing Emerging application

Future of retailing

Hwangbo et al. (2017)

AR refers to the computer graphic technology that visualizes things that exist in the natural environment by combining computer-generated sensory inputs such as sound, video, graphics, or GPS data from the physical, real world environment

Computer graphic technology Natural environment Sensory input

Pantano et al. (2017) AR is a real-time view of the physical world augmented with virtual computer-generated information

Real time view of the physical world

Virtual information Poushneh and

Vasquez-Parraga (2017)

AR is a series of technologies that integrate real world and virtual information, enhancing a specific reality

Real world Virtual information Rese et al. (2017) AR integrates computer-generated objects with the real environment and allows

real-time interactions

Real environment Real time interactions Yim et al. (2017) AR is defined as the superposition of virtual objects on the real environment of the

user

Virtual objects Real environment Brengman et al. (2018) AR allows for the digital overlay of content to the user’s real environment Digital content

Real environment Lee and Leonas (2018) It brings virtual and artificial objects into a real environment Virtual and artificial objects

Real environment Poushneh (2018) AR is an interactive technology that generates three-dimensional virtual content and

then maps it onto the user’s reality

Interactive technology Virtual content

Watson et al. (2018)

AR layers virtual elements over physical environments, and blends virtual worlds with reality. AR is a system to have these properties: combines real and virtual objects in a real environment; runs interactively and in real time; registers (aligns) real and virtual objects with each other

Virtual elements Physical environment Interactivity Real time

Technically, tracking registration technology is generally considered the critical design component of AR and is the main limitation to applying current AR solutions (Harrington et al., 2019). The registration task is to determine the mapping relationship of virtual objects in different coordinate spaces and display them in the image's correct position, in real-time, to achieve AR. The performance of registration positioning directly determines the success of the AR solution. Three-dimensional tracking registration can be divided into three categories: sensor-based tracking registration technology, vision-based tracking registration technology, and hybrid tracking registration technology (Machado and Vilela, 2020).

The tracking method deploys virtual images over real-world objects via one of these approaches:

• SLAM: Simultaneous Localization and Mapping (SLAM) localizes sensors to their surroundings, while at the same time mapping the structure of the environment.

• Marker: The marker-based method (also known as the Recognition method) uses a camera to identify visual markers or objects. Marker-based AR technology depends upon a device camera to distinguish a marker from other real-world objects.

• Location: The location-based method (also known as the markerless method) uses GPS, digital compass, velocity meter, or accelerometer to provide location data. The location detection features in smartphones enable leveraging this type of AR, making it quite popular.

The projection of data to visual stimuli typically uses one of these presentation devices:

• Smartphones: On smartphone devices and tablets, AR can be rendered either through location services, camera, or a combination of both (Butchart, 2011). The viewer can see the modified input from the camera on their screen.

• Large displays: PCs and connected TVs support relaying virtual objects over a webcam (Azuma, 1997). Since it is a hectic process to manipulate a tracker in front of a screen, there are not many AR applications on PCs or smart TVs.

• Smart glasses: Head-mounted displays, glasses, and lenses make AR an integral part of the entire field-of-view. It gives a more life-like AR experience, offering a broader scope of applications (Rauschnabel and Ro, 2016).

The data provision in AR brings data to overlay visuals in a three-dimensional space. Two primary forms include static and dynamic data provisioning.

• Static data provisioning: Augmented Reality technology brings life into static content. By looking through a handheld or head-mounted device, users can view virtual content superimposed onto static scenes and interact with the virtual content using various channels such as gesture or/and voice.

• Dynamic data provisioning: Dynamic data provisioning refers to the pace at which both structured and unstructured data is refreshed and the format in which it is available. These must support the need to make decisions while providing a customer experience that can understand the user's information.

Three characteristics that define AR technology are:

• Vividness or quality of augmentation - task completion and user feelings strengthened by the realism and quality of the medium's images.

• Interactivity - users expect to be able to interact with a device easily, and

• Informativeness - reducing uncertainty in the decision-making process where customers want and expect to find useful information in an easy and fast manner to support their actions and decisions.

Several authors have pointed their attention towards these characteristics (Huang and Liao, 2015;

Pantano, Rese, et al., 2017; Rese et al., 2017; Rese et al., 2014; Yim et al., 2017). They can be considered essential measurement tools to explore AR's possible impact on customers and their interactions with this technology (Pantano, Rese, et al., 2017).

Augmented Reality versus Virtual Reality

The use of AR is based on the reproduction of 3D images of virtual objects. It is similar to VR, but it is essential to underline their main differences. AR is principally characterized by the superposition of virtual elements generated by a computer on users' real and physical environment (Cho and Schwarz, 2010; Drascic and Milgram, 1996). Even if AR's purposes and VR are similar, they address these aims in different ways. AR consists of reproducing virtual objects in the real environment, while in VR, the reproduction of the object is developed by devices that users have to wear (Milgram et al., 1994). More specifically, VR is defined as a realistic 3D environment produced by a computer (Burdea and Coiffet, 2003) and composed only of virtual elements (Milgram et al., 1994). VR obscures the actual reality, whereas AR enhances the actual view (Peddie, 2017). In AR, the user is still aware of the surroundings because they can still see the real world (Hsieh and Lee, 2015).

There is some overlap between hardware devices for AR and VR. A smartphone device can be used in either an AR or VR implementation, depending on the smartphone application. An AR experience will use the phone's camera, while a VR experience limits the user's vision to only the phone display. While VR is generally characterized by three degrees of freedom (3DOF), AR provides additional visual information augmented on the physical world with six-degrees of freedom (6DOF). 6DOF entails that

the camera is positioned and oriented in three-dimensional space (i.e., forward/backward, up/down and left/right) in combination with changes in orientation (i.e., pitch, yaw, and roll) (ibid.).

Considering the differences between AR and VR, AR's positive effects are more appropriate for consumers. Through AR, for example, consumers have the opportunity to test several products/clothes without physically trying them (Verhagen et al., 2014; Yim et al., 2017). Porter and Heppelmann (2017) and Javornik (2016) suggest that only a limited number of retailers will adopt VR because its

implementation is costly and time-consuming compared to AR. Besides, consumers seem to be reluctant to immerse themselves fully in a virtual world and prefer a setting in the real world with which they are familiar and comfortable (Bonetti, Warnaby and Quinn, 2018).