Virtual Reality Experience

The concept of VR experience is based on the human perception of the extent to which people feel a sense of “being there” in a virtual world (Slater & Usoh, 1995). There are two main factors characterising the VR experience from the psychological and physical points of view, which are Sense of Presence (SoP) and Immersion (Mario et al., 2008).

2.2.2.1 The Sense of Presence

VR experience is often explained by the sensation of “being there”. The feeling of being in the VR is also called the Sense of Presence. The SoP is discussed in various literatures related to VR with reference to Slater and Wilbur’s def- inition: “Presence is a state of consciousness, the sense of being in the virtual environment” (Slater & Wilbur, 1997). There are several definitions and theories to describe the notion of SoP from different points of view.

The Theory of Presence

In media and emergent technologies, the sense of presence is generally defined as the perceptual illusion of non-mediation (Lombard & Ditton, 1997). An illusion of non-mediation occurs when the users fail to recognise the existence of a medium in their communication environment and react as they would if the medium were not there (Lombard & Ditton, 1997). Lombard and Ditton proposed six different conceptualisations to explain the sense of presence, as follows:

X Social richness - The degree in which a medium can be perceived as social, warm, or personal.

X Realism - The degree in which a medium can accurately produce objects, events and people

X Transportation - The degree in which a medium can transport a user to another place.

X Immersion - The degree in which a medium can engage a user to the me- diated environment.

X Social actor within medium - The degree in which a medium can be socially responded to a representation of a person through a medium.

X Medium as social actor - The degree in which a medium can be perceived as a social actor.

Focusing on the SoP in virtual environments (VEs), Slater and Wilbur (1997) proposed the difference between presence (human responses to the system) and immersion (physical reality) in VEs. Presence is a subjective phenomenon, such as the sensation of being in VEs, and immersion is an objective description of

aspects of the system, such as field of view and display resolution (Slater & Wilbur, 1997). Furthermore, IJsselsteijn et al. (2000) argued that the SoP in VEs can be distinguished from social presence (the feeling of being there) and physical presence (the feeling of being physically located in a place). According to their definitions, the SoP can be described as the experience of being in VEs rather than the actual physical surroundings.

Heeter (1992) suggested the dimensions of presence, proposing three different types: Personal Presence, Social Presence, and Environmental Presence. Per- sonal presence describes a measure of the extent to which an individual believes in being in the VEs. Social presence is the extent to which multiple individuals believe in being in the VEs. Environmental presence explains the extent to which the environment itself acknowledges and reacts to the individual in the VEs. From a different point of view, Schloerb (1995) characterised the SoP by two different types of presence in VEs: Subjective Presence andObjective Presence. Subjective presence is defined as the possibility that the individual evaluates himself to be physically present in the remote or virtual environment. Objective presence is produced by the possibility of successfully achieving a task.

Furthermore, Zeltzer’s taxonomy of VEs has often been cited to explain the notion of SoP as a method of evaluation for VEs (Zeltzer, 1992). He proposed that VEs can be characterised by three main components: Autonomy (the extent to which the VE is more than just passive geometry), Interaction (the degree to which VE parameters can be modified at runtime), and Presence (the measure for the number and fidelity of available sensory input and output channels). The correlation between the three components can be drawn as a cube (Figure 2.4).

Figure 2.4: AIP Cube (Zeltzer, 1992)

The Cause of Presence

Most researchers have verified that the SoP is interrelated to perceptual and psychological aspects. Schuemie et al. (2001) summarised previous research and their findings about the aspects of the cause of presence in VEs. Table 2.2 below reproduces this summary of the presence-provoking factors, adding several studies that were absent from Schuemie et al.’s analysis.

Authors Factors

Slater & Usoh (1995) XHigh-quality, high-resolution information XReliability across all displays XInteraction with environment XEffect of predictable actions

Slateret al. (1995) XDynamic shadows

Witmer & Singer (1998) XControl factors XSensory factors XDistraction factors XRealism factors

Sheridan (1992) XExtent of sensory information XControl of relation of sensors to environment XAbility to modify physical en- vironment

Steuer (2003) XVividness XInteractivityXUser characteristics Lombard & Ditton

(1997)

XThe content of the informationXUser characteristics Welchet al. (1996) XPictorial realism of a virtual environmentXVisual feed-

backXObserver interactivity

Wilsonet al. (1997) XVisual depth cuesXCyber-sickness Sadowski & Stanney

(2002)

XEase of interaction XUser-initiated control XPictorial realism XLength of exposure XSocial factors XInternal factors:individual differenceXSystem factors: system de- sign

Barfield & Weghorst (1993)

XDisplay technology XImmersion XSensory fidelity XAttentional resource

Heeter (1992) XUser’s personality XMovement and navigation XFeedback

Table 2.2: The Factors of the Cause of Presence 2.2.2.2 Immersion

The concept of immersion is strongly related to the technology that allows users to experience a continuous stream of stimuli by the interaction with multimodal sensory inputs (Draper et al., 1998; Witmer & Singer, 1998;Slater & Wilbur, 1997; Ellis, 1991). For example, Ellis (1991) defines immersion as “consisting of content, geometry and dynamics, with an egocentric frame of reference, including perception of objects in depth, and giving rise to the normal ocular, auditory, vestibular, and other sensory cues and consequences.” In addition, Slater and Wilbur (1997) describe the concept of immersion as “the extent to which computer displays are capable of delivering an inclusive, extensive, surrounding, and vivid illusion of reality to the sense of the VEs participant.” These definitions indicate

that the concept of immersion is a physical configuration of the user interfaces in a VR system rather than a psychological characterisation of what the system supplies to the human participant.

Immersive virtual reality is often classified into fully immersive (head-mounted displays), semi-immersive (large projection screens), and non-immersive (desktop- based VR) (Kalawsky, 1996). This classification depends on how much the indi- vidual can perceive the VEs as a real world. Figure 2.5 shows VR displays and their immersive levels.

Figure 2.5: Immersive VR Systems (Kalawsky, 1996)

The typical fully immersive system is a head-mounted display (HMD). The HMD has a stereoscopic display (two small displays) and speakers in a helmet, as well as a sensor for head movement tracking. The displays deliver slightly different images to each eye, and users perceive depth and dimension. The head tracking sensor allows the user’s view of the virtual world to change in correspondence with

the head movements made in the real world. These combinations of technology create a sense of inclusion within a virtual world, and fully isolate the user from the outside of the simulated environment (Mario et al., 2008).

A semi-immersive system, such as a large projection, provides 3D sound and high-resolution graphics. A large projection is a multi-user workplace surrounded by screens onto which the virtual world is projected. Images are displayed ac- cording to the position and gaze direction of the main user. In general, a semi- immersive system lets several users share the simulation; this opens up interesting possibilities for collaborative work (Mario et al., 2008).

Non-immersive systems have gained popularity due to their lower cost, ease of use, and ease of installation. They are sometimes called desktop-based VR systems; the most representative examples are video games. The combination of interactivity, ease of use, and appealing graphics and sound can produce in the users a great level of interest and involvement in the simulation (Mario et al., 2008).