Virtual Reality

The term 'Virtual Reality' (VR) was initially coined by Jaron Lanier, founder of VPL Research (1989). Other related terms include 'Artificial Reality' (Myron Krueger, 1970s), 'Cyberspace' (William Gibson, 1984), and, more recently, 'Virtual Worlds' and 'Virtual Environments' (1990s).

Virtual Reality (VR) research and development is a rapidly evolving field. New display technologies and interaction devices are continually being produced and modified, redefining the way in which participants view, navigate and interact within Virtual Environments (VEs). Virtual Reality (VR) is an all-encompassing term which describes the technology and the field of application in general, but essentially VR replaces the real world with a synthetic computer generated environment. VR is an interface which combines diverse technical systems with the goal of enabling users to interact in real time within Virtual Environments (VEs). VEs are three-dimensional computer-based environments representing applications for visualization, animation, generation or modification of real or abstract objects/ situations.

Benefits of VR:

• VR may be used where manipulation of real-life variables would risk damage to people, equipment or the environment (eg. in hazardous environments)
• VR can provide an alternative where manipulation of real-life variables has an unacceptably high associated resource cost (eg. logistics, finance, personnel or national security)
• VR allows rapid prototyping and configuration of an environment where perceptual input might need to be changed frequently (eg. reconfiguring interface details or instrument layouts)
• VR allows users to experience views of micro or macroscopic entities in a variety of dimensions (eg. using VR to explore the atomic surface of materials or human tissue at a nanoscopic level, in a way that would not be physically or ethically possible in the real world)
• VR can be used where real locations are impossible or difficult for users to physically occupy (eg. hazardous environments, simulating outer space, under the sea, etc)

Technology Description:

As technology advances, it is difficult to talk about a singular 'VR system' as modern systems are made up of a number of different components depending on the user requirements for specific VR applications. A typical VR system consists of at least the following components:

• Computer - the most popular graphics computer for VR systems is still an SGI Onyx, but rapidly growing capabilities of consumer graphics hardware in the PC segment, now allow the rendering of complex, texture-rich virtual worlds on this comparatively cost effective hardware platform in real-time.
• Visual display - different visual displays are available for VR systems, typical examples include a standard CRT monitor, an HMD, a projection screen or a ´reality theatre´ or CAVE.
• Input device(s) - are necessary in order to navigate and interact in the VE. There is a wide range of devices available and those selected will be affected by the display device that has been chosen for the system. For example, if an HMD is used, an input device would need to compliment it so that the participant would not be required to look at it to understand its operation (e.g. a detailed keyboard). Conversely, a desktop system would tend not to be used with a tracked input device as there is limited space for movement available.
• Software - sophisticated software is used to run VEs in real-time. Software is also used for tracking or force feedback (where this is used). The VE software must coordinate the inputs from the participant's movements and interactions and update the VE accordingly using real-time rendering and displaying of the VE.

Common VE Systems:

Desktop system
A typical desktop system uses a standard CRT monitor (or LCD laptop screen) as the display device. The participant is not enveloped in the VE but has a 'window' into the VE. Interactivity and navigation are achieved either via advanced PC input devices such as the Spacemouse or multi-axis joysticks. Alternatively the VE interface can be designed to incorporate icons that allow the participant to navigate or interact in the VE using standard PC input devices (mouse, standard joystick or keyboard etc). Specialised software packages allow VEs to be created and run on desktop PCs.

The Virtual Colonoscopy project allows doctors to visualize MRI data to check a patient's colon for polyps.

HMD System
A typical Head Mounted Display (HMD) consists of a helmet with two small displays (CRT or LCD) and an adjustable lens system. HMDs are the first projection systems which have been developed specifically for viewing VEs. They can produce stereoscopic viewing by presenting separate overlapping images to each eye. They are widely used for military and medical applications. They vary in cost, and some devices can be desirable and affordable for home users as display devices for 3D games. Interaction and navigation are achieved through specialised input devices, for example 3D mice, wands or data gloves.
The HMD and the input devices are tracked in real-time using an electromagnetic tracking system which is transformed by the computer to update the participant's position within the VE. HMD systems are usually used by single participants, however it is sometimes possible for multiple participants to inhabit the same virtual environment.

On the right, a head mounted display.

BOOM
The BOOM (Binocular Omni-Orientation Monitor) from Fakespace is a head-coupled stereoscopic display device. Screens and optical system are housed in a box that is attached to a multi-link arm. The user looks into the box through two holes, sees the virtual world, and can guide the box to any position within the operational volume of the device. Head tracking is accomplished via sensors in the links of the arm that holds the box.

Projection system (power wall, holobench, L-shaped systems, etc)
In a typical projection system, the VE is projected onto a free-standing or wall-mounted projection screen via conventional three-tube video projectors.
The VE can be viewed by a number of participants at any one time, depending on the size of the projection screen and the space available.
The VE is usually manipulated and interacted with by one participant with the remaining individuals as passive observers. Navigation and interaction typically takes place using standard PC input devices, however more sophisticated devices can be used. There are many types of systems that come under the generic heading of projection systems, these are generally classified according to the display type.

The Center for Visual Computing's Virtual Workbench.

CAVE
2 - 6 walls (fabric or plastics) form a projection area or room (CAVE). CAVE systems consist of two or more walls and a walkable floor all with rear projection. Compared with a power wall the floor and additional walls extend the interaction volume and therefore the sense of immersion. In particular a 6-sided CAVE requires wireless tracking, interaction and sound devices. In contrast to dome-like or curved screen systems, the flat walls guarantee a defined undisturbed projection. Reconfigurable systems combine the advantages of different projection systems. They can be more or less easily adjusted to meet application specific requirements.

Input Devices:
A variety of input devices like data gloves, joysticks, and hand-held wands allow the user to navigate through a virtual environment and to interact with virtual objects. Directional sound, tactile and force feedback devices, voice recognition and other technologies are being employed to enrich the immersive experience.

5DT data glove.

Immersive Virtual Reality:
Head-referenced viewing provides a natural interface for the navigation in three-dimensional space and allows for look-around, walk-around, and fly-through capabilities in virtual environments.

Stereoscopic viewing enhances the perception of depth and the sense of space.

The virtual world is presented in full scale and relates properly to the human size.

Realistic interactions with virtual objects via data glove and similar devices allow for manipulation, operation, and control of virtual worlds.

The convincing illusion of being fully immersed in an artificial world can be enhanced by auditory, haptic, and other non-visual technologies.

Non-immersive VR:
These applications include mouse-controlled navigation through a three-dimensional environment on a graphics monitor, stereo viewing from the monitor via stereo glasses, stereo projection systems, and others. Apple's QuickTime VR, for example, uses photographs for the modeling of three-dimensional worlds and provides pseudo look-around and walk-through capabilities on a graphics monitor.

QTVR view of the Student Activities Center.

An anaglyph QuickTime VR object. Requires red/blue glasses to view properly.

VRML:
VRML provides three-dimensional worlds with integrated hyperlinks on the Web. The viewing of VRML models via a VRML plug-in for Web browsers is usually done on a graphics monitor under mouse-control and, therefore, is not fully immersive. However, the syntax and data structure of VRML provide an excellent tool for the modeling of three-dimensional worlds that are functional and interactive and that can, ultimately, be transferred into fully immersive viewing systems. The current version VRML 2.0 has become an international ISO/IEC standard under the name VRML97.

VR-related Technologies:
Other VR-related technologies combine virtual and real environments. Motion trackers are employed to monitor the movements of dancers or athletes for subsequent studies in immersive VR. The technologies of 'Augmented Reality' allow for the viewing of real environments with superimposed virtual objects. Telepresence systems (e.g., telemedicine, telerobotics) immerse a viewer in a real world that is captured by video cameras at a distant location and allow for the remote manipulation of real objects via robot arms and manipulators.

References:

K.P. Bier
http://www-vrl.umich.edu/intro/

http://www.view.iao.fhg.de/introduction.html