What is VR?

Introduction and overview

Rheingold, H. (1991). Virtual Reality. London: Secker and Warburg/Mandarin.

A History of Virtual Reality

a short history of VR considering not merely a history of the technologies but also of the human aspects: the nature and appeal of illusions, the caves of Lascaux and Altamira, paper-based visualization, early Greek theatre

Readings:
'VRMLWorks: The History of VRML' -- a good directory of URLs on the history of VR
» http://vrmlworks.crispen.org/history.html

1. What is ‘virtual reality’?

Virtual Reality, a term coined by Jaron Lanier around 1989, is today used to refer broadly to a wide range of technologies and experiences, including non-graphical ‘worlds’ such as those of IRC. In this document, and throughout the course, we shall paradigmatically think of VR as a computer-generated 3D graphical environment rendered in real time in response to the behaviour of the user, and the term will be used in that sense unless the context indicates otherwise. However, we shall also be considering other kinds of virtual reality, pre-eminently QuickTime VR.

There are several varieties of VR as defined in the strict sense above. Such a virtual environment may be:

  • desktop (screen-based, e.g. computer)
    Also known as 'fishtank VR' and 'Window-on-the-World' (WOW) VR, desktop VR characteristically uses a standard computer monitor as a ‘window’ onto the virtual world. The user can change the position and orientation of the monitor window in the virtual world in real time using a variety of input devices from the keyboard to 6 degree of freedom forceballs. In addition the standard monitor graphical display, the user can use shutter glasses or similar to view the display stereoscopically. 3D sound can be played through stereo headphones or speakers, and desktop devices are even available to allow the user to have a sense of touch in the world. Although generally not as technologically immersive as ‘full immersion’ systems, desktop VR only requires a minimum of a standard PC or workstation and the correct software, allows the user to work without the encumbrance of head mounted displays, and also allows easy switching of attention between the real and virtual worlds.

  • projection VR (e.g. 'Reality Room')
    If the field of view of the computer display is wide enough, then the effect is not of looking at a display but of actually being within the scene. Although HMDs can provide a wide field of view display, they have a number of disadvantages related to their use. Wide field of view images can also be obtained by projecting a high resolution display onto a large, curved screen, using multiple projectors. Since more than one user can look at the same screen at a time, experiences can be shared and work can be performed collaboratively. The CAVE system uses a slightly different approach where the image is back-projected onto three walls of a small room, creating a field of view equal to around 270°. Stereoscopic shutter glasses can be used with both systems to create a ‘more three dimensional’ view. Although the experience produced can be extremely effective, the illusion is broken if the user looks away from the screen. Another problem is that synchronising the multiple projectors used in the display can be problematic and the view will only be correct from one position, resulting in an imperfect view for users sharing the system.

  • immersive (with head-mounted display, dataglove, bodysuit)
    This is the most popular image of VR, using a head mounted display (HMD), head tracker, and glove or other flying input device. The image of the virtual world is displayed on small screens mounted in the HMD in front of the user’s eyes, and optics are used to focus the image at a comfortable distance and enlarge to fill a wide field of view. As the user moves their head around, the change of position and orientation are sensed by the host computer using the head tracker, and the scene rerendered in real time according to the new viewpoint. The user can control their virtual hand by using a glove or flying mouse with their real hand. Interaction in the real world can be by using gestures in glove systems; floating menus in other systems; or, more rarely, voice recognition. 3D sound can also be generated according to the users viewpoint, and heard through stereo earphones mounted on the HMD. Although these systems are one of the most immersive general purpose interfaces, they have a number of disadvantages. More than one system is required for others to share the experience, most HMDs provide a picture quality worse than the average computer monitor, and the system can be uncomfortable to use for extended periods due to the encumbering hardware required.

  • ‘environmental’ (virtual environment embedded in real environment, e.g. CAVE).
    The latter may be either ‘encumbered’ or ‘unencumbered’, depending on whether the user is required to wear additional devices (e.g., head-mounted display).