Virtual Reality
History and Development
Rather than having evolved from video games or flight simulation, the CAVE has its motivation rooted in scientific visualization and the SIGGRAPH 92 Showcase effort. The CAVE was designed to be a useful tool for scientific visualization. The Showcase event was an experiment; the Showcase chair, James E. George, and the Showcase committee advocated an environment for computational scientists to interactively present their research at a major professional conference in a one-to-many format on high-end workstations attached to large projections screens. The CAVE was developed as a "Virtual reality theater" with scientific content and projection that met the criteria of Showcase. The Showcase jury selected participants based on the content of their research and its suitability to projected presentation.
The challenge was attracting leading-edge computational scientists to use virtual reality. It had to help them get to scientific discoveries faster, without compromising the color, resolution, and flicker-free qualities they have come to expect using workstations. Scientists have been doing single-screen stereo graphics for more that 25 years; any virtual reality system had to successfully compete. Most important, the virtual reality display had to couple remote data sources, supercomputers, and scientific instrumentation in a functional way. In total, the virtual reality system had to offer a significant advantage to offset its packaging. The CAVE, which basically met all these criteria, had success attracting serious collaborators in the HPCC community.
How does it work?
Virtual reality may best be defined as the wide-field presentation of computer-generated, multi-sensory information which tracks a user in real time. In addition to the more well-known modes of virtual reality - head-mounted displays and binocular omni-oriented monitor (BOOM) displays - the Electronic Visualization Laboratory at the University of Illinois at Chicago introduced a third mode in 1992: a room constructed of large screens on which the graphics are projected onto two to three walls and/or the floor. Recently images have been projected onto all three walls.
The CAVE(tm)* is a multi-person, room-sized, high-resolution, 3D video and audio environment. In the current configuration, graphics are rear projected in stereo onto three walls and the floor, and viewed with stereo glasses. As a viewer wearing a position sensor moves within its display boundaries, the correct perspective and stereo projections of the environment are updated by a supercomputer, and the images move with and surround the viewer. Hence stereo projections create 3D images that appear to have a presence both inside and outside the projection-room continuously. To the viewer with stereo glasses the projection screens become transparent and the 3D image space appears to extend to infinity. For example a tile pattern could be projected onto the floor and walls such that the viewer sees a continuous floor extending well outside the boundaries of the projection-room. Three dimensional objects such as tables and chairs would appear to be present both inside and outside this projection-room. To the viewer these objects are really there until they try to touch them or walk beyond the boundaries of the projection-room. There are many rips and tears on projections screens where viewers have forgotten to be careful when walking within these invisible boundaries.
Specifically, the CAVE(tm) is a theater 10x10x9 feet, made up of three rear-projection screens for the front, right and left walls and a down-projection screen for the floor. Electrohome Marquis 8000 projectors throw full-color workstation fields (1024x768 stereo) at 96 Hz onto the screens, giving approximately 2,000 linear pixel resolution to the surrounding composite image. Computer-controlled audio provides a sonification capability to multiple speakers. A user's head and hand are tracked with Ascension tethered electro magnetic sensors. Stereographics' LCD stereo shutter glasses are used to separate the alternate fields going to the eyes. A Silicon Graphics Power Onyx with three Infinite Reality Engines is used to create the imagery that is projected onto the walls and floor.
Goals that inspired the CAVE engineering effort include:
* The desire for higher-resolution color images and good surround vision without geometric distortion
* Less sensitivity to head-rotation induced errors
* The ability to mix virtual reality imagery with real devices (like one's hand, for instance)
* The need to guide and teach others in a reasonable way in artificial worlds
* The desire to couple to networked supercomputers and data sources for successive refinement
"CAVE," the name selected for the virtual reality theater, is both a recursive acronym (Cave Automatic Virtual Environment) and a reference to "The Simile of the Cave" found in Plato's Republic, in which the philosopher explores the ideas of perception, reality, and illusion. Plato used the analogy of a person facing the back of a cave alive with shadows that are his/her only basis for ideas of what real objects are.
The CAVE premiered at the ACM SIGGRAPH 92 conference. It is achieving national recognition as an excellent virtual reality prototype and a compelling display environment for computational science and engineering data.
Technology Involved
Technical Specifications (of VA Tech Virtual Reality CAVE):
* Tracker 6 DOF
* Display resolution: 2500 x 2000 addressibility per screen
* Horizontal scanning frequency: 15-130 kHz
* Vertical scanning frequency: 38-180Hz
* Bandwidth: 125 MHz
* Dimensions: Operating position 104"H x 73.5" W x 84" D; Storage/Transport position 82" H x 73.5" H x 34"