Virtual Reality, commonly called VR, uses advanced graphics to deliver an immersive environment -- a computer generated world that you can literally walk into! Verging on science fiction, a high end CAVE system (Computer Aided Virtual Environment) is much like a Star Trek Holodeck. They are used for scientific visualization in many fields and for training -- for example, NASA uses a CAVE to train astronauts for shuttle missions.
Most CAVE systems are in Universities or government labs. Some major companies such as General Motors and John Deere have visualization facilities that include a CAVE. Very few CAVE systems are available for commercial use; an exception is the installation at Delta Search Labs in Cambridge, MA, which is used for both internal research and is available for commercial applications.
I managed projects to apply the CAVE to molecular modeling, mechanical visualization, architectural visualization, industrial design, and flow visualization, and evaluated a range of CAVE-enabled applications for commercial potential. I also directed the development of new user interface tools and projects to improve application performance.
CAVE TECHNOLOGY
A CAVE visualization environment is actually a room that you can walk into, typically 8-10 feet wide. It incorporates a multi-wall display that puts you completely inside the scene. A CAVE will typically include 3-6 walls; Delta Search Labs has a four wall CAVE, and Iowa State University has a six wall CAVE in their VRAC (Virtual Reality Applications Center).
There are three factors that separate CAVE systems from ordinary visualization: immersion, stereo viewing, and tracking.
A key aspect of immersion is that it engages both direct vision as well as peripheral vision. Unlike a regular computer monitor, or even a large screen projection, a CAVE lets you look around and even walk around. The images blend seamlessly across the corners of the room and across the floor.
Stereo viewing requires that the graphics system deliver separate images to the left and right eye. The images are calculated based on the position of each eye, and are slightly separated. This results in depth to the image, causing it to pop out of (or in to) the display. Stereo viewing can be done on regular computer monitors by using special LCD shutter goggles, such as the CrystalEyes glasses from StereoGraphics Corporation. These are widely used in a number of industries, such as molecular modeling.
One of the biggest limitations of traditional stereo graphics is that it assumes a fixed viewing position -- it assumes that the viewers head is in a fixed location. The resulting scene is correct for this head position, but incorrect for any other locations. This produces visual anomalies, and an unnatural image when you move your head.
CAVE systems address this by adding head tracking, using special hardware which determines where the users head is located (in three-dimensional space) and which direction he is looking in. By using this information, the computer can calculate the correct view for the users actual location. For realistic images, the head tracker has to be accurate, smooth, stable, and provide rapid updates.
A CAVE pulls all of these elements together. The result is incredible realism. Not only does the computer generated image seem to be real, but it is actually possible to physically walk around an object and examine it from all sides!
The visualization power of a CAVE can be used in many ways: car companies use it for styling and for consumer testing of car interiors. It is also used to understand things that can't actually be seen, such as molecular modeling or the flows produced in computational fluid dynamics analysis.
CAVE Power
A CAVE system demands massive computer and graphics power. While an ordinary desktop computer or workstation can drive a single display, a CAVE requires 6-12 separate displays that are tightly integrated into a single image and updated 30-60 times each second. This is usually done using specialized systems such as SGI Infinite Reality or Evans and Sutherland Harmony. Much research is occurring to use PC graphics, such as the Chromium extension to OpenGL for cluster based rendering.
The combination of PC based graphics and rapidly falling prices on projection systems is enabling widespread use of large systems. The greatest limiting factor today is in head tracking systems, as no good, inexpensive trackers are yet available. However, considering the progress being made in many fields, it is reasonable to expect CAVE systems to become much more widely used.