Other VE systems project images on the walls, floor and ceiling of a room and are called Cave Automatic Virtual Environments (CAVE). The University of Illinois-Chicago designed the first CAVE display, using a rear projection technique to display images on the walls, floor and ceiling of a small room. Users can move around in a CAVE display, wearing special glasses to complete the illusion of moving through a virtual environment. CAVE displays give users a much wider field of view, which helps in immersion. They also allow a group of people to share the experience at the same time (though the display would track only one user’s point of view, meaning others in the room would be passive observers). CAVE displays are very expensive and require more space than other systems. A Cave Automatic Virtual Environment (better known by the recursive acronym CAVE) is an immersive virtual reality environment where projectors are directed to three, four, five or six of the walls of a room-sized cube
Engineers from Sun Microsystems and Fakespace Systems created this awesome immersive virtual environment that looks very much like the Holodeck in Star Trek!
• GENERAL CHARACTERISTICS OF CAVE
The CAVE is a 10’ X 10’ X 9’ theatre that sits in a larger room measured to be around 35’ X 25’ X 13’. The walls of the CAVE are made up of rear-projection screens, and the floor is made of a down-projection screen. High-resolution projectors (the University of Illinois uses an Electrohome Marquee 8000) display images on each of the screens by projecting the images onto mirrors which reflect the images onto the projection screens. The user will go inside of the CAVE wearing special glasses to allow for the 3-D graphics that are generated by the CAVE to be seen. With these glasses, people using the CAVE can actually see objects floating in the air, and can walk around them, getting a proper view of what the object would look like when they walk around it. This is made possible with electromagnetic sensors. The frame of the CAVE is made out of non-magnetic stainless steel in order to interfere as little as possible with the electromagnetic sensors. When a person walks around in the CAVE, their movements are tracked with these sensors and the video adjusts accordingly. Computers control this aspect of the CAVE as well as the audio aspects. There are multiple speakers placed from multiple angles in the CAVE, giving one not only 3-D video, but 3-D audio as well.
The CAVE
The first CAVE was developed in the Electronic Visualization Laboratory at University of Illinois at Chicago and was announced and demonstrated at the 1992 SIGGRAPH. The CAVE was developed in response to a challenge from the SIGGRAPH 92 Showcase effort (and its chair James E. George) for scientists to create and show off a one-to-many visualization tool that utilized large projection screens. The CAVE answered that challenge, and became the third major physical form of immersive VR (after goggles 'n' gloves and vehicle simulators). Thomas A. DeFanti, Daniel J. Sandin, and Carolina Cruz-Neira are credited with its invention. It has been used and developed in cooperation with the NCSA, to conduct research in various virtual reality and scientific visualization fields. CAVE is a registered trademark of the University of Illinois Board of Regents.
• TECHNOLOGY
A lifelike visual display is created by projectors positioned outside the CAVE and controlled by physical movements from a user inside the CAVE. Stereoscopic LCD shutter glasses convey a 3D image. The computers rapidly generate a pair of images, one for each of the user's eyes. The glasses are synchronized with the projectors so that each eye only sees the correct image. Since the projectors are positioned outside of the cube, mirrors often reduce the distance required from the projectors to the screens. One or more computers, often SGI workstations, drive the projectors. Clusters of desktop PCs are popular to run CAVEs, because they cost less and run faster.
• DEVELOPMENTS IN CAVE RESEARCH
The biggest issue that researchers are faced with when it comes to the CAVE is size and cost. Researchers have realized this and have come up with a derivative of the CAVE system, called ImmersaDesk. With the ImmersaDesk, the user looks at one projection screen instead of being completely blocked out from the outside world, as is the case with the original CAVE. The idea behind the ImmersaDesk is that it is a single screen placed on a 45-degree angle so that the person using the machine has the opportunity to look forward and downward. The screen is 4’ X 5’, so it is wide enough to give the user the width that they need to obtain the proper 3-D experience. The 3-D images come out by using the same glasses as were used in the CAVE. This system uses sonic hand tracking and head tracking, so the system still uses a computer to process the users’ movements.
This system is much more affordable and practical than the original CAVE system for some obvious reasons. First, one does not need to create a “room inside of a room”. That is to say that one does not need to place the ImmersaDesk inside of a pitch-black room that is large enough to accommodate it. One needs one projector instead of four, and only one projection screen. One does not need a computer as expensive or with the same capabilities that are necessary with the original CAVE. Another thing that makes the ImmersaDesk attractive is the fact that since it was derived from the original CAVE, it is compatible with all of the CAVE’s software packages and also with all of the CAVE’s libraries and interfaces.
