ATS Immersive Environments Lab

bcchang.com / ATS VRLab

About the CAVE and C-Wall

The CAVE

The lab's primary system is an immersive video projection display known as a C-Wall or GeoWall. The system has three main capabilities - stereoscopic display, hand and head tracking for immersive bodily interfaces, and spatialized audio for creating virtual soundscapes. The core of this system is based on the CAVE, a system of multiple stereoscopic projections developed at EVL in the early 90's, which has since become a worldwide standard for immersive, virtual reality systems.

The CAVE, and by extension the C-Wall, is an alternative approach to immersive environments from the head-mount display (HMD) technology commonly associated with 'virtual reality.' Using video projection rather than video helmets, the CAVE offers an alternative to the issues of disembodiment and isolation raised by HMD's. More amenable to group experiences and able to create connections between the virtual and physical worlds, the CAVE is perhaps more a part of a lineage going back to the artist Myron Krueger's VideoPlace installations than that of simulator displays.

Immersion and Body Interfaces

The two main aspects of the system are stereoscopic projection and the body tracking interface. Stereoscopic projection produces the illusion of depth, space, and presence of virtual objects. The goal of the body tracking interface is to map the presence and actions of the viewer's body into the virtual environment, as opposed to the usual abstractions of, for instance, the mouse and desktop interface. For example, to 'touch' an object on the screen using a mouse means moving an object on a horizontal plane to make an image move on a vertical screen nearby to intersect another image on that screen. In the CAVE, this prosthetic chain of abstractions is shortened - you just move your hand to the point in space where the image appears to be. More than an attempt to create more "intuitive" or "natural" interfaces, this system plays a crucial role in creating the fragile sensation of presence through kinaesthetic reinforcement. And, while virtual reality may appear to be culmination of a desire to sever consciousness from matter through weightless visual illusion, the body tracking interface may provide a counterbalance by placing a new focus on the role and actual existence of the body itself.

Tracking

In practical terms, the interface technology that the CAVE uses is a magnetic tracker system, which combines an electromagnetic transmitter with a number of small receivers. The tracker can tell the precise position and orientation of each of the receivers, which are attached to glasses, headbands, gloves, pointing devices, or other points on the viewer's body. A common basic configuration is to use two sensors - one to track the viewer's head, and another to track one hand.

The CAVE and the C-Wall

The term "CAVE" refers to a specific configuration of equipment, with stereoscopic projections on multiple walls and often the floor and ceiling as well to create a completely immersive visual field. Originally built using SGI Onyx supercomputers costing hundreds of thousands of dollars, CAVEs can now be built using clusters of standard PC desktop or workstation computers. The term CAVE is now often used generally to refer to other, similar immersive systems using one or more stereo projection screens. A simplified form of the CAVE uses just one screen, making it significantly more affordable, easy to install, and easy to transport; this type of system is often called a C-Wall or a GeoWall due to its popularity in the geological scientific community. This type of system can be built using an inexpensive PC and commonly-available video projectors, with the most expensive components being the magnetic trackers.