Indiana University      Research & Creative Activity      April 1998 Volume XXI Number 2



The CAVE

Researching with Perception, Reality, and Illusion


Imagine being inside of a molecule or viewing distant stars in faraway galaxies or exploring underground caverns in volcanoes or viewing the inside of a brain from any angle or even leaping over a building on the Bloomington campus as a quick shortcut to class. Well, virtually speaking, you can do more than imagine these images and situations in IU's Cave Automatic Virtual Environment (CAVE). You can actually see them in a virtual reality virtual environment.

CAVE
The IU CAVE measures eight feet in width, depth, and height and can accommodate several collaborators at the same time. High-resolution stereo images are projected onto the three walls and the floor and are synchronized with shutter glasses to provide the illusion of depth. A magnetic tracking system monitors the movements of the primary user, allowing natural interactions with the virtual environment or data set. --credit

Of course, campus shortcuts were probably not on the programmers' minds when putting together this three-dimensional architectural rendering of campus (the model for which was provided by the University Architect's Office) or the CAVE itself. The name CAVE is both an acronym and a reference to "The Simile of the Cave" found in The Republic. Here, Plato explores the concepts of perception, reality, and illusion using the analogy of a person facing the back of a cave. The wall of the cave is alive with shadows, which are the person's only basis for ideas of what real objects are.

On a practical level, Rick McMullen, director of the Advanced Information Technology Laboratory, says that immersive technologies such as the CAVE provide "new levels of visual presentation that offer additional insight to what your data is telling you." For instance, instead of a collection of graphs to show a series of observations, McMullen says another possibility is to present data as a collection of two-dimensional slices of time to illustrate how a data point changes over time.

Bringing an architectural rendering into virtual life doesn't even scratch the surface of the insight this interface will bring researchers and students alike. From simulating hurricanes and traversing the surface of Mars to nearly losing your stomach during a ten-second roller coaster ride and being hunted down by the angry bees you just knocked out of a hive, CAVE and other virtual reality (VR) and immersive technologies, such as the ImmersaDesk at Indiana University-Purdue University Indianapolis that allow users to "immerse" themselves in a virtual world of data, are providing new dimensions in teaching, learning, and research instrumentation.

In his research in crystallography, John C. Huffman, a senior scientist in chemistry and director of the Molecular Structure Center at IUB, says the immersive interface is ideally suited to work the most powerful processors researchers have--their own eyes and brains. "We may make hundreds of thousands of numeric observations that are used to create a model. We look at those results to decide where to go next," Huffman says. "In the VR environment, there is a visual process as the eye and brain interpret such a display of data."

He says visual representations are more efficient analysis tools than numbers in a list. "When looking from number to number to number, you don't know one is off until you look directly at it," he says. "If it's fit into a graph or highlighted with color, you can detect deviations at a glance. With immersion, you can look at so much more data simultaneously, and you are immediately attracted to deviations. It's easier and faster to tell the difference between two colors than two numerals. The eye is amazing at doing that, and it's an efficient way of analyzing data."

ImmersaDesk
The ImmersaDesk Facility at IUPUI is part of a major initiative in Virtual Reality and Virtual Environments (VR/VE). The ImmersaDesk is an immersive display device using a five- by four-feet rear projection screen and stereoscopic glasses attached to a high performance Silicon Graphics Onyx2 computer. This photograph shows Daniel Robertson (left), IDesk Team Leader, and John Hicks, Research Programmer, of the IUPUI VR/VE facility examining a brain reconstructed from the NIH Visual Human dataset using an application called vMRC. vMRC was developed by Robertson in collaboration with Michael Boyles, undergraduate research student, and Shiaofen Fang, Assistant Professor of Computer and Information Science at IUPUI. This application together with the ImmersaDesk allows biological datasets obtained from MRI, CT, or sectioned images to be interactively displayed and manipulated as stereoscopic high-quality three-dimensional images at larger-than-life sizes. These datasets can be visualized either as multiple cross sections or full semi-transparent volumes, as seen in the photo. --credit

Adding to the range of levels of analysis, sound can be used to reinforce concepts such as relative or changing distance between points. The Crayoland environment is a child's coloring book brought to virtual life--complete with brightly colored two-dimensional quacking ducks and bees buzzing angrily as they approach. In a three-dimensional molecular structure, sound can be used to illustrate relative distance between bodies. By selecting one point to be the center, sound can be used to signal when a radius makes contact with other cells as it gradually expands.

The CAVE was developed at the Electronic Visualization Lab at the University of Illinois at Chicago, and IUB installed the one in Lindley Hall in August 1997. It is one of an estimated twenty in the United States and fewer than forty in the world. While it's a mere eight-foot cube, a step inside shows new worlds and entire galaxies to be explored--at the touch of a button.

Four projectors display images reflected by mylar mirrors onto the three walls and floor of the cube. Each person viewing the CAVE environment wears a pair of battery-powered stereo shutter glasses, which filter the double image one eye at a time, forty-eight times per second to create the three-dimensional view. If several people are present, the group's leader is wired into the CAVE with a pair of goggles that synchronizes the view via an electromagnetic signal emanating from the top of the CAVE. The leader's perspective is shared by all. The input device is a wand with three buttons and pressure-sensitive joystick. These controls, combined with an antenna transmitting the wand's position and orientation, enable the leader to interact with and navigate in the VR environment. The Silicon Graphics system runs with six 195-megahertz processors and two graphic engines displaying up to 22 million triangles per second. Images are constructed with triangles, and this high display rate enables the image to appear more lifelike than traditional computer graphics.

Internet connections allow for collaborative work between different CAVE locations. "If we're working with observations of magnetic resonance imaging, we can show another site exactly what we're looking at, rotating the model as we discuss it, and relay instructions or comments almost in real time," McMullen says. "It is our hope that as more advanced computers become widely available, more collaboration and instruction will be accomplished in real time over the Internet."

Immersive technology makes laboratories and classrooms across the country or on the other side of the world instantly available. It also opens new opportunities for discussion and exchange.

"While doing research, such as solving a structure in crystallography," Huffman says, "we can watch over another lab's shoulder, sending them a note to correct errors we observe--maybe it should have been a nitrate instead of an oxygen molecule. Then, once completed, that model can be instantly accessible to other researchers over the network. Other labs can check our site to see what we've done, compare notes, and that way the whole network becomes a part of our instrumentation."

Whether using immersive technology as a classroom or a laboratory, solving structures in crystallography, or exploring the abilities and applications of the CAVE, one thing is for sure: this realm of technology is changing the nature of collaborative work--not just in research, but in teaching and learning as well. --Leigh Hedger


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