Visualization tools: interacting with data in many dimensions

In ORNL’s CAVE, Ross Toedte (left) and John Drake examine the earth’s predicted surface temperature for a future month in a global climate simulation.(Photo by Curtis Boles). Click here for more photos.

Imagine walking into a CAVE virtual reality theater and feeling as if you’re flying in a kaleidoscope toward the red-hot core of an exploding star. As you meet up with the shock wave in this supernova, you see blobs of hot, reddish, rising material pounding on the shock wave and cooler, yellowish material moving inward. As you continue your flight to the core, some of this material falls back toward the center with you to be reheated by core-generated neutrinos, which drive the explosion. The yellow blobs accompanying you eventually turn red and move outward again.

Such an experience is available at ORNL’s CAVE, where four projectors throw full-color, computer-generated video streams onto three walls and the floor. Originally developed by the Electronic Visualization Laboratory at the University of Illinois at Chicago in the early 1990s, the CAVE (CAVE Automatic Virtual Environment) was designed to provide an environment in which multiple users could experience and interact with data in “natural” ways.

The CAVE uses a special blend of software and hardware to enable users not only to see but also potentially to hear and touch data. The CAVE floods the senses with information so users feel “immersed” or coexistent with data. Tracking hardware, such as headgear and a programmable joystick or “wand,” provides information about the user’s head position and orientation. This information is relayed from the hardware to a computer and used to calculate multiple realistic perspectives of a scene from the point of view of the user. Views are calculated for each wall and each eye to simulate a surrounding three- dimensional visual environment. The user wears special glasses that rapidly alternate between the left and right eye, thereby mimicking human depth perception. By moving and pressing on the wand’s programmed buttons, the user can choose an interactive experience such as flying or can select an object to learn more about it.

Ross Toedte and Ray Flanery, both of ORNL’s Computing and Computational Sciences Directorate, are programming the CAVE to provide interactive experiences for users in many applications areas, such as astrophysics and climate prediction. Toedte says his goal for ORNL’s CAVE is to find the ideal blend of data features and performance “so that meaningful images can be seen interactively. I am exploring various visualization tools to get the ideal mix of resolution and speed for each CAVE application.”

The CAVE is being used to help understand the intricacies of global climate change simulations. In the photograph below, ORNL researchers are looking at climate data calculated by colleagues at the National Center for Atmospheric Research. Color-coding helps deliver an understanding of parameters such as monthly surface temperature for a climate simulation between 1870 and 2170. Such simulations involve potentially hundreds of parameters. Because of the highly complex interrelationships among climate variables, subtle changes in just one can have magnified long-term effects. The CAVE provides an ideal environment for observing such sensitivities between multiple simulations and variables.

The CAVE at ORNL is being programmed to let viewers experience virtual stellar explosions. Scientists will be able to watch stellar explosions evolve from near the core or outside the shock wave. They will also be able to observe parameters such as temperature, density, and velocity in the supernovae simulations and compare findings based on both theoretical and experimental data. Eventually, it may be possible to understand how the elements that make life possible are synthesized and dispersed by such explosions.

Toedte and Flanery have used a number of visualization tools to provide insight into physical phenomena, help scientists verify calculated results, highlight the unexpected, and enable scientists to communicate their results more effectively. The immersive environment of the CAVE represents the high end of the visualization environment available at ORNL. This plethora of software and hardware tools offers large challenges and even larger potential for fostering meaningful scientific understanding through visualizing computational results.

Computation is now seen as an equal partner with theory and experimentation in the advancement of science; visualization helps bring this one-time vision to reality.