Scientific Visualization: Something to RAVE About

By John Quagliano, Dave Modl, Paul Argo, Laura Monroe, Steve Hodson, Jeremy Margulies, Dave Hite, Bob Greene, and Karl-Heinz Winkler, High Performance Computing Environments, CCN-8; and Robert Gurule, Scientific Software Engineering, CCN-12

Introduction

Fig. 1. Designed specifically for Los Alamos, this version of the RAVE is the only one of its exact kind and size in the world (for example, NASA-Glenn has a RAVE, but it is smaller).

Los Alamos uses many types of advanced technologies to gain new understandings of the physical world. Shown in Fig. 1, the RAVE (Reconfigurable Advanced Visualization Environment) is designed for scientists who need more sophisticated visual representations of complex data acquired through computations and experiments. The RAVE is part of the visualization facilities of the ASCI VIEWS program.

The RAVE was designed, built, and installed by Fakespace Systems Inc., the same company that built the Laboratory’s Powerwall and Immersive Workbenches. Conceived in the spring of 1999 (just after the Powerwall had been installed), the RAVE was completed in the fall of 2000 and was demonstrated the week before Christmas 2000. Unlike the Powerwall, the RAVE produces stereographic projections.

CCN-8 collaborates with various groups in other Laboratory divisions, including Advanced Computing, Scientific Software Engineering, Plasma Physics, Thermonuclear Applications, Computational Science Methods, and Weapons Engineering. CCN-8 also maintains contact with groups at Lawrence Livermore National Laboratory and Sandia National Laboratories. Academic and industrial partners include the University of Minnesota, University of New Mexico, SGI Inc., and Fakespace Systems Inc.

By sharing expertise with other organizations, the Laboratory can easily leverage the newest computer hardware and software technologies to best address the needs of scientists performing simulations requiring supercomputer resources. Additionally, half-hour-long demonstrations are routinely arranged for visiting VIPs in both the RAVE and the Powerwall; each month we typically host four to six groups of visitors.

Facility

The Los Alamos facility that houses the RAVE is quite large. The RAVE boxes take up approximately one-half of the available 60-foot square space. To help control the ambient lighting when the RAVE is used, our room has special track lights that can be (1) fully programmed or (2) controlled remotely.

Draperies form a 50-foot square around the center of the room and are approximately 14 feet high, running from the ceiling to the floor, and the floor itself has been carpeted. The projectors are low power and thus are very quiet. All these added amenities provide a pleasant workspace and make using the RAVE a comfortable experience.

Hardware Infrastructure

Although much like the CAVE system sold by Pyramid Systems, the RAVE has one principal difference: its pro-jection surfaces are not restricted to one place as in the CAVE, thereby permitting many display-panel orientations. (To download an MPEG movie that illustrates various configurations, go to www.fakespacesystems.com/products1.htm then click on the Workspace -> RAVE link). Each box has a footprint of approximately 10 feet by 12 feet to support the 10-foot square display screen.

The Los Alamos RAVE includes two floor panels for a true virtual reality experience. Possible configurations include a four-wall panel and a one-floor panel “closed box” arrangement, as well as two distinct “quarter box” (or “cove”) displays that consist of two wall panels and one floor panel each. Our primary configuration is a two-by-one setup resembling an “open-box” in which there are two displays across the front and one on each side. This configuration provides a viewing space of 20 by 10 feet across the front and the floor and 10-foot square on each left- and right-side panel. The current two-by-one configuration enables us to work in teams and give demonstrations to many people without getting too crowded.

The RAVE units contain an Electrohome Marquee 9500LC projector coupled with mirrors that produce an 18-foot light path to fill the 10-foot square (Fig. 2). These screens provided quite a challenge to get into the room during construction. Each screen weighs approximately 700 pounds; a special tilt-table with suction cup holders was built to move the glass into the room.

The RAVE is fed video and user interfaces from an SGI Origin 2000 computer containing ten Infinite Reality Graphics boards (six are used by the RAVE) located in an adjacent building. Signals are sent via fiber optics using Lightwave Video Display Extention systems. Daryl Grunau of the Advanced Computing Group has written a client-server PERL script that enables us to connect directly to the Infinite Reality Graphics boards in both single- or multi-pipe modes; the latter configuration is often required for interactive visualization of very large data sets.

Fig. 2. Dave Modl of CCN-8 tests the mirrors and projectors inside one of the RAVE boxes.

Visualization Software Applications

Following the installation of the RAVE, we dedicated several months to develop, adapt, and expand many software packages for it. To create a piece of software that could display on all surfaces, students at the University of Illinois-Chicago used a popular tool known as CAVELib (VRCO, Inc.) to create an immersive nature scene environment. The CAVELib tool permits immersive and interactive virtual reality scenes to be created for any non-flat multi-walled arena. CAVELib is an application programmers interface that provides general support for building virtual environments. It handles tasks such as drawing stereoscopic views and organizing multiple processes.

EnSight^® is a commercially available package (see www.ensight.com) that can use multiple flat screens to display images. The Laboratory has a site license for the Gold version of EnSight that runs in parallel on the SGI IRIX operating system. This package was used to project data sets collected from the Cerro Grande Fire (see this issue’s inside front cover).

Figure 3 shows a multi-wall application of a red giant star’s simulated structure. The data were computed at NCSA using the Piecewise Parabolic Method package to compute the physics and the Hierarchical Volume Rendering package from the University of Minnesota to create a stereo movie with the correct viewing parameters for the RAVE’s two-by-one display configuration. Paul Woodward and David Porter (University of Minnesota) and Stephen Hodson (CCN-8) collaborated to produce a short movie. This movie is displayed using a University of Minnesota moviola player modified to playback stereo pair images on multiple displays.

Silicon Graphic’s Volumizer package provides real-time interaction with jet data. Figure 4 shows a single time step that can be displayed on all the screens in the RAVE in stereo. Paul Argo (CCN-8) prepared the Volumizer demonstration to view and manipulate the raw volume data from the physics simulation. In this demonstration, the material’s transparency can be changed interactively by using the mouse controls.

John Quagliano (CCN-8) has implemented and expanded a tool known as the real-time ray tracer so that it can generate photorealistic ray-traced geometric objects in stereo mode (Fig. 5). This tool was originally developed by the University of Utah, one of the Laboratory’s partners under the ASCI alliance. Quagliano has taken this technology and coupled it with the RAVE. The ray tracer uses massively parallel resources to compute a display image’s subsections, which are subsequently assembled together to produce the full image. We have used as many as 64 of the 128 processors on the Nirvana visualization computer at the Laboratory to generate this particular image.

Fig. 3. A volume rendering of a simulated red giant star.

Future Work

We are exploring other options to connect the RAVE to other computer systems and expand its capabilities:

• Use a cluster of six Intel-based computers with 3Dlab’s Wildcat graphics cards to drive each of the six displays in the RAVE.
• Incorporate a position tracker system to track user’s movements in the RAVE.
• Add a surround-sound system to further enhance the immersive capability of the RAVE.
  
  

We also are working to adapt other software application packages to the immersive RAVE facility, such as CCS-1’s TRex high-performance parallel volume visualization tool (see www.acl.lanl.gov/viz/pr-trex) and CCS-1’s and Kitware.com’s parallelized vtk Visualization toolkit. We expect the vtk toolkit to integrate smoothly with the CAVELib resources. Finally, we are preparing for the eventual transition to the new Strategic Computing Complex, which will house the new Laboratory supercomputer.

Conclusion

Scientific data have become more complex and data set sizes are getting larger. Display systems used to visualize these data must try to keep pace so that scientists can understand what is being computed. The Fakespace RAVE display system, coupled with parallel software capable of interactive and immersive stereo renderings, can handle these growing visualization needs.

CCN-8 welcomes all inquiries concerning the RAVE. Karl-Heinz Winkler is the CCN-8 Group Leader and Laura Monroe is the Scientific Visualization Team Leader. We are available to discuss how this unique facility, coupled with the expertise of our visualization team, can assist in your scientific endeavors.

Fig. 4. Using SGI’s Volumizer, we created this gray-scale visualization of data shown in the background image found on this issue’s front cover.		Fig. 5. The real-time ray tracer, when coupled with the RAVE, can produce photorealistic ray-traced geometric objects in stereo mode.