August 5, 2004

By Charlotte Crystal

Greg Humphreys ponders ways to slice large problems into bite-sized pieces.

The U.Va. assistant professor of computer science works with super-sized sets of data to create visual displays, a process that requires major computing power. But instead of looking to traditional solutions – using an expensive supercomputer to crunch massive amounts of data, or simplifying the problem by reducing the amount of data involved – Humphreys has taken a new route. He harnesses off-the-shelf PCs to work in a “cluster” on separate pieces of a problem and later puts the pieces back together again. It’s like solving a giant jigsaw puzzle.

For his efforts in developing “Chromium” computer graphics software, Humphreys and a team of collaborators recently won a prestigious industry award, the R&D 100. The award, which recognizes the 100 “most technologically significant new products and processes of the year,” is bestowed annually by R&D Magazine, a publication based in Oak Brook, Ill., that reports on applied industrial research.

The goal of the award program, which reviews a broad array of technological innovations each year, is to highlight technology that advances and supports mankind, said Tim Studt, editor-in-chief of R&D Magazine and program chairman of the R&D 100 Awards.

In nearly every category of analysis, Chromium received top marks from the judges, he said.

“One judge called it ‘a killer application for cluster computing,’” Studt said. “Another judge noted that it was ‘a major advance in the state of the art,’ and ‘more efficient than anything else out there.’”

Just a few years old, Chromium is already widely used by industry, government agencies and researchers for a wide range of computer graphics applications, especially in manufacturing, defense simulations and medical science.

Humphreys, who joined U.Va.’s computer science faculty in 2002, initially developed the “freeware,” or freely available software, while completing his doctorate in computer graphics at Stanford University.

What Chromium does is to break down problems involving big sets of numbers into small packets of data, like pieces of a puzzle. The data is sent to a “cluster” of computers, individual PCs that are linked together in a local-area network. Each PC is fitted with an off-the-shelf computer graphics card that processes the data it was sent, working only on its own little piece of the puzzle. After the data has been converted into images, Chromium gathers the data from the individual computers and sends it to a projector or computer screen for display. In this way, the whole puzzle can be reassembled by using a number of projectors to display the individual puzzle pieces side by side, creating a composite picture. The data set is re-assembled as a visual display.

“Computer graphics are easy to explain but hard to do, which is what attracted me to this subfield of computer science,” Humphreys said.

One example of the software’s usefulness is seen at the Department of Energy, which funded the Chromium research and development. Under the international nuclear test ban treaty, the U.S. has agreed not to test its nuclear weapons. But the government still needs to know if the stockpile works. With Chromium, the analysts hook up a sufficient number of PCs into a cluster, process the data in pieces, and project it to a screen as a composite image.

Another application is appreciated by video-game enthusiasts, who like to watch video game competitions online. With Chromium installed on a home computer, a viewer can watch a game as it’s being played by professional game players, but change the representation of art on the screen into a blueprint style so that solid planes become open-line drawings, allowing the enthusiast to see through the roofs and walls of buildings, observing action that otherwise would be obscured.

One of the most important applications for this technology is scientific visualization, Humphreys said. Many scientists today run computer simulations to try to understand chemical or biological processes. But their initial results are often in the form of huge data sets that can be difficult to analyze and interpret. Using Chromium in combination with a computer cluster, they can create meaningful visual displays.

Chromium offers two advantages over traditional approaches to computer graphics, Humphreys said. First, it is cost effective. Computing power in off-the-shelf, personal computers has skyrocketed in recent years, making a lot of analytical power available for relatively little money. Linking them together further increases this capability.

Second, Chromium offers a way for researchers to create visual displays of data in real time without having to throw out reams of data to reduce the size of data sets so they can be manipulated quickly and easily.

Chromium is not alone in the world of cluster computing, as custom solutions for specific applications exist, Humphreys said. But Chromium is one-of-a-kind in its use of off-the-shelf hardware to run open-source software, which is free to the public. And it’s not copyrighted — users are free to modify it. In fact, it’s designed to be extended by its users, he said.

Along with Humphreys, the other developers named in the R&D 100 Award for “Chromium: Parallel, Distributed Open GL Rendering on Commodity Clusters” were Lawrence Livermore National Laboratory, Stanford University, University of Virginia and Tungsten Graphics Inc. The work recognized in the award was performed under contract with the U.S. Department of Energy.

As if developing computer graphics software weren’t enough to keep him busy, Humphreys has co-written a college textbook with Matt Pharr, a fellow graduate student from his days at Stanford. Five years in preparation, the book, “Physically Based Rendering: From Theory to Implementation,” is appearing this summer as part of the Series in Interactive 3D Technology by Morgan Kaufmann, a subsidiary of Elsevier Global Scientific and Medical Publishing.

Humphrey’s current research involves developing applications of Chromium for use in K-12 math and science education. Through a joint Technology in Education Program that brings together expertise from U.Va.’s School of Engineering and Applied Science and the Curry School of Education, Humphreys is working to enable school systems to provide educational graphics from a central location. He’s hoping to make it easy for a school system to invest in a cluster of computers, linked by a local-area network and served by Chromium, to transmit visual displays for mathematics and other courses to schools throughout the system.

In the classrooms, teachers could display the information on a variety of equipment, including inexpensive computer monitors, tablet PCs, personal digital assistants or a single projector, depending on their instructional needs.

Looking ahead, Humphreys believes it likely that in 10 years or so, “most flat surfaces,” such as walls or desktops, could be used as visual displays in the classroom.

He sees the field of computing coming full circle within 50 years. In the 1960s, there was a smaller number of huge, central mainframe computers. With the PC revolution, there was an explosion of small, but relatively powerful, decentralized terminals. In the coming years, the need for increasing power to analyze data and create graphics may lead again to the growth of centralized computing.

“ It doesn’t make economic sense to continue using powerful PCs; instead we’ll probably break the coupling between display and computer,” Humphreys said.

“What’s been holding us back has been the infrastructure of remote delivery,” finding cost-effective ways to deliver content to computer monitors from a distance.
And in the coming computer revolution, Humphreys hopes his path-breaking software will play a leading role in delivering accurate, affordable graphics to locations near and far.