Visualizing a black hole not only takes a lot of imagination and a lot of data, it takes a tremendous amount of computing power, and the Charles C. Gates Planetarium in the Denver Museum of Nature and Science has plenty of each.
Since replacing its old star projector and going digital in 2003, it has relied on a 30-processor SGI supercomputer to generate the 11 blended images it takes to cover its 57-foot dome.
That recently changed with HP’s donation of a dozen of its new xw8400 dual quad core workstations, equipped with nVidia FX 5500 3D video controllers. It is, said Jeffrey Wood, HP’s director of product marketing for personal workstations, the first commercial application of the quad core systems.
The SGI system was powerful, but expensive to operate and maintain, said the planetarium’s operations manager, Dan Neafus. Everything was proprietary; if a video card failed, the replacement cost $20,000 – and the system had eleven graphics subsystems.
Zachary Zager, planetarium systems administrator, said that now each of the eleven DLP projectors is fed by a dedicated workstation with eight 2.4 GHz cores. The workstations are interconnected over gigabit Ethernet.
UniView, an expandable visualization platform developed by Sciss AB from Sweden and the American Museum of Natural History, replaces the custom-developed software used on the SGI system.
All this adds up to big savings for the planetarium.
“We’re always under pressure to lower costs,” said Neafus. “(The workstations) use 10 per cent of the power that the old IRIX (SGI) hardware did. And we don’t have to worry about $20,000 video cards.”
There could be other savings too, Zager added. Once the SGI systems are finally retired next June or July, he will re-evaluate the server room’s climate control, which currently blast out a lot of cold air to keep the supercomputer happy. With only a dozen more power-efficient systems to cool, the air conditioning won’t have as much to do.
Productivity has increased too. As well as being a showcase for productions, the planetarium develops content that is used by other planetariums as well as on television. These shows are digitally rendered and recorded for playback. Neafus said that tasks that used to take seven days were compressed to seven hours with the new workstations. “The trend in the end is to look at real time shows instead of pre-rendered productions,” he said.
That won’t be easy with the amount of data that has to be crunched. For example, in a relatively simple visualization of the positions of the Pioneer spacecraft over several years, 200 orbital positions must be calculated per frame, at 30 frames per second.
The planetarium’s developers have had to learn some new tricks to take advantage of the new hardware, Zager noted. “They have to learn to multi-thread everything.” Multi-threading is a programming technique that allows software to use multiple cores effectively.
The upgrades aren’t over yet. Zager plans to change the video connection to the projectors from VGA to DVI, eliminating the digital to analog conversion with its potential for signal degradation.
Planetarium shows are only the beginning, according to Neafus, who sees expansion of the museum’s productions into other areas of science. “We want to pursue all kinds of digital content.”
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