Visualizing the Universe: Hayden Planetarium achieves high-quality visualization with commodity hardware
Hayden Planetarium achieves high-quality visualization with commodity hardware
Seeing the night sky in upper Manhattan can be a challenge. However, for more than 70 years, the Hayden Planetarium at the American Museum of Natural History has provided one of the world's best views of the observable universe. In 2000, the Museum opened the Rose Center for Earth and Space, which was constructed
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Visitors at the American Museum of Natural History's Hayden Planetarium watch Cosmic Collisions. Image courtesy of D. Finnin/American Museum of Natural History.
The space show Cosmic Collisions premiered at the planetarium in March 2006, vividly demonstrating the impact, both literal and metaphorical, that collisions between astronomical bodies have had on the history of Earth and the solar system. Narrated by Robert Redford, Cosmic Collisions has the look and feel of a Hollywood production. However, unlike the latest summer blockbuster, the show was produced using data gleaned from actual astronomical observations.
Scientific visualization is the graphical representation of data in order to understand and gain insight into what it represents. Because humans are far better at comprehending information when it is presented graphically, rather than in numerical form, seeing the data in the form of an image can allow the researcher to — quite literally —gain insight that would not be possible with mere numbers. While it often utilizes the same software and hardware tools as do presentation graphics and entertainment applications, scientific visualization differs in important ways from both of these fields. Whereas presentation graphics and entertainment applications are primarily concerned with communicating information, scientific visualization is primarily concerned with understanding the scientific principles underlying the system that is producing the data.
In its space show presentations, the Hayden Planetarium blends the fields of scientific visualization, presentation graphics, and Hollywood-style animation. In so doing, it runs along the bleeding edge of several challenges facing the field of scientific visualization, namely
• real-time rendering of large data sets
• utilizing the processing power available in state-of-the-art graphics processing units (GPUs)
• creating effective real-time, human-computer interfaces.
Furthermore, the planetarium accomplishes this without resorting to large clusters of computers. Instead, these challenges are met by using off-the-shelf commercial hardware that takes advantage of a recent revolution in graphics processing power.
Visualization challengesAt the core of the planetarium's missions is the visual presentation of accurate scientific data. This visualization challenge is addressed through three distinct functions.
• straight-up scientific visualization used for real-time representation of data from the planetarium's Digital Atlas of the Universe. This is used directly in live public lectures and research, as well
as for fast "pre-viz" of material that will appear in planetarium shows.
• the synchronized projection of high-resolution images without seams or overlap. This would normally be a rather prosaic function if it were not for two factors — the size of the images, which are large by any standard, and the fact that image processing algorithms must be applied to any images or data displayed on the curved surface of the 100-foot dome to prevent distortion.
• the rendering of "digital dailies," or a run of production images each day for use by the production team in making decisions about the content of upcoming planetarium shows.
Selecting a systemPrior to the installation of the current system in 2005, the functions outlined above were performed by an SGI Onyx2 system. As this system reached the end of its useful life, the planetarium staff began scoping out a replacement system. Key requirements included
• genlock for synchronization of up to seven different video signals and the ability to project up to 4K x 4K resolution.
• the ability to grow and accommodate yet-to-be-defined features and requirements over its lifetime
• use of readily available, commodity hardware, both to keep system cost down and to improve long-term sustainability of the system.
At the end of the search, the staff selected a new visualization system based around dual AMD Opteron 250 CPUs and NVIDIA Quadro FX professional graphics boards with G-sync genlock option boards.
The system consists of eight PCs — seven workhorses for visualization and projection, and one for control and to serve as a backup. It relies on Linux for most tasks, but Microsoft Windows is
Real-time visualizationThe planetarium's Digital Atlas of the Universe is a database of all the known stars, galaxies and extragalactic objects in the observable universe. This information forms the core of the data presented in the planetarium's shows. The staff uses the new system's real-time functionality primarily as a "pre-viz" tool, producing accurate, but less visually appealing rough cuts of future shows that will be rendered with tools such as Autodesk Maya for the final version.
Additionally, the real-time functions are used for live presentations during public lectures, allowing speakers to go off script and present data in real time. When in this real-time mode, the system runs a Windows operating system and displays the data with Uniview, a visualization software package developed by the museum in conjunction with SCISS AB in Sweden. Uniview includes both a flight path tool for plotting a "course" through the universe as well as rendering features for production of high-quality visual detail.
Synchronized projectionThe most basic function of this system is to drive the planetarium's multi-channel projection system, which plays back seven synchronized, pre-rendered "movies," one for each of the planetarium's projectors — covering the theater's 100-foot-diameter dome with what appears to be a single, seamless, 3200 x 3200 resolution, 8-bit color depth image.
This fall, a six-projector system using cutting-edge projection technology will replace the current system, increasing the imagery's dynamic range from 8-bit color to 10-bit and its resolution to 4K x 4K. The planetarium's latest shows, including Cosmic Collisions, were rendered at 4K x 4K resolution with the expectation that this new projection system would be coming online.
"We know the data is present; we can see it on our monitors during pre-viz," says Benjy Bernhardt, director of engineering at the Rose Center for Earth and Space at the museum. "Unfortunately, the current projection system is unable to show it. We work at the highest quality and resolution so we can be as accurate as possible, and we know that the projectors will keep getting better and will be able to reveal more and more of the information. To that end, we use higher resolution and higher bit depth from the graphics side because we know that any flaws we have also will be revealed with the new projection system."
With projections for Cosmic Collisions, the staff began working 16-bit floating point EXR images into the production pipeline, allowing for a higher dynamic range and the ability to do gamma adjustments without introducing a lot of noise into the imagery. "Even though our projection system was not up projecting 16-bit, the key was to future-proof the content," explains Bernhardt. The NVIDIA Quadro FX boards were able to support these new requirements without replacement or modification.
Daily production images
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Streams of charged particles from the fiery surface of the Sun race toward Earth at over a million miles an hour in this image taken by NASA satellites. Image courtesy of the American Museum of Natural History/NASA.
"The system allows us to conduct our digital dailies, and it is reliable and actively supported," adds Bernhardt. "We were able to migrate to a modern cluster, and it is so fast compared to what we were used to in terms of taking our content and getting it into a viewable form. We were stunned. The disks read and write at the same time." This speed translates into untold advantages, particularly when the group is in production and needs to make decisions quickly.
From technical to conceptualAs Bernhardt points out, the group was able to put together a cutting-edge system, allowing the crew to experiment and revitalize the planetarium experience in a much smaller physical space and with lower cost, heat and power load.
"I'm not just talking about, ‘Gee whiz, look how fast we can fly through the data,'" says Bernhardt. "Rather, it enables us to get past just making things work so we can focus on the conceptual stuff beyond that, so we can ask ourselves, ‘What if we could do this, or that?' We needed a platform that is stable, modern and has forward growth. That's what we have with this system.
"The key factor is the commoditization of visualization, which is making professional quality visualization of data more broadly available. It's still something of a technical challenge — it's not easy to do, but high-quality scientific visualization is now within the technical and cost constraints of most research and educational institutions. We'll be seeing more applications like this in museums and science centers. This is particularly relevant in the field of climate studies, where public interest in the issue of climate change is exploding and is intersecting with an increasingly rich and growing set of climate data."
The visualization and projection system in place at the Hayden Planetarium admirably serves the dual roles of both research and education. It straddles the worlds of scientific visualization, presentation graphics, and Hollywood-style animation — providing the precision, accuracy and power to process large scientific data sets, then presenting them in a visually stunning form that informs as well as entertains. The key to this ability is not a large, expensive custom cluster of computers but, rather, a relatively small system based on commodity hardware.