The Extreme Science and Engineering Discovery Environment (XSEDE) held their annual conference in St. Louis last week. David Bock’s photorealistic thunderstorm visualization took home the people’s choice award for best visualization.
Bock, senior visualization programmer for the US National Center for Supercomputing Applications (NCSA), worked from a simulation by Leigh Orf, research scientist at the Cooperative Institute for Meteorological Satellite Studies at the University of Wisconsin. (Orf’s breakthrough simulation of a supercell producing a long track EF5 tornado can be seen here.)
Orf used the CM1 cloud model to compute 2,200 x 2,200 x 380 data points on a rectilinear grid across 800 time steps, solving for cloud and precipitation, pressure, winds, and temperature. His simulation used 20,000 cores on NCSA’s Blue Waters and produced about 100 TB of data.
“One of the ways to validate a numerical simulation is to visualize the model data in ways that match observations,” Orf says. “If you can't get a simulated storm to look like a real storm, then there is something wrong with the model or the technique you are using. If you can get them to look similar, it lends much more credence to the simulation and its faithful representation of the atmosphere, the storm, and what goes on inside the storm.”
To represent features like the way light and shadow play inside and outside of a storm cell, Bock ported his custom rendering system to Blue Waters — honoring both the physics of the thunderstorm cloud and the painstaking computations by Orf. “I call it ‘sim-realistic,’” says Bock of his results.
Whereas typical visualizations offer a Newtonian color map with blue signifying a low value and red representing a high value, photorealism makes it easy to see how light scatters throughout the supercell or the massive separate ice storms in the upper atmosphere.
Sim-realism is not merely an aesthetic preference for Bock, however. Seeing a realistic rendering aids comprehension, because “as soon as you see the storm, you recognize and connect aspects of the storm that you see in real life with the computational model,” says Bock. “If it’s a thunderstorm, then it should look like a thunderstorm.”
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18 hours 52 min ago