Computer Graphics World

July 2009 25 CG Characters n n n n the same time, we add Komogorov noise using research on wavelet turbulence from a SIGGRAPH paper last year," Smith says. "e noise gets pulled through the fluid sim from frame to frame so it's coherent, and we get a nice movement with swirls at certain frequencies." By using volumetric rendering, in which every pixel is actually a stack of pixels going back into the camera with different densities, they could attach details from the sim to the camera view. Smith calculates that the 400-frame shot would take someone three years to render once on a PC equipped with a 2ghz pro- cessor. "We rendered it on eight-processor machines, so it renders faster. Not eight times faster, but faster." Breaking Bricks at is but one simulation in a sequence that sends the action way over the top— over the top of a pyramid in Egypt, as it happens. Devastator has learned that the machine everyone wants to find is inside the pyramid. e robot climbs up the side of the pyramid and smashes through the top, sending bricks flying and falling— 122,000 bricks, in fact, all simulated us- ing rigid-body dynamics (see Viewpoint, pg. 16). Until this film, the biggest simulation ILM had done using rigid-body dynam- ics destroyed a valley in Indiana Jones and the Kingdom of the Crystal Skull (see "Keys to the Kingdom," June 2008). is simu- lation was eight times bigger, and to ac- complish it, CG supervisor Chris Horvath wrote a rigid-body dynamics engine that ran in CUDA on Nvidia GPUs. By utilizing thousands of separate com- putation streams running at once, the en- gine could calculate the movement and collisions of thousands of objects through time. To destroy a clock tower in Paris, however, they ran a similar simulation in their in-house software, which is based on Stanford University's Physbam, to access high-level controls that were not needed for the pyramid destruction. "We love destruction," says Smith. "I remember showing Michael Bay some death-and-destruction simulations, and he said, 'You know, if I worked here, I would do that.' " Smith doesn't have a rendering analogy for shots of the Devastator with 52,632 moving parts causing 122,000 bricks in the pyramid to tumble down, but he does offer an overall fun fact. "If you looked at all the rendering we did for this film and tried to do it on one computer, a one-pro- cessor 2g PC, and you wanted to be done by the release date, June 24, 2009, you would have had to kick off the renders 16,000 years ago if you ran the computer 24 hours a day," he says. "Every night, we were pushing years and years of rendering time. It was really insane. We have hallways and hallways and racks and racks of hun- dreds of these machines going all the time. We broke all the ILM records." e 2008 Transformers needed 20tb of disk space. is film used 154tb. Crashing into Trees In addition to the Devastator sequences, Bay used IMAX cameras to film a forest fight between Optimus and two Decepti- cons. Animation director Scott Benza and his team choreographed the fights for the sequence, and Benza and Farrar supervised the plate photography in New Mexico. "One of the things we thought we could improve on from the first film was the fight choreography, the brutality of the fight," Benza says. "Michael really pushed making the fights as brutal as possible because they are machines. You can tear them from limb to limb and it's not as violent or disturbing as it would be if they were actors." Having Benza and Farrar involved in shooting plate photography helped the Rendering such complex robots as Bumblebee (top) and Optimus Prime (bottom), other CG objects, and simulations took 80 percent of ILM's rendering capacity. Including artist workstations, the studio can utilize 7700 core processors, the newest of which are dual processors and quad cores.

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