Issue link: https://digital.copcomm.com/i/4522
November 2009 29 Visual Effects n n n n structure emits the water and acts as a kind of controlling force. "It's like having a magic hand inside the Navier-Stokes flow," Trojansky says. Because the tidal wave was so huge, the R&D team devised techniques to compute one frame on as many networked machines in the renderfarm as the group wanted, and thereby achieve massively parallel simula- tions. ey also invested time into im- proving the infrastructure. "A single frame might use 50gb of data, and a single shot, 20tb," Trojansky says. "So we created our own server system with a throughput of 4gb/sec and 1.2 petabytes of disk storage. at meant we could re-run a shot in one to two days rather than one to two weeks." In addition, the R&D team developed technology for retiming the simulation. "On many occasions, even after we had ap- proval on the postvis, we'd hear, 'We love it, love it, love it. But can't you do it in 12 f rames per second?' " Trojansky says. "Or, '18 frames per second?' We wanted to print T-shirts that said, '18 fps looks better.' " e problem was that time steps drive the simulation, so changing the time steps changes the behavior—that is, the look of the simulation. An easy way to visualize this is to imagine throwing a cup of wa- ter out the window of a car. If the car isn't moving, the water streams down. If the car is moving fast, you create a trail of droplets and mist. "e worst thing was to hear, 'I liked the look of the previous version and t he speed of the current version,' " Trojan- sky says. "So we created a way to compen- sate for the new timing in the solver, and the slower simulations looked the same." To speed the approval process, the R&D team also developed a better way to refine rough simulations. "In traditional simulation systems, you do a rough version for quick feedback and then re-run it in higher reso- lution," Trojansky says. "But each time you run it, the simulation looks different because you can't scale the detail without affecting the timing, which is what the client wants most. We developed an iterative approach. Our first version drives the next version, which drives the next version, and the main characteristics of the movement stay the same. We can go finer and finer until we're at a droplet level, until the mist blows off the wake." In addition to the Himalayan simula- tions, Scanline built environments and an- imated crowds for the sequence in which a tidal wave sends an aircraft carrier crash- ing into the White House. "We not only had water flowing through the city, but also a crowd of refugees on the ground, trees bending and interacting, the aircraft carrier reflecting and refracting, airplanes falling into the water, and burning houses from the previous earthquake. We even had to sweep away the American flag on the roof of the White House." e rules were the same as in the real world: the stronger object wins. In other words, the flag wouldn't affect the tidal wave, but parts of the building would. To animate the crowds, Scanline used Massive software, as they did to create a fugitive trail of 10,000 people in India fleeing the tidal wave rushing toward the Himalayas. "I think that's where you see the most digital people killed at one time," Trojansky says. "is show pushed us on every level," Trojansky adds. "With some visual effects work, you can just hire more animators and modelers. In this highly specialized complex work, it's so much about the hardware and software technology, and the people who can drive it. It was a big step for our team to reach this scale." During a panel session at Nvidia's recent GPU conference, ad Beier, CTO at Digi- tal Domain, described 2012 as one of the best visual effects demo reels ever. As Digital Domain's Leo pointed out, the film proves that computer graphics can replace minia- tures to create this kind of destruction. And, it shows that with the help of faster hard- ware, clever software, and adept artists, di- rectors can now think about using natural phenomena as characters in ways they might not have imagined only a few years ago. At the end of the film, Engel and Wei- gart disbanded Uncharted Territory, as they always do at the end of their projects, but this time, they didn't sell the machines. "We tried to talk Sony into selling them," they say. "We told them, 'is works be- cause we always buy the newest machines and there will be something newer that's twice as fast for the next movie.' ey said, 'We don't want you to touch a thing. Leave it all exactly as it is.' So, all the machines are still there in this empty room. No people. But, of course, it's all about the people." n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. Scanline VFX created and simulated the interaction of the digital water with the mountains, arks, Air Force One, debris, snow, and mudslides in the climactic all-CG shots.