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12 cgw n o v e m b e r . d e c e m b e r 2 0 1 6 open water, they turned to Splash, a system developed for this film. "We needed a new way to solve water," Driskill says. "Most of the commercially available solutions use one of two principal ways to solve water, and each has strengths and weaknesses. With one, we get fast solves that are easy to work with but can be unstable. With the other, we have more stability, but it's harder to work with and slower. Our technique takes the strength of both and integrates them. It's stable and fast." To render the water, the team built level sets into Hyperion, Disney Animation's proprietary renderer. "We start with a bazillion particles, then level sets cra a sur- face at the boundary of the particles that we built into Hyperion to create as much fidelity as possible," Driskill summarizes. "Rath- er than pre-solve the level set with some pre-set fidelity, the final level set, the choice of resolution, happens at render time." The team also provided controls for shaping and moving the water to get the type of motion and the look the directors wanted. "We layered white water on top and could dial in the looks of each layer, pulling out the right color and saturation for each piece of water," Driskill says. "We wanted to raise the bar. There was a recurring theme about how beautiful the water is in the South Pacific. People would say photos weren't doing it justice, that it was prettier in person. So, we aimed for their memory of the water, not a physical representation of the water. We have controls in Hyperion to break from physicality. We dialed in sub- tleties from shot to shot and sometimes in every frame to have water that was brighter, more saturated, and with reflectivity different from actual water, to give it more blue than what would naturally be reflected from the sky." PUSHING DATA The combination of simulation and rendering put extreme de- mands on the studio's renderfarm. "We built 70,000 cores in the renderfarm," Driskill says. "But even so, we bumped up against boundaries. We needed a peta- byte of temporary space for the water simulation and about ten times as much for simulation storage." Although the team could distribute the simulation across eight machines, each with 256 gb of RAM to achieve the fidelity they wanted, Hyperion couldn't handle distributed rendering. Thus, they created a monster machine that they used as a test bed. "We built a machine with a terabyte of RAM that we used to test-render some un-optimized shots," Driskill says. "We knew the upper limit on the farm, but people would blow out our memory, and we didn't know by how much. So, when we saw shots that needed more RAM, we'd take them over to the monster machine and find out how far out of whack the shot was." The complex environments on land pushed the limits, as well. Moana's fictional island of Motunui has more than 60 spe- cies of vegetation, including specific coconut trees, breadfruit, and taro. "We have a pretty mature system for vegetation using XGen and Bonsai, our procedural vegetation system," Driskill says. "We built Bonsai for Tangled. It's based on L-systems. But, the scope These are some of the exciting topics that will be covered in the Jan.-Feb. 2017 issue of Computer Graphics World magazine. ¢ GAME ENGINES – Powerful and versatile, today's game engines enable amazing projects both inside and outside the world of gaming. ¢ VFX – Go behind the scenes for a look at the cutting-edge visual effects in Rogue One: A Star Wars Story. ¢ DIGITAL SCANNING – Technology is playing a vital role in preserving the past. ¢ EDUCATION – How schools are preparing students for a career in computer graphics. ¢ MOCAP – The impact of new technology on motion capture. FOR ADVERTISING INFORMATION CONTACT OUR SALES TEAM MARI KOHN, DIRECTOR OF SALES 818. 291.1153 | mkohn@copcomm.com LISA NEELY, CORPORATE MARKETING & ADVERTISING SALES EXECUTIVE 818.660.5828 | lneely@copcomm.com WILLIAM R. RITTWAGE, PRESIDENT/CEO 818. 291.1111 | brittwage@copcomm.com next issue BONUS DISTRIBUTION AT GDC 2017