Issue link: http://digital.copcomm.com/i/710451
www.postmagazine.com 27 POST JULY 2016 Summer B L O C K B U S T E R S Halsted says. "It doesn't break the silhouette. It just slides along." The techniques used to create Hank's simulation are likely to result in a SIGGRAPH talk this year. WATER The second challenge for the technical crew centered on water. When Pixar cre- ated oceans of water for Finding Nemo 13 years ago, 3D water simulation was in its infancy. For this show, the team concen- trated its efforts on water compositing. "The way we approach effects is that if the characters are in a large body of water, we do a smaller domain where they are playing," Halsted says, "a play area where they can jump around and break the water apart. So we worked on techniques for this film in which we take a large body of water usually shaped with procedural systems, and composite in the 3D simulation from the play area such that the boundaries are seamless." For fluid simulations, the team used SideFX's Houdini; for lighting, The Foundry's Katana; for rendering, RenderMan RIS. "We came up with a new system for doing the water composite that makes heavy use of an implicit field API to gen- erate the surfaces," Halsted explains. "We also worked on water shading to make sure the water looked as good as it could. And we made all this work with- in the new renderer." The fish in Finding Nemo spent most of the film in the ocean. Finding Dory's setting in the Marine Life Institute meant that often the fish in this film were in the aquarium's glass tanks. The lighting crew, led by Ian Megibben, put the new renderer through its paces for test shots with Dory in a fish tank and Hank staring in at her from outside. "There's an inherent quality to the way water bends, refracts, magnifies and scat- ters light," Megibben says. "Water inside a glass tank is like a fun house. There's mag- nification, distortion and reflections. When the camera is from Dory's point of view, we see reflections that create a boundary between her and Hank." Because Finding Dory is the first film for which Pixar used the RIS architecture, they employed Katana to author new shaders. "It was a huge change," says CTO Steve May. "It affected all the back-end depart- ments — lighting, rendering, shading. On Dino, we were still doing spherical har- monics and special shadow maps. Now, we're going to raytracing. "We felt like we were a little behind the curve," May continues. "But the good thing is that now we're right on the cusp, doing bi-directional pathtracing for the caustics. And, we're doing some work with volumes to make a large number of volumes very efficient." A de-noising filter developed by Disney Research and Disney Animation for use with Hyperion on Big Hero Six helped reduce computation time. "All pathtracers exhibit noise, and to eliminate it would take an enormous amount of computation," May says. "We have a real advantage in that we're part of a bigger company that includes Disney Research, Disney Animation and Industrial Light & Magic." Now, others can take advantage of that technology, too, which is available as a program called Denoiser with RenderMan. DÉJÀ VU ALL OVER AGAIN Sometimes, though, the new technology needed to comply with an older aesthetic. When the fish swim in a reef that repli- cates the environment from the first film, the lighters re-created techniques they had used a decade ago. "We forced a physically-based ren- derer to do something it didn't want to do," Megibben says. "Some of the engineers didn't want it to. But, we needed the reef to be familiar and safe. When we're in the MLI, we played with light and shadow, and the scenes have more contrast. We use backlighting and leave things in shadow. The reef is high key, almost comedic. It was a lot of fun to have two styles to play with between the two environments." With any sequel, the production crew has the problem of respecting the first film and expanding it to take advantage of tools and ideas they didn't have be- fore. And so, too, the writer and director. "The best thing about this film was reuniting with the people I had worked with," Stanton says. (Stanton had slipped away from Pixar to write and direct the 2012 live-action film John Carter.) "But also, to be honest," he adds, "it was learning new stuff about the charac- ters. It was like being with a cousin and hearing stories I'd never heard before." But, these characters weren't just cous- ins, as he realized in one brilliant moment. "It happened during our first scoring session," Stanton says. "I'm watching a finished section. The music is on. And there's a little separation, a rare moment. It was almost like looking at your kids the way the rest of the world sees them. It was the Nemo cue, the one moment in this film when we reference the first movie. I thought, 'Holy crap. I remember when I came up with him. With her.' I remembered the mundane office. These are characters everyone knows, but I had forgotten they came from me. It was profound." Barbara Robertson (BarbaraRR@ comcast.net) is an award-winning writer and a contributing editor for CGW. The Pixar team used different techniques for water and fluid simulations.