Issue link: https://digital.copcomm.com/i/30784
n n n n CGI To render the trees, crowds, hair, fur... Animators used eyelid controls to hand-sculpt shapes across the eyeball for characters such as Nigel, the villain. The animation rig allowed animators to squash and stretch the eye while keeping the pupil and iris in perfect round shapes. developed as a set of on/off ramps to the high- way that is the studio’s legacy pipeline. “Our communication in and out was just caches,” he says. “That way, we could do pretty much what we wanted without worrying about complying with the pipeline.” Road to Rio Systems such as that made it possible to bring Rio alive. “The task was larger than we expect- ed,” Saldanha says. “We had a crowded beach. We had a parade with thousands of people partying. The animators had a list of I don’t know how many cycles. I was impressed with the work the crew put into it. It felt like we were shooting live action in Rio.” Modelers working from true topology and maps simplified the landscape to include the main landmarks and then built the city with a combination of procedural tools and hand- built models. “I wanted the city to look from afar like you’re there,” Saldanha says. To add such details as a mosaic-tiled side- walk on the Copacabana Beach, the materials artists again used procedural techniques rather than texture maps. “It’s harder than making something organic,” Hill says. “We had to fit together little black-and-white tiles into an in- tentional pattern. Procedurally generating that to the degree of handmade-ness that Carlos [Saldanha] wanted was difficult.” In fact, it took a collaborative effort between R&D, effects, and the materials department to create a method that worked. “Imagine a curvy spline in the middle of a box, with every- thing to the left black and to the right white,” Hill says. “We fed a series of these curves and random tile shapes into a stacking algorithm one of our effects TDs wrote. It fit the tiles to- gether like a puzzle, keeping the least amount of grout between.” The same technique paved the streets with cobblestones. 16 April 2011 The team also developed procedural meth- ods for the forests and jungles. “We couldn’t use displacement to create trees at a distance because the RAM footprint would have been too much,” Hill says. “But we wanted that de- gree of detail. So R&D and the materials art- ists came up with an implicit surface function that created tiny implicit surfaces shaped like trees.” Procedural rules dictated that the plants would grow only on horizontal surfaces, and various parameters controlled frequency and scale. “We could sprinkle trees all over Rio with no RAM footprint at all,” Hill says. “But in the extreme foreground, the procedural modeling crew did all the work.” Similarly, the water washing onto the beach combined procedurally animated materials and particle effects. “Most of the shots were fairly far away, so we didn’t have to create super-close waves,” Cavaleri says. “The crowds, though, were an enormous task. It takes so much ef- fort across so many departments to get the data to a reasonable number, and a lot of up-front homework to pull together the assets, place the performance cycles, and pass them through the Maya pipeline into our renderer in an ef- ficient way. And then, we needed a variety of techniques to render everything efficiently. We heavily leveraged our voxel technique.” A crowd of approximately 50,000 people enter the stands of the Sambadrome, and then the parade-goers march through. “There are maybe 100 on floats, and we had 10 or 12 floats, and then of course we had parade-goers in between separated by costume and color,” Cavaleri says. “They could be guys wearing alligator costumes, people on stilts with palm trees. We had amazing costumes.” The crew stored animation cycles for each dance in containers that included three to five cycles. For many of the costumes, each cycle went through a simulation pass. entire landscapes, the crew relied on a propri- etary voxel system developed by Maurice Van Swaaij. “We project a kind of camera-space voxel grid over a scene, cut up everything into voxel-sized pieces, and filter into each voxel,” Maurer says. “Instead of the raytracer tracking to hairs or leaves, it tracks to a voxel body. For fur, we’d store the average orientation, color, and density in each voxel. For geometry, we store the average normal. In addition, for this show, we started to voxelize material proper- ties, specular, roughness, and transmittance.” The voxel rendering method provided two advantages in particular: pre-filtering and RAM efficiency. “When we’re filling those voxels, we might have part of a hair land in one voxel and part in another, for example,” Maurer says. “So we end up with a 3D voxel body without abrupt changes from voxel to voxel.” As for RAM efficiency, Maurer points to shots in the Sambadrome. “With a raytracer, you need everything in RAM all the time,” he says. “It isn’t like [Pixar’s] RenderMan where you can break up a scene into parts and deal with packets. So, 30,000 characters would need 30g of RAM or more for a scene, and we had an 8g RAM budget per frame. By pre-processing all that data into a voxel body, we reduced the RAM to 5 or 6 gigs, and the rendering wasn’t noisy. The trade-off was the pre-processing time, so we’re always balancing that.” Composi- tors working in The Foundry’s Nuke assembled layers of the parade rendered independently. The last scene to wind its way through ren- dering and into compositing was a romantic sequence. “The two birds are beginning to fall in love,” Saldanha says. “The scene takes place in a mountainy neighborhood with stone streets. There’s a trolley and petals flying around. It’s a super-expensive sequence to put together, and I was biting my nails, afraid it wouldn’t happen. But, it was worth the wait.” Saldanha, who had held his passion for Rio and Rio at bay since 2002, could well have said that about the entire film. Rio marks a transition for the crew, too. “We moved forward on so many fronts, so many areas of new technology,” Burr says. “It’s the biggest step this studio has taken in terms of movies.” And the crew promises that this is only the first. n Barbara Robertson is an award- winning writer and a contributing editor for . She can be reached at BarbaraRR@comcast.net. Use your smartphone to access related videos. Computer Graphics W orld