Cloth, too, was such a vital component that, for Rio, Blue Sky created a department strictly devoted to cloth and sim with a dozen artists so they could handle the demands of the Carnival parade. There are 50,000 people for one pull out shot and it takes 3,000 fans to fill one set of bleachers. In addition, the fans consisted of 10 unique people, each able to do two different types of motion: "cheer" and "cheer crazy." Blue Sky was able to swap outfits on the people in the stands to help with variation (each one had about three or four different outfits). However, each section of the parade only had one costume type. Even the characters in the parade that are super close to camera were part of the crowd cycles.

"For crowds we created proprietary techniques that allowed us to pre-store information earlier so you didn't have to load it all into memory at the time of render," explains Cavaleri. "That was important because we had to find a way to produce all these crowd shots and, in some instances, we could layer the crowds together, but [not always]. So we came up with a way to calculate and pre-store a lot of information earlier and write it on a file system that allowed us to iterate quicker on the crowds and allow that complexity to be rendered. There's a shot in the parade reveal that to render a single frame of that crowd layer, which is basically the people in the stands, took about 65 hours and 6.6 gigs of RAM. And there were 2.2 billion rays that were fired in that particular layer.

"We found clever ways of getting more with less. Blue Sky generally does not use texture maps, so Linda's material was defined procedurally. She was produced with 10,764 lines of studio ++ script. And one dance costume has 24,000 procedurally created, hand-adjusted sequins."

But Simmons says "they're maxing out the current technology because that pull-out shot had 30 plus animation files, which is right back to where we were on Robots. So we're constantly trying and improve and look for new ways of handling these humongous scenes in future movies."

Blue Sky was also able to come up with some very unique tools using cloth technology for the chain that linked Blu and Jewel throughout the film. The tool was so robust that they were able to hand it to the animators and let them manage the interaction between Blu and Jewel. They were even able to direct the simulation, and only set keyframes when required to pass through a shape. "We knew we nailed it when the animators did a test and had Blu and Jewel jump through the air and the chain formed a heart and relaxed into a normal shape again," Cavaleri says. "And it looked completely natural and seamless."

Rio itself is like another character, which provided its own set of challenges. Blue Sky took some liberties, not surprisingly, and pulled in some of the beach shorelines and other key landmarks to stylize it just a bit. "And once we had the key landmarks identified, we constructed the buildings and actual town locations, the favelas and so forth," Cavaleri reveals. "And a lot of those buildings were set dressed procedurally with a tool that we created to fill in and block out city streets and put the road in between. But it was advantage using a known location. We also projected the imagery in Nuke onto geometry and that allowed us not to have to render the background in every single shot. You could even drift the camera on it."

Then there was the foliage, which had to be very detailed, especially the deciduous, small leaf trees. How to move the leaves on the trees to give the environments more life? This was a breakthrough. "Another was how to populate the hillsides in the vista views to construct that lush landscape," Cavaleri adds. "We ended up creating a new technology -- an advanced form of displacement -- that allowed us to achieve the lush looks. If you think about how a painter might just press the brush onto the canvas to create a splotch of paint that actually looks like a crop of trees. In a way, we were able to achieve the same result using this technique without having to instance and propagate hundreds of thousands of trees across the hillside."

Bill Desowitz is senior editor of AWN & VFXWorld.