Computer Graphics World

July 2009 53 CG I n n n n says. "is saves render time and reduces chattering because no particle or hair is ever smaller than a single pixel." e other technical advance for this show centered on lava, which flows in the new, lost world. "We collaborated with the materials and R&D departments to come up with an efficient way to visualize the flow of lava and add displacements," says Garfield. "e lava is a thin layer of par- ticles that ride along a surface." Ayala explains: "e particle-simulation engine is exactly like other particle-based simulation engines; however, this solver is designed to work primarily along surfaces and requires no settling period. It takes in a description of the lava surface and computes a plausible configuration for an already settled flow in a few seconds." is means the TDs have more time to experiment. e R&D department also helped the modelers create the lost world. "We built plant geometry using the fur-grooming system," says Maurice van Swaaij, R&D manager. "Instead of having modelers build plants, we generated them proce- durally. It was as if you were to take a big field and put hair on it, and then deform the hairs." Double the Fun Although this is the first stereo 3D film for Blue Sky, the challenges were more creative and workflow-related than technical. "We couldn't cheat the effects in space like we have done in mono films," Garfield says. "It was also important to allow extra screen space for the second eye, to make sure the effects have coverage." Similarly, the animators had to be mind- ful of cheats that they used to do. "If we have one character far in the distance and another close, when they tilt their head in 2D, they'd be looking at each other," Ga- bor says. "at wouldn't fly in 3D." e animators didn't work in 3D but could quality-check their shots to deter- mine if they were accurate or not. "It took a little getting used to at the beginning, but it wasn't a big leap," Dastrup says. "We got a feel for it after the first couple of sequenc- es went through the pipe. It's a popcorn movie, so lots of sequences have a roller- coaster type of experience. We stayed away from the gags, but we took advantage of stereo to amp up the fun and energy." Because stereo was new to the studio, the crew spent time assessing workflow is- sues, deciding whether to render one frame at a time or two frames at once, and con- sidering the ideal distances for the cameras. "We considered how young of a person we wanted to go to the movie and not get nauseous," van Swaaij says, "and decided to use the smallest distance for the smallest viewer. en, we needed to decide how big the theaters were. We could make a stereo set that looked great on a small screen but would cause trouble on a big screen. e worst case is a very young kid in a gigantic theater, so that's what we had to deal with. I pooh-poohed all this stuff in the first place, thinking, 'Do I really care?' Stereo never worked for me. But we found a method that worked, and I see stereo pretty well. And, yes, I do care." To create the stereo version, Blue Sky had a special stereo team with both artists and technicians who started with a ren- dered right eye and created the depth ef- fect by moving the camera for the left eye. "Deciding how much depth on a per-shot basis was an extra step," van Swaaij says. "But the stereo works great." For Saldanha, the goal was to have the stereo bring the audience closer to the characters and to the world. "We avoided poking the audience in the eye," he says. "We paid a lot of attention to character placement. We didn't want the movie to feel gimmicky. But, we have some amaz- ing stereoscopic action sequences that feel three-dimensional and fun." Saldanha has been at Blue Sky for 15 years now, and directed or co-directed all three Ice Age films, so for him, the ex- perience is as much a family affair as the story. "I knew pretty much everyone on the team," he says. "And the characters are my children. I love them all. So it was a feeling like meeting my family again. We have evolved so much, we keep finding ways to enrich the experience yet keep the essence of the characters and still satisfy the audience with something new, not just a sequel. It's a brand-new movie with characters you love." n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. Blue Sky's flexible rigging system helped animators accent Scratte's dual personality with body shapes that ranged from seductive to innocent.

• Cover