Computer Graphics World

September 2009 16 n n n n CG I•Stereo concept drive everything without, neces- sarily, stretching limbs and body parts. e main character Flint, for example, who is skinny, awkward, and nerdy, has hoses for arms. No elbows or knees. "He was a loose, gangly character," Nash says, "so it made sense not to give him a skel- eton in some cases. But we still kept him grounded." For example, when Flint walks, he often doesn't move up and down; he moves in a straight line, with only his legs animating. at bolstered the concept of an intensely focused inventor, and it fit with the UPA style of animation. "When a UPA character walks into a room," Nash says, "the upper half might lock [while] the lower half keeps walking, and then the upper half would catch up. So, with our rig, animators could change pro- portions and lock parts of the body so those parts couldn't move when others did. For example, we could put the chest in world space or in body space, and then switch back." With that kind of control, the ani- mators could have Flint and the other char- acters sometimes act in this unique style and still have seamless performances." By contrast, the animators created a real- istic performance with accurate mechanics and follow-through for the self-important Brent, the town's only celebrity, albeit a performance they still sometimes exag- gerated. Earl, the town's cop, on the other hand, moves in more extreme ways. He is an incredible athlete with nothing to do, so he overstates everything physically. "When he moves, it's like a sprinter explod- ing off the blocks, and he stops on a dime," Nash says. "He does that even when it's not n ecessary. He'll do a flip and two somer- saults, and land just before telling someone they got a parking ticket. I loved [this style of animation]. e very idea of concept driv- ing everything is, to me, what animation is all about. It's the reason to animate a movie instead of doing it live action." In addition to creating performances, the animators also sometimes created char- acters using the flexible rig to transform a generic model into a specific secondary character. "e directors wanted 80 char- acters," Bredow says. "It wasn't feasible to build that many modeled, rigged, textured characters in time, so we came up with a clever compromise." Modelers built the 30 hero characters, which could morph into new characters, and added a generic male and a generic female to the digital crew list. "We could change their proportions, skin color, costume, lots of things about them to create a rich set of background characters who could deliver lines at cam- era," Bredow says. "Pete [Nash] and his team created characters on the fly as need- ed from artwork and inspiration." Imageworks' proprietary crowd system provided the means to control large num- bers of characters when needed. "It's basi- cally a [Side Effects] Houdini-based system that allows you to place characters, bring in motion libraries, and choose what executes when and where," says Dave Davies, effects animation lead. "It uses goals and steering behavior to get characters from one place to another." Chewandswallow e characters populated the town of Che- wandswallow, as in the book, so for the film, modelers built a city 14 blocks long from east to west and 22 blocks long from north to south, with eight buildings on each block. Four times. "e modelers built this huge town, where pretty much every street was shootable for wide, medium, and close-up shots, and then in the second act, the mayor takes out a loan and converts it into a food utopia," says Bre- dow. "So we built a second town. And then the food falls, so we rebuilt the town with a food layer. And then, it's destroyed." Although texture maps handled some variations, for the most part, modelers created each version anew, including all the props that dressed the set—cars, street lamps, trash cans, and so forth. In addition, the modelers added items for the interiors Layout artists "filmed" about 20 percent of the colorful film using a handheld camera to compose the CG scenes.

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