The Sky's the Limit
Issue: Volume: 28 Issue: 11 (November 2005)

The Sky's the Limit

Over a span of 77 years, Walt Disney Studios pioneered and perfected the relatively young art form of hand-drawn animation. From squash and stretch and overlapping and secondary action, to slow in and slow out, Disney founded the fundamental principles of animation and became home to the most talented artists in the world. Collectively, these artists have made the studio the gold standard in traditional feature animation and the icon of quality family entertainment.

By the turn of the century, however, Disney, in partnership with Pixar Animation Studios, was producing 3D films that widely outperformed its hand-drawn movies at the box office. Thus, when Pixar decided to secede from the alliance following the release of The Incredibles (see “Hero Animation,” November 2004, pg. 18), Disney chose to adapt the talent of its “Grade-A” 2D animators to the digital realm. This month, Disney’s decades-old legacy will be carried into this frontier on the wings of Chicken Little, the studio’s first solo foray into all-3D features.

“Finally, we were able to put these amazing 3D tools into the hands of the greatest painters, animators, and effects artists in the world,” says Chicken Little’s visual effects supervisor Steve Goldberg.

For Chicken Little, its first all-3D feature film without partner Pixar, Disney hatched a new CG animation approach that is based on its tried-and-true traditional techniques.
Images © 2005 Disney.

Far from abandoning its hand-drawn roots or copying Pixar’s aesthetic, Disney’s mandate for Chicken Little was to stand on the shoulders of its 2D heritage and capture, through the same use of squash and stretch, staging, and theatrical lighting, the spirit of animation as seen in films such as Peter Pan and Alice in Wonderland, and especially the wild, fluid motion of the 1942 Goofy cartoon “How to Play Baseball.”

In the works for more than five years, Chicken Little was conceived while director Mark Dindal was trying to apply real-world logic and human motivation to his favorite children’s stories, a process that spun the tales into interesting and often humorous directions. “I always thought it would be fun to ask questions like, Why would this character do that? In ‘Little Red Riding Hood,’ for example, the wolf could eat the girl when he first meets her, but instead takes this long detour and disguises himself as her grandmother,” he says. “Suddenly, the characters become more interesting and complicated.”

While toying with this concept, Dindal was developing another, separate idea about misfit farm animals that get left behind when all the pretty animals are off being judged at the county fair. While they’re away, aliens invade the planet, leaving the misfits to save the world. “One night, these two ideas merge and solidified into Chicken Little,” says Dindal.

The film begins one year after Chicken Little was conked on the head by a falling acorn, only to proclaim the sky was falling, causing panic in his town of Oakey Oaks and shattering his father’s faith in him. Now an outcast, the bird tries to redeem himself and regain the respect of his father, Buck Cluck, by joining the local baseball team. After leading the town team to an upset, he is conked on the head yet again-this time by a chunk of UFO.

Afraid of losing his newly rehabilitated reputation and the hard-won respect of his dad, Chicken Little remains mum about the incident. Instead, he enlists his misfit friends-Runt of the Litter, a timid 400-pound pig; Abby Mallard, an ugly duckling; and Fish Out of Water, a wide-eyed exchange student from the ocean-to return a missing alien child named Kirby to its parents and save Oakey Oaks from an alien “coop d’etat.”

Disney modeled and animated Chicken Little and his misfit friends using Alias’s Maya, employing the same “roundness” in their designs that can be found in early Disney movies.

To visualize this story, Disney selected 50 percent of its new CG animation team from the traditional ranks, and put them through a rigorous 18-month training program, which included an introductory to Alias’s Maya, the main 3D commercial software used by the studio on the project. Despite the intensive 3D education, the underlying technological focus of the production was preserving the quality of hand-drawn animation and ensuring that no limitations were placed on the artists’ ability to apply those techniques in the digital medium. Shouldering this responsibility was an enormous challenge for Goldberg and his team because Dindal wanted the animators to push the principles of animation to extremes.

In the same spirit as the Goofy cartoon, the animators infused the characters with broad caricatured movements rarely seen in CG films. For instance, during Chicken Little’s baseball game, the windup and delivery of the stork pitcher boasts a level of cartoon exaggeration that belies the puppet-like, or mannequin-like, feel normally associated with even the best CGI. When a groundhog slides into second base, his cheeks flap around wildly, buffeted by g-force winds.

Bringing this hand-drawn feel to CG required a tool that could provide a seemingly endless variety of unique shapes for the characters. To accomplish this, Disney created a collection of wire deformers that allowed the animators to pull out variations on the blend shapes already defined by the rigging department.

Dindal also directed the filmmakers to seek the same “roundness” in the character designs and animations as seen in the Disney films from the ’40s and ’50s. This rounded aesthetic also extends to the designs of the Oakey Oaks set, where bulls own the china shop, penguins operate the tuxedo shop, and worms run the bookstore. The off-kilter architecture of Oakey Oaks is always curving and whimsical, devoid of straight and parallel lines, right angles, and concentric circles. Nothing is symmetrical.

Oakey Oaks was divided into a number of “locations,” such as the town square and Cluck Street, where Chicken Little resides. Layout artists then divided these locations into “sets,” which comprise a particular side of a street and all the individual storefronts lining it, and drew upon a library of stock buildings to furnish those locales. “We created ‘look variants,’ which basically altered the shader parameters of the same building,” says Goldberg. “If you look closely, we had some shots with a couple of fire stations.”

All the image phases from the layout to the final frame were done digitally in Maya. This series of stills (from top left) shows the progression of imagery leading to the completed frame: scene layout, animation, lighting, visual effects, and the final sh

With the story line constantly evolving, layout artists built the town square to hold up in medium shots, adding detail as the story was finalized. While digital matte paintings were used sparingly, artists occasionally rendered out elements, such as trees and the baseball diamond, and retouched them in Adobe’s Photoshop for use as background cards.

Dindal also tried to emulate the staging, color, and lighting of legendary Disney artist Mary Blair and the films she influenced, such as Peter Pan. Studying the way she staged action and used theatrical pools of light to guide the viewer’s eye, the artists designed Chicken Little’s shots so that the characters would appear light over dark or dark over light. “Sometimes we’d create complex, fake shadows, or come up with something just off screen to justify the shadow,” says Goldberg.

To light the sets, the artists used Disney’s Lumiere, which plugs into Alias’s Maya and feeds into Pixar’s RenderMan. Partly Mel-scripted, Lumiere’s interface facilitates the automatic propagation of lighting rigs throughout similar shots, and uses standard keys, fills, and bounces.

Disney employed a curved, whimsical design aesthetic to the film’s environments that is apparent in this view of the buildings and objects in the Oakey Oaks town square.

In addition to using geometry and virtual lights to create shadows, the lighters often projected real light through actual materials and filmed the shadow patterns, creating cookies, or “cucaloris.” These filmed shadows are most noticeable during a flashback to the day when Chicken Little, seated beneath an oak tree, is first struck on the head. Artists used these cookies to create the soft shadows from the dappled lighting filtering through the tree canopy.

Hand modeling all the characters in Maya using subdivision surfaces, the artists created Chicken Little with 5636 polygons, Runt of the Litter with 6627, and Abby Mallard with 12,781, half of which reside in her hair alone. Like most of the characters, Chicken Little’s body comprises separate pieces of unattached geometry. For example, his arms were not connected to his body, nor were his hands connected to his arms; instead, they were bound to the body with joints hidden under his sleeves.

“This simplified the animation process,” says supervising animator Jason Ryan. “I could rotate his hands and arms two million degrees and not have things get twisted up.”

For the facial animation, the artists created a set of basic blend shapes in Maya. Over these, they added a series of wire deformers called Chicken Wire, allowing the animators to tweak the basic shapes into any facial pose they desired. “We’d have blend shapes to get us 80 percent there, then we’d use the Chicken Wire controls along the upper beak, lower beak, or on the brows to shape and tweak them, and get a nice graphic for the camera angle we were animating to,” explains Ryan.

Unlike traditional wire deformers, which can only be translated, the clusters along Disney’s Chicken Wire-called Chick Clusters-can be scaled, translated, and rotated. Audiences can see the Chicken Wire effects most prominently on Buck Cluck, as they added great subtlety to his facial movements. With Chicken Little, on the other hand, Ryan went very broad with his animation, using a lot of squash and stretch and relying less heavily on the deformers.

Using bones and IK handles in Maya, the artists rigged the characters with a “broken” rig setup, allowing them to translate any portion of the rig without affecting the rest of the skeleton. “The animators could select the hip bones and translate them 20 feet away, and it wouldn’t affect where the chest, shoulders, head, or feet were,” explains Ryan. “This provided a lot of flexibility for squash and stretch.”

Still, each character’s performance posed its own challenges. For example, the skittish Runt of the Litter is a huge mass carried by dainty legs that take tiny, fear-ridden steps. “When he came to a curb, he would actually have to stop, anticipate, and jump up. He took everything very carefully, except when he got scared, whereupon he would just take off,” says Ryan. “We weighted him so that his bottom half would drag his top half. This meant his little legs would start running, but his top half would drag behind a little bit. And when he stops, he would follow through a little, instead of just stopping on a dime like Chicken Little.”

In making the transition to 3D, Ryan, a former 2D animator, developed a method of working that shortened the learning curve for the other traditional animators. “Because computers aren’t real time yet, we needed something intuitive and familiar, so I would start working on a Wacom tablet PC, just trying to solve the performance with some rough drawings. Once the director liked the performance, I would then use Maya as my cleanup tool, posing the skeleton to match the poses I had drawn on the tablet.” That approach proved so successful that all the 2D animators were given Wacom tablets running Disney’s Show Tool software for sketching out their animations and perfecting the animation timing.

“I went from doing 3 or 4 feet per week on Dinosaur to over 16 feet a week on Chicken Little,” adds Ryan, referring to Disney’s 3D film that used photographic backgrounds (see “Beauty...and the Beasts,” May 2000, pg. 22).

A tool called Shelf Control-akin to a Fisher-Price version of Maya’s Hypergraph-simplified the selection of character geometry and rigging. Instead of a node tree, the animators would see a flattened-out character, and by selecting the head, fingers, or other body parts, they could choose the corresponding joint on the model. Meanwhile, Disney’s Timing Chart replicated the charts that 2D animators are accustomed to using for their keyframes.

As a matter of fact, capturing the snappy, energetic feel of traditional 2D animation demanded a lot of keyframing. “There was almost a key on every frame; very little was left to the computer,” notes Ryan. “In contrast, on Dinosaur, we’d have a key at Frame 1 and a key at Frame 9, and let the spline do the rest.” So that the animators could define a character’s silhouette as precisely as they would in 2D, the artists applied numerous influence objects (which were more predictable) and added Maya’s sculpt deformers to the Chicken Wire deformers.

The artists had difficulty expressing Chicken Little’s emotions, since his black eyes are devoid of pupils. To overcome this, they would turn his head around to convey an eye direction and thought process.

Smear frames, in which a character’s face stretches out during a fast head turn, for example, were also accomplished using influence objects and Maya’s sculpt deformers. “We’d fatten out the face for one or two frames, just to add a little more fleshiness to the character,” explains Ryan. In fact, the animators limited most of the extreme squashing and stretching to a few frames, to add a sense of elasticity and yet eliminate the “rubbery” look.

Because of the extreme elasticity of the characters, Goldberg’s job was to ensure that the mesh held up during later stations in the pipeline and that the fur solution supported the squash and stretch. This would prevent the fur and feathers from thinning out or compressing unnaturally during deformation.

Disney’s proprietary fur tool, XGen, received a full rewrite when Disney made the leap from NURBS to subdivision surfaces following the completion of Dinosaur. As a result of the tool, Chicken Little sports more than 76,000 individual feathers; 55,000 of those are on his head, while 9000 adorn each arm. Using guide splines and a host of channels for mapping color, density, and other properties, XGen produced all types of feathers and fur-from long, traditional feathers to small, fluffy, down-like feathers, and even the long spikes of Morcupine Porcupine.

During gym class, a bully pulls Chicken Little’s comb back like a slingshot and catapults him into a window; as he slides down the glass, he grabs hold of the fire alarm, setting off the sprinklers. To slowly turn Chicken Little’s dry feathering into a bedraggled mess for this scene, the artists applied displacement maps and adjusted such properties as specularity and clumpiness within Disney’s XGen fur tool.

Nevertheless, in an effort to re-create the stylized cartoony splashes they were accustomed to creating in 2D, the traditional animators often sought out novel approaches to fluid simulation.

For instance, when Chicken Little is training to make the baseball team, he runs alongside Fish Out of Water, who gives him what he thinks is a squirt from a water bottle. When he realizes the water came from Fish’s aquarium-like helmet, he does a “spit take.” In another scene, Chicken Little is doused with Gatorade after making the game-winning hit. Animating these fluid effects was Peter De Mund, a traditional animator who, like half of the effects department, was making the crossover to CG.

“De Mund took the approach that he would have taken in 2D, but applied it to 3D,” says VFX supervisor Steve Goldberg. “He essentially sculpted chunks of geometry frame by frame to get the designs he wanted, producing exquisite cartoony drips and splashes. This didn’t seem like a crazy idea to him, because he used to have to draw all these little water droplets in 2D. It sounded crazy to us, before we realized he was plowing through it much faster than most people would have taken to render and repeatedly tweak the simulation.”

Like the character animators, De Mund also used Disney’s Show Tool and a Wacom tablet PC to rough out the fluid animation in 2D before re-creating it in 3D.

Later in the film, when fluid effects become more abundant, effects supervisor Dale Mayeda introduced Next Limit’s RealFlow into the production. For complicated effects, the artists combined De Mund’s handcrafted fluid animation techniques with RealFlow’s simulation. - MM

For the character facial animation in Chicken Little, the artists used wire deformers, called Chicken Wire, that enabled them to tweak a basic set of blend shapes into just about any facial pose they needed.

For complicated collisions between the fur and the geometry, such as when Chicken Little runs his hand through his hair, the animation department collaborated closely with the Character Finaling department, which was responsible for cleaning up self-intersections, pinching, or other defects following the animation.

After progressing through the Character Finaling department, the animations were sent to the effects department. There, effects animator Rob Rosenblum created a proprietary wind-simulation tool within XGen that applied a set of forces to the fur and feathers. This is most noticeable during the climax, when the heroes stand atop a building to deliver Kirby as the mothership looms overhead, and the rising wind ripples their plumage violently.

Once the dynamic simulations were added in the effects department, the Shot Finaling department composited the scenes in Apple’s Shake and rendered them in RenderMan via MTOR, a Maya-to-RenderMan file converter.

Chicken Little represents a new day for Disney, and will be used by critics and industry experts to evaluate the future of the company in the vanguard of CG feature animation, which is currently held by Pixar and DreamWorks. The film not only represents a new beginning for many traditional animators, but also an unprecedented collision between the worlds of 2D and 3D animation.

Chicken Little was such a breakthrough picture for so many artists,” says Ryan. “That’s because a lot of the CG crew had never animated cartoony, character-driven stories, while the 2D crew had no CG experience. They really helped each other.”

Now hard at work on its next feature-length film, A Day with Wilbur Robinson, Disney is continuing this unique marriage of disparate talents-a plan that just may result in some new Disney “classics.”

Martin McEachern is an award-winning writer and a contributing editor for Computer Graphics World. He can be reached at