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Issue: Volume: 27 Issue: 11 (November 2004)

Hero Animation


This month, Disney/Pixar releases The Incredibles, the sixth animated feature film from the now famously dueling duo that has been rolling out box-office blockbusters since Toy Story, the first-ever CG feature, in 1995. Pixar's first PG film, The Incredibles has an edgier look and attitude than the studio's previous films.

Directed by Brad Bird of Iron Giant fame, The Incredibles features the voices of Craig T. Nelson and Holly Hunter as Bob and Helen Parr (Mr. and Mrs. Incredible), and Spencer Fox and Sarah Vowell as their children Dash and Violet—a family of suburban superheroes who have been hiding their superpowers. That's not the case at Pixar, where a crew of around 200 superheroes created the legendary studio's longest, at 107 minutes, and, they claim, largest film yet.





By comparison, while Disney/Pixar's Monsters, Inc. had 1400 shots, The Incredibles has 2253. "I set out to tell the story the best way I could, and Pixar wanted the same thing," says Bird, who transferred his talents to the studio in 2000 after making Iron Giant at Warner Bros. "Pixar doesn't waste money, but they're not about saving money. They want the money to be well spent. They're motivated to make a great film."

Another benchmark: Monsters, Inc. had 56 master lighting set-ups, while The Incredibles has 179—from jungle islands to suburbia. The film has smoke, fire, ice, missiles, cars, trucks, airplanes. The characters swim underwater, fly through the sky, explore caves, go to school. In addition to the Incredible family, the film features eight other main characters in various costumes. Their hair styles range from a classic comb-over to a buzz cut to hair long enough to hide behind.

To achieve the supersized scope of this animated action-adventure film, two elements worked together. Bird's unique approach to animated filmmaking made it possible for Pixar to apply techniques more often used in live-action films than animations. And, the studio developed new methods for managing the complexities of animating multiple humans with simulated muscle deformations and dynamic clothes and hair.

Many animation directors use storyboards primarily to show dialog—to illustrate and work out the story. Separately, a layout department creates camera moves. But, Bird's storyboards for The Incredibles included camera moves. "It's not about dialog. It's about the movie," says John Walker, producer. "When Dash has a 100-mile-an-hour action sequence, people get the cinematic punch."

Walker traveled with Bird from Iron Giant to The Incredibles. "They sort of wrapped us in bubble wrap when we got here," he says, "and made sure the A-team surrounded us."

One member of that A-team was Rick Sayre, supervising technical director for The Incredibles, his fourth film at Pixar. "Brad's storyboard was more like a live-action storyboard," says Sayre. "It was 2D, but it was created in [Adobe's] After Effects—it had the timing, the pacing, the camera moves."

The crew borrowed other tricks from live-action filmmaking as well. When characters performing inside a building did not react to action outside a window, for example, the equivalent of a first unit crew (the animators) worked on the characters' performances and a second unit worked separately on the outside scene. "It was as if the characters were on a greenscreen stage," says Sayre.

For some of those backgrounds, the crew even used 2½D matte paintings. "The second unit created 'digimattes' using 3ds max and Brazil," says Sayre, referring to Discreet's 3D software program and SplutterFish's rendering software. "It was great fun, ... liberating."
For ex-superheroes Bob and Helen Parr, life in suburbia is a stretch. So, the former Mr. Incredible and Elasti-Girl lift their spirits as best they can. New rigging technology from Pixar made Helen's elasticity possible.




Virtually every type of natural phenomena appears in the film at least once, according to Sayre, from fire to fog. Most were created with computer graphics, but not all. One example: "When the baby is in the sink, we used a live-action water splash filmed in a kiddy pool," he says.

Even the lighters used live-action elements. Filmmakers put "cookies" or "cucaloris," which are patterns cut out of wood or another material, in front of a light source to create shadow patterns. Similarly, Pixar's lighters used cookies rather than geometry and shaders to create shadow patterns for the film. "We bought silk plants, projected light through them onto translucent fabric, and filmed the shadows," says Janet Lucroy, director of photography. "We used these shadows all over the place. For example, when Bob and Helen say good-bye at the front door, we created the tree shadow that you see on the house without having to build a tree."

The lighters worked interactively with shadows created from these virtual cookies thanks to a proprietary, real-time lighting tool. "It brought us closer to live-action lighting," says Lucroy. "Before, we had to place a light, render a scene, see if the falloff was where we wanted, move the light, re-render. Now, we can compose with shadows as well as with lights."

To create soft shadows, the lighters used ambient occlusion judiciously. "We used it where we got the most bang for the buck," says Lucroy. "We can fake the shadows for a painting on the wall, but when Helen puts her hand on Bob's arm, we get a lot of payoff." For rendering, the team used Pixar's commercial RenderMan software, PRMan Version 11.5, according to Dana Batali, director of RenderMan product development. "But, because they're in-house, they also had access to features that are just coming out now in Version 12," he says.
Enhancements to Pixar's proprietary simulation engine allowed technical directors to sculpt the rest behavior of hair as well as change its dynamics. Simulated hair could be moved into keyframed shapes.




The important issues with the characters in The Incredibles were that there were many of them, they were humans, they had bizarre shapes, and they could move, squash, and stretch in unreal ways. The crew had to do cloth simulation, hair simulation, and muscle simulation on at least one and often multiple characters in every shot.

"We had two opposing ideas," says Bill Wise, character supervisor. "The characters were stylized cartoons that had to be believable humans. With our kind of faux realism, the closer you get to real, the creepier."

Rather than start with sculptures, modelers working in Alias's Maya created the stylized shapes from scratch in the computer. For articulation, Pixar uses its own system. "Rigging these characters was a challenge," says Wise. "There are a lot of them, and they're superheroes. So, they have to perform in wild extremes, and we needed to see muscles—to see Bob's chest expand and his biceps flex."

The crew had one advantage: All the characters, with the exception of a recalcitrant feline, were bipeds with a similar structure. Thus, the tools group developed technology that allowed rigs, built by the character team, to be reusable. "Every character referenced a template rig," says Wise. "A change to the template would propagate to all the characters." In addition to basic joint rotations, the rig handled extreme stretching—especially for Helen's elastic arms—and squashing. "We compress, squash, distort Bob like crazy," says Wise. "In this film, when a character leaps back, we wanted a cartoony arc."

In addition, the super characters needed dynamic muscles, a new requirement for Pixar. In a typical 3D pipeline, animators perform a character by manipulating a skeleton, and then a technical crew attaches muscles to the bones and runs a muscle simulation. The bones move the muscles and the muscles drag the skin along. But, any automatic muscle movement worried Pixar's animators at first.

"The traditional techniques had everyone scared," says Sayre. "The animators did not want to give up control of the silhouette. So, John Anderson and the tools group made it possible to use physically based technology with high-level controls."

Wise's character group built reference muscles—deformer objects attached to bones at two points—and put each character through a set of training drills that exercised the degrees of freedom for each character's joints. The attached muscles moved accordingly.
Director Brad Bird provided the voice for Edna, shown here with Bob. By using statistical modeling for cloth and muscles, Pixar's Studio Tools helped animators see the characters' outlines.




"We baked the muscles and created a statistical model," says Anderson. "We ran the training set into the baked muscles and calculated the internal coefficients." Thus, even though the animators weren't manipulating muscles, when they posed a character, an algorithm could quickly evaluate the model and wrap it with skin shaped as if an underlying muscle had moved. In other words, Sayre explains, "We trained it to know that when a character looks like this, the muscles look like that. We had dynamics without running dynamics." As a result, the animators could see the silhouette.

Pixar then applied the same technique to clothes. First, a technical team assembled costumes in Maya and then tested the costumes' behavior on animated characters using Pixar's proprietary simulation engine to move the cloth.

Pixar's computer scientists David Baraff, Michael Kass, and Andy Witkin created the patented technology for Sully's fur and Boo's T-shirt in Monsters, Inc. The Incredibles had more characters with clothes and tougher problems. "What's hard is when cloth moves slowly and when it collides against something small," says Anderson, noting that in one scene Bob puts his hand through a tear in his super suit. "Collisions with fingers don't work well because the cloth is the same resolution as the finger, and it snags," he says.

The breakthrough in handling cloth simulation for multiple characters was in applying a statistical model. "Statistical cloth let us cross off a lot of shots," says Anderson. "We trained the statistical model of the baked cloth using the set of training poses; the compressed memory of what the cloth looked like in those poses was implemented in an algorithm." That meant, as with the muscle system, based on a training set of poses, Pixar got a full cloth simulation for a performance without running a simulation for that specific performance.

When the technical crew for Monsters, Inc. first saw Boo, she had bangs that brushed her forehead. They persuaded director Pete Docter to give her ponytails instead. The crew wasn't as lucky with The Incredibles—especially with Violet. "Violet is an unsure teenage girl," says Sayre. "She hides behind her long hair." Anderson, Witkin, Baraff, and Kass evolved the core simulation engine to handle additional collisions caused with long hair and keep the movement flowing properly.

"For Violet, Brad specifically wanted her hair to be part of her performance," says Wise. "She puts her hair behind her ears, runs her hands through her hair." These everyday human movements are among the most difficult to simulate.

"You can't simulate the contact of every hair, so you work with clumps," says Anderson, "but when you apply the properties to all the hair, it tends to lose coherence, so we spent a lot of time increasing the coherence of motion."
Clockwise from top left: Statistical models made it possible for animators to see how a squashed and stretched character's skin would look. Once animated, the characters are placed in their 3D environment. Hair and complete costumes are then added, and th




Besides working on the core simulation engine, the engineers added features that give technical directors more control. "TDs could adjust the position and velocity of the hair, put forces on it, keyframe a pose that would attract the hair, and sculpt rest behavior into hair," says Anderson.

The simulated hair was rendered with dense shadows to separate the strands, but that caused problems when, for example, it cast a shadow on a character's face. "The characters were rendered with translucency unless they were very graphic, but translucency in the hair didn't work," says Lucroy. Extra fill lights fixed that problem.

The optional subsurface scattering, which gives characters' skin a more natural look by bouncing light through layers of virtual skin, gave the primary characters translucent skin as needed. "They had to feel alive, but we couldn't use 30-micron scans of someone's face to create pores and pimples," says Sayre.

Adds Bird, "CG looks plastic without detail, but the goal was not to create lifelike humans. We had stylized, deformed people. So there was a fine line between creating creepy animated dead people and plastic characters. We hit a sweet spot by using less detail and more subsurface scattering."

As always, Pixar has advanced the art and the technology of filmmaking—this time, with Brad Bird's prompting, in new directions. "We had a motto," says Sayre, who describes his job as running shotgun for Bird. "Welcome to The Incredibles. We're still figuring things out."

Barbara Robertson is an award-winning journalist and a contributing editor for Computer Graphics World.
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