With 12 human characters in starring roles, the Pixar team faced several "super" problems: They had to rig 3D characters, which had bizarre cartoon shapes and superhero powers, so that they could act like 2D characters. " [Director] Brad [Bird] wanted the puppets to move in hand-drawn ways, like traditional animation," says producer John Walker. They needed to make the characters look like believable humans despite their designs, which meant giving them realistic skin and muscles. They had to dress the characters – some even had costume changes- and give them hair. Think Sully and Boo of Monsters, Inc. multiplied by 12, and then extend that to fill a 107-minute film. As a result, many of the technical advances and new techniques were prompted by a need for efficiency – and art direction.
For hair, the advances were largely the addition of internal and external forces that helped technical directors control the simulation engine, originally developed by Pixar’s tools group for Monsters, Inc. The team could attract hair to a keyframe, sculpt rest behavior into hair, and change its dynamics. In addition, the technical gurus in the tools group worked on keeping hair coherent while it was moving.
To help speed character rigging, the tools group developed new technology that made it possible for the character group, which handled designs, models, rigging, clothes, hair, shaders, and textures, to build one re-usable rig for all the characters. The models were built in Maya, and the rigging, or the articulation, was added with Pixar’s proprietary software, which was enhanced to allow squashing and super-stretching (Helen is Elastigirl, after all). To simplify the rigging, the group had the characters all reference one template. "It could be applied quickly," says Bill Wise, character supervisor, "and a change to the template would propagate to all the characters. It has basic rotations at major joints, squash and stretch, and a muscle system on top."
"For the skin," Wise adds, "we had a sculpted shape that was sucked down onto the muscles. The bones moved the muscles and the skin dragged along, but we could let the skin slide or stick it down tightly." This description of the muscle-and-skin simulation process sounds like a typical visual effects pipeline where animators perform characters and then hand them to a technical crew that runs the sims. But Pixar isn’t typical.
Seeing More of the Character
The Incredibles was written and directed by Brad Bird, who joined Pixar in 2000 after directing The Iron Giant for Warner Bros. "The story is based on an idea I had in the mid-’90s," he says. "It’s about a guy who gives up what he loves and then resents it to the point that he doesn’t see what’s around him. It seems like a big goofy Hollywood movie, but I feel like it’s a personal film in pop clothing." That guy in the film is Bob Parr, aka Mr. Incredible, a former superhero who, along with his wife Helen (Elastigirl) and their super-children, Dash and Violet, has been reduced to living a normal suburban life, unable to use his superpowers- at least in public- for fear of lawsuits. One day, Bob gets a chance to don his super suit, and the story cranks up.
As in traditional animation, animators working on The Incredibles wanted to see the shape of the character, not just the character’s performance. "In our world, it’s important to see what the line of the character looks like," says John Anderson, a senior scientist in the studio tools group who joined Pixar after developing simulation engines at ILM. To be able to build skin over dynamic muscles quickly enough for the animators, Anderson and the tools group developed statistical models. "There has been a lot of research in statistical dynamics," Anderson says, "and our work fits into that body of research."
Essentially, they put a character through a set of exercises- a representative sample of poses – and then used the muscle positions for those poses to train a mathematical representation of the internal coefficients; they’d create a compressed memory of what the muscles looked liked and implement it as an algorithm. "The system would know that when a character looks like this, the muscles look like that," says Rick Sayre, supervising technical director. Thus, the animators could see the result of a dynamic muscle-and-skin system without running a simulation.
Then the tools group spun that idea into clothing. "We trained a statistical model of the cloth," says Anderson. An evolution of the simulation engine developed by Andy Witkin, David Baraff, and Michael Kass for Monsters, Inc. moved the cloth during the training exercise. Once trained, the statistical model took over. That made it possible not only to do cloth sims for multiple characters who appear throughout the film, but also to do so while giving animators control of each major character’s silhouette.
The use of statistical models is likely to be adopted by visual effects crews faced with similar problems, another way in which technology proven at Pixar might find broader use. But with The Incredibles, the movement of technology and technique from animation to live-action was a two-way street.
Bird developed storyboards with help from a team that used Adobe After Effects and, like visual effects animatics but unlike traditional animation, the initial storyboards included camera moves. This made it possible for the crew to adopt other live-action techniques- building only what the camera could see, for example. They also used live-action elements- splashes, shadows, and so forth – and 2 1/2-D matte paintings.
For the characters’ skin, the crew applied subsurface scattering, but not detailed texture maps. "We had stylized, deformed people," says Bird. "We didn’t want them to look plastic, but too much detail made them look creepy." For this film, Pixar relied on several commercial tools: Pixar’s PRMan 11.5 (with access to features now in 12), Alias Maya, Adobe AfterEffects and Photoshop, Apple Shake, and, for matte paintings, Discreet’s 3ds max and Splutterfish’s Brazil. A new, proprietary interactive lighting tool helped lighters balance the look. And, once again, the hardest technical problems the crew solved were those in which the technology is least evident. "When Helen pushes Violet’s hair behind her ear, when Bob puts his hand through a rip in his super suit, those are our triumphs," says Wise.