Building a Better Mouse

Talking to the digital wizards at Sony Pictures Imageworks about the 3-inch talking mouse who stars in Columbia Pictures’ holiday release “Stuart Little” can be a somewhat disorienting experience. The expected technical explanations of how the character was designed, animated and composited into a live-action film are frequently punctuated with references to Stuart as though he were an absent member of the family. In fact, that nearly tangible spirit of Stuart Little has so permeated the halls of the Culver City effects shop that one almost expects him to walk into the conference room and join the interview.

Based on E.B. White’s 1945 book “Stuart Little” and scheduled to open Dec. 17, the film tells the story of a human couple, played by Geena Davis and English comic actor Hugh Laurie, who adopt a child named Stuart who happens to be a mouse (Stuart’s voice is provided by Michael J. Fox). For director Rob Minkoff, one of the initial challenges was figuring out how to translate the off-kilter reality of White’s book to film.

“Stuart lives in a world where people aren’t surprised at his existence or shocked by the fact that he can talk,” says Minkoff, who is making his largely live-action debut with “Stuart Little,” having co-directed Disney’s 1994 mega-hit “The Lion King.” “There’s something slightly removed from our world, and yet the characters had to have recognizable emotions and feelings so that you could identify with them. We approached that very specifically early in the picture to tell the audience that it was OK that Stuart was talking and behaving [like a human].”

But to make that heightened reality work, the title character had to be drop-dead convincing as a mouse while demonstrating recognizably human traits--a tall order, even in today’s era of high-tech special effects. And even though digital animation seemed the obvious answer, it was not the only possibility considered, according to John Dykstra, the Oscar-winning effects artist who served as senior visual effects supervisor on “Stuart Little.”

“We explored a variety of ways to create Stuart when we began the process,” Dykstra says. “We didn’t leave any technical approach unconsidered, because we had a desire to make the character truly innovative.”

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While digital characters had been used before in other films, no one had ever attempted to create a photorealistic character whose screen time and dialogue rivaled that of the live-action stars. Compounding that challenge was the fact that Imageworks as a company had far more experience with spaceships and aliens through such films as “Contact” and “Starship Troopers” than it did with character animation.

“We didn’t know whether we could do this when we took the project on,” says visual effects supervisor Jerome Chen. “By the time we started principal photography, we did not have a final Stuart test that we could show the studio to convince them that we could do it.” (Although as Dykstra sees it, that’s half the fun. “If you know how to do the stuff that the film is asking for,” he says, “chances are the film will be obsolete by the time you’ve completed.”)

Whatever questions the team may have had about technique or chances for success, there was never any doubt about the objective. “We wanted Stuart to be the most believable character that has been done with animation yet, to the point where you can completely forget he’s animated and believe that you’re seeing a real personality,” says animation supervisor Henry Anderson.

While the live-action footage was being shot--with the actors reacting either to empty spaces or laser dots in place of Stuart--character designers and modelers set about creating an acceptably cute (but not candy-coated) look for Stuart. “We spent weeks determining how the hair lays down on his forehead or his cheek or his ears, and it’s amazing how much you can change his look by the way you twist the hair around the eyebrow,” says Jay Redd, one of four computer-generated imagery supervisors who worked on the character.

“We developed a [software] system that allowed us to sprinkle just a few hairs around on a 3-D representation of Stuart’s head, and that would give us a general direction of how we could lay the hair down on the surface,” Redd says. The reality of Stuart’s fur was of primary importance because CG figures without convincing texture tend to look like movable toys. Some 500,000 individual digital hairs were placed on Stuart’s body, and even though he is a white mouse, black and gray hairs were sprinkled throughout the fur for the sake of reality.

“It gets the organic feel of the fur,” says Thor Freudenthal, who was responsible for creative and visual development. “In previous examples, where everything looked nicely groomed and clean-cut, you see the mechanical quality of it, but here there’s a lot of imperfection that makes it very believable.”

To achieve Stuart’s facial performance, a team of 30 animators worked from 66 different “head shapes,” which provided extreme expressions for Stuart and indicated mouth movements for lip-syncing. By mixing and matching the head shapes, virtually any expression could be created. “The fact that you could blend from one shape to another really gave a palette that was huge,” says CG supervisor Bart Giovannetti. “They were essentially continuous shapes.”

Particular attention was also given to Stuart’s hands, which are his most human physical feature. “There were a lot of close-up shots where we would actually scale the thumbs specifically so it would work for that shot,” says CG supervisor Scott Stokdyk, who was responsible for Stuart’s “physiquing.”

The biggest advancement in terms of technology, however, came not in creating Stuart himself but his wardrobe. Extensive tests were done to determine the scale of the clothing and the resulting costumes themselves were mechanically correct. “What separates [the clothing simulation] from a lot of things that happened before was their intricacy,” says CG supervisor Jim Birney, who acted as digital tailor for Stuart and the film’s two other mouse characters, Mr. and Mrs. Stout. “We allowed the costume department to put together anything they wanted, and when they came to us and asked, ‘Can you do this?’ we said, ‘Yes, we’ll figure out a way.’ ”

Instead of using texture-mapping, a common digital technique in which a pattern or color is painted over a digital surface, Birney’s team used special software that allowed Stuart’s clothes to be built in panels, in the way that regular clothing is cut from patterns, and tailored to the mouse’s frame. When the camera goes in close, the weave can be seen. “We’ve had screenings where people would say they knew [Stuart] was computer-generated, but add, ‘The clothes were real, right?’ ” Chen says.

The production also pushed the envelope in the area of match-moving, in which the movement of the on-set camera is exactly duplicated inside the computer--a process that enabled Stuart to fit seamlessly into moving shots. With earlier CG technology the on-set camera had to remain fairly stationary. The ability to make match-moves with such precision, Dykstra notes, was impractical even two years ago, when development first began on “Stuart Little.” As finished shots of Stuart finally emerged (and there are more than 500 of them in the picture), early fears that he would not hold up well under close-ups disappeared, and more close-ups were ordered. “There are some shots where he’s going to be 40 feet high in the theater, and it’s absolutely perfect,” says visual effects art director Marty Kline. “You believe him, all the lights on the skin and the fur and everything works.”

Toiling for more than a year to create the most visible “invisible” special effects ever seen might seem like a thankless task, but the Imageworks team is not complaining. In fact, Chen admits that “going back to a more traditional effects film doesn’t seem that interesting. Digital character creation is where I want to be from now on.”