Stuart Little 2: Behind the Digital Characters

  • Stuart Little 2: Behind the Digital Characters
    29 August 2002 | Leonard Teo& Ali Tezel    		 Image: Margalo (Melanie Griffith) and Stuart (Michael J. Fox) share a tender moment.

    When the original Stuart Little motion picture was released in 1999, audiences both young and old were captivated by the marvel of a photo-realistic mouse that was able to walk, talk and perform humanoid actions. At the time, it was a breakthrough not only on the grounds of digital visual effects, but that Sony Picture Imageworks animators were able to produce a character that audiences emotionally attached themselves to. Three years on, Sony Picture Imageworks took on the arduous task of producing even more compelling and challenging creature effects for the second installment to the Stuart Little pantheon.

    Concept design process and workflow
    Before the script for Stuart Little 2 had been finalized, Director Rob Minkoff approached Senior Visual Effects Supervisor Jerome Chen and Digital Effects Supervisor Jay Redd with a general sense of the digital creature effects that would be required for the film. New main characters such as Margalo and the Falcon were going to be produced digitally. On top of that, there would be more action sequences that required CGI interacting with live action. Unlike the predecessing film, Stuart Little 2 would also sport more outdoor shots filmed in Los Angeles and New York.

    Working out the logistics for the digital effects on the film found many relatively simple requirements such as a CG car, airplane and buildings, but the one area that challenged the digital effects crew technically and artistically was the creation of the birds – particularly the feather simulation.

    While the script continued to be written, the digital effects team researched almost every facet of birds possible. Jay Redd reflects, “We were out getting tons of information about birds. I was out at the zoo taking photographs while Jerome (Chen) was recording stuff from TV. We actually had a couple of falconers bring their live falcons in for research. The team digged up as much information through the Internet and books as possible and we ended up with a room full of data just on birds.”

    Falcon
    For the production of the Falcon, voiced by James Woods, Imageworks worked closely with Jim Henson’s Creature Shop -- responsible for the creation of an animatronic version of the Falcon for practical shots. Though the animatronic falcon was never used in the film, it proved extremely useful as reference for lighting on set. The team spent much time at museums and captured data on feathers from deceased falcons. They found that different areas of the falcon had distinct designs or types of feathers.

    		 

    For example, the chest area had feathers with dark teardrop-shaped designs while the abdomen area had stripes and the lower shoulder region had dots. Altogether, between fifteen to twenty distinct areas with differing patterns of feathers were identified. These patterns were digitally painted by Digital Artist, John McGee who painted variations of the twenty-five different patterns for the feather library. Shader Writer Brian Steiner developed proprietary tools and procedural shaders that allowed artists to take a set of feathers and have a texture from the recorded library applied and randomly distorted for a more imperfect, realistic effect.


    The Falcon, voiced by James Woods, required immense research into the nature of feathers.

    Altogether the Falcon had between five to six thousand feathers, many of which were placed manually. Because Imageworks based their falcon on real birds, they found that there were set numbers of feathers on wings. For example, each wing had between ten to fourteen primary feathers. “We didn’t completely invent our own bird,” says Redd, “The goal was to match a real bird first, then make it our own character.” Interestingly, even though feathers make up the bulk of a bird’s surface, many of these feathers (particularly around the face) are so fine that they appear like hair, where existing technology from the Stuart Little character could be used.

      

  • Stuart Little
    Stuart Little, the enigmatic mouse voice-performed by Michael J. Fox, also went through many technical changes for the second film. “We kept pretty calm in the first movie because we didn’t know what we were capable of,” says Jay Redd, “This second film shows a lot more of Stuart performing actions that would have been extremely difficult, if not impossible in the first film.”

    One of the challenging new shots required Stuart to pull his pyjamas over his head revealing an upper-body covered with fur. “The truth is, Stuart doesn’t look very good under his clothes,” Redd continues, “In the first movie, we use clothing to get away with the model stretching in undesirable ways on the abdomen. Suddenly, his shirt comes off and the animators led by Eric Armstrong (Animation Supervisor for Imageworks) had to re-physique/skin Stuart’s upper body so that it deformed correctly. We also had to cover the entire torso with fur, making sure that the length was right and the colors, realistic.”


    Stuart Little 2 featured more daring close-up camera work, requiring much more compelling, detailed animation and creature effects.

    		 

    Image: Note the intricate feather work on the Falcon and Margalo, in a tense dialogue between the two digital characters.

    This particular shot of Stuart removing his pyjamas was also challenging as the cloth was procedurally simulated and animators did not have realtime cloth to work with. The artists had to mime the movement of Stuart’s arms and upper body, assigning attractors to his hands such that when he grabs, the cloth will pull. This animation was then handed over to the cloth team headed by Rob House. Coincidentally, Stuart’s ears were so big that cloth was getting stuck and ripping or deforming unrealistically. The final solution was to shrink Stuart’s ears to allow space for the shirt to move over. Once the shirt was off, the ears were quickly scaled up over a few frames. This was done using "magnets" in Imageworks’ proprietary cloth simulation software to scale the ears and have the cloth deform smoothly.

    Stuart’s eyes also changed as new animation controls were added for extra refinement. One interesting challenge that faced the animators was that Stuart’s eyes do not have pupils, so audiences do not actually know what Stuart could be looking at. Although this was already an issue in the first film, it becomes more apparent in Stuart Little 2 as it required more close-up shots to better convey emotion. Rather than adding pupils, the animators noticed that when mammals move their eyes, the muscles moving the eyeball affect the surrounding skin. New controls were put in such that whenever Stuart moved his eyeballs, the skin surface would deform as if a muscle underneath was moving, giving audiences a visual clue towards what Stuart was looking at.

    Margalo
    Stuart’s new friend Margalo, voiced by Melanie Griffith required a different angle to production. Unlike the Falcon, that had a gruff, aggressive look, Margalo required a more feminine outlook to portray her tenderness and make her relationship with Stuart believable. Various cinematography techniques were applied digitally such as soft lighting, soft shadows and blooms to achieve an almost ‘glamorous’ appearance for Margalo. Rather than doing more research on how to produce soft-looking feathers and fur, the digital artists found that it was easier to simply pull a matte around Margalo’s head and apply a soften/diffuse filter to the masked region in post.

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  • An impressive aspect of the movie is the interaction between characters – notably between Stuart and Margalo. One of these shots has Stuart taking a scarf and placing it on Margalo. In this case, rather than using a completely cloth-simulated scarf, the animators required control and thus rigged the scarf with a skeleton to achieve this. It took many iterations for the animators and cloth team have the scarf settle and drape a certain way on Margalo. Sometimes, they would stretch one bone more than another, causing the texture to distort on the scarf unpleasantly. Although the shot looked simple enough on screen, the amount of manual and technical work required was substantial.


    Jay Redd, Digital Effects Supervisor for Stuart Little 2, will be speaking at 3D Festival/LEAF, London 2002..

    Snowbell
    Snowbell, the clever and manipulative white feline from the first film returns and assists in the rescue mission with Stuart. The only shot in the entire film that required a fully articulated 3D Snowbell was where he was in a bucket hanging from a building. Other than that, all the cats were live animals that were digitally altered or had 3D elements composited in post. Jay Redd reflects on the difficulties faced when working with domestic cats, “The problem with cats is that they have a reputation of not willing to do anything that they don’t want to. Animal stunt coordinator Boone Narr trained the cats for nine months prior to shooting.”

    		 

    Image: Hero shot of Stuart and Margalo. Note the layered feathers on Margalo and the fine fur on Stuart.

    In reality, there were four identical cats playing Snowbell. This was required as each cat could perform specific actions better than others. For example, one cat named “Prince” was able to sit still for long periods of time without getting agitated and running off. “Rocky” was able to run from point to point for any action sequences requiring Snowbell to travel, while ‘Tuffy’ was extremely good at being hyperactive and fighting. Despite the well-trained cats, the filmmakers still needed to do much experimentation and in some cases had as many as twenty takes per shot just to get it right or to use the various performances to create new ones in post.

    For cases where Snowbell talks, animators would digitally create a talking cat’s face and composite this with the live plate. This was Imageworks’ first movie that required face-replacement and due to production deadlines, half the shots were shared with Rhythm & Hues.

    The process of face-replacement is very lengthy and according to Jay Redd, “hasn’t gotten much easier in six years”. The three points on a cat’s face that do not move are the two tear ducts and the nose. Once this triangle is found, the cat’s head can be matchmoved. Oft times, the cat had its tongue out or was meowing, and these had to be painstakingly painted out. Whiskers also had to be removed as the talking motions would create new movement. An entire muscle animation system for the face was created for animating Snowbell realistically, and all the elements such as blinking, eyes, whiskers, fur, jaw, tongue and teeth were digitally created. Not much of the process was automatic, making the face-replacement shots rather time-consuming.

    Overall, the biggest challenge for the digital character effects crew was that the animals are based on real-life counterparts. Audiences are already accustomed to seeing birds, mice and cats, requiring a realistic appearance for these characters. On the other hand, these characters played major roles and needed to perform humanoid actions such as talking, or hand movements and facial expressions, not to mention complete interaction with live action environments. There was a fine line between recreating reality and producing characterized , but captivating performances. Sony Picture Imageworks was able to conquer both feats as crowds of children and adults are simply engrossed in Stuart Little’s adventures rather than screens full of digital effects. [3DF|CGN]

    Credits
    Words: Leonard Teo
    Interview: Ali Tezel
    Images: Sony Picture Imageworks
    Special thanks to: Jay Redd, Mary Reardon, Amy Tesser & Mara Levin

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