At one point, one animator asked Adam Summers, the ichthyologist, where the fish's eyebrows would be. Summers responded that fish don't have eyebrows or even muscles in their face, except for jaw closers.
"We had to remind Adam that fish don't talk either," said Brown. "But they would in our film."
Flappers vs. Rowers
The animators had to learn the difference between "flappers" and "rowers." Clown fish are rowers who propel themselves by moving their pectoral fins horizontally, wiggling their entire body. Blue tangs are flappers, who flap their fins up and down to move and almost never wiggle their entire body.
"In most animated films with fish, the characters move back and forth with no visible propulsive device, and that really offends the eye," said Summers. "You don't need to be an ichthyologist to know there's something wrong with that kind of locomotion. It would be like watching a horse trot with two of its legs still. In Nemo, they're not acting in air. When they flap around, it has consequences for their whole bodies."
The filmmakers had advantages too. They didn't have to deal with the issue of gravity, what happens to a character's knees and hips when weight is put on them.
But their sense of timing had to change dramatically. The animators studied fish movements on video, slowing it down enough to see how a fish can travel three feet (90 centimeters) in a flash. "Our timing got very crisp as we learned how to get our fish characters from one place to another," said Brown.
Colors and Lighting
Getting the fish right was only half the battle. Creating an organic coral reef and a vast ocean that would respond in a realistic way to the action of the characters was equally important.
The animators needed to get five key components right: lighting (patterns of lighting that dance on the ocean floor and fog beams that shine from the surface), particulate matter (the ever-present debris that appears in water), surge and swell (the constant movement that drives aquatic life), murk (how the color of light filters out over distance), and reflections and refractions. Because fish have an almost caricatured shape to begin with, the filmmakers had to bend reality and bring the underwater world closer to the nature of the fish. Putting the caricatured fish into a quasi-real world would not work.
Colors and lighting were key. They used crystal blue lighting for the scenes on the reef, deep blue for the ocean, and murky, muddy tones for scenes involving the whale. "We had no set pieces," said Brown. "So we had to use color to let the audience know where we are."
Almost every shot involved some kind of simulation program or simulated movement. There are far more things going on per frame in Finding Nemo than in any other Pixar movie.
For one of the most challenging scenes, in which Marlin and Dory get ensnared in school of thousands of deadly pink jellyfish, techies built a schooling software based on a single jellyfish that created a simulation for the group, controlling how quickly the jellyfish swam and in what direction.
In the end, the animation has to be believable, said Brown. "You have to get into this fantasy world, forget about the technology and get sucked into the story."
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