Cover Story: Depth Perception
Issue: Volume: 26 Issue: 5 (May 2003)

Cover Story: Depth Perception

Stanton is the latest protégé of director and creative guru John Lasseter. He not only had a hand in co-writing all four previous Pixar films but also co-directed A Bug's Life with Lasseter. With Finding Nemo, though, Stanton found a very personal project to pursue for his first solo stint behind the virtual camera: fatherhood.

The film revolves around father and son clown fish—the overly protective Marlin (voiced by Albert Brooks) and his youngster Nemo (voiced by Alexander Gould)—who become separated in the Great Barrier Reef off the coast of Australia when Nemo is abducted and thrust into a funky fish tank in a dentist's office overlooking Sydney Harbor. Buoyed by the companionship of a friendly but forgetful blue tang named Dory (voiced by Ellen DeGeneres), Marlin embarks on a dangerous trek to rescue Nemo, who hatches a few escape plans of his own to return safely home.

The inspiration for the film stems from Stanton's guilt about not spending enough time with his own son, as well as from an inspirational outing they had together at Marine World. He also drew on fond childhood memories of his dentist's fish tank. "I don't think I've watched an animated movie where the protagonist was the father," Stanton asserts. "It was funny, because every time I would pitch the story and start to talk about it, everyone assumed it was going to be from the kid's point of view. The kid was going to learn some life lesson and come back, and be a better person for it. But I became obsessed with this premise that fear can deny a good father from being one."

To convey human-like emotions through the expressions of non-human characters, Pixar enhanced its Geppetto articulation software, giving animators better control over facial features. All images © 2003 Disney/Pixar.

To prepare for animating an underwater world, the artists went straight to the source. In addition to visiting aquariums, going on dives in California and Hawaii, and studying numerous documentaries about fish and underwater life (including IMAX's Blue Planet), Stanton and company had their own well-stocked 25-gallon fish tank at Pixar. Anytime they needed inspiration, the animators could gaze at the blue tangs, royal grammas, and other assorted species. "It was the first time since A Bug's Life where we could just study [living creatures]," says Stanton. "We certainly have looked at Pinocchio and Sword in the Stone, where the characters turn into fish, just to see how people decided to caricature them. But nothing gets you more inspired than seeing the real thing."

For making the fish swim in circles, Pixar animators devised a new tool called Patht that directs the fish to follow any three-dimensional spline curves on which they are placed.

According to directing animator Mark Walsh, "The first thing that Andrew [Stanton] did on the film was to sit with us in front of the fish tank and basically pitch the story to us. The magic of the world was going down to the perspective of a clown fish and imagining him traveling through an entire ocean and encountering sharks, turtles, jellyfish, etc. You imagine moving in closer and seeing this little fish and how hard he's trying."

Stanton's choice of species for father and son was no coincidence. In addition to being cute and colorful, the clown is utterly defenseless when taken away from its coral environment. This serves Marlin's conflict well. Dory, on the other hand, is positive and optimistic, despite her short-term memory loss. "But she's a wonderful contrast to [Marlin's] character, who has all this baggage that prevents him from living life," remarks producer Graham Walters.

Perhaps the most useful resource available to the Pixar team was Adam Summers, a professor in the Ecology and Evolution Department at the University of California at Irvine, who gave a series of 12 lectures to the animators at the Emeryville campus. Among the finer points that Summers taught was the difference between "flappers" and "rowers." Clown fish, for example, use their pectoral fins to row forward. Blue tangs, like Dory in the film, propel through the water by flapping their fins.

Supervising technical director Oren Jacob led the effort to digitally re-create an organic coral reef and a vast ocean that would respond in a realistic way to the action of the colorful characters. Early on, Jacob and Pixar's technical wizards (supervised by Michael Wong) identified five key components that suggest an underwater environment: lighting (patterns of caustic 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 plant and aquatic life), murk (how the color of light filters out over distance and appears dark), and surface conditions (chops, swells, and waves that affect the lighting).

"This film is far more complicated than Monsters, Inc.," Jacob offers, "in that almost every shot involves some kind of simulation program or simulated movement. On average, there are more things going on per frame in this movie than we've done before by a pretty significant amount."

Jacob and his team first needed to create a suite of tools in the water arena. The most complex was the 3D water simulator, which allows water to interact with itself, such as when it crashes or crests, and also creates the necessary viscosity. "[For this], we expanded and modified Fizt, the fur and cloth simulator used on Monsters, Inc.," Jacob says. Martin Nugyn, John Anderson, David Baraff, Andy Witkin, and Apurva Shah were instrumental in writing the suite of tools for the 3D water simulation.

Pixar used mostly proprietary tools when creating the characters and their environments but also employed commercial software to complete the various steps of production, including (from top to bottom) modeling, animation, shading, and compositing.

In addition, a team headed by John Pottebaum and John Alex wrote a system to put surge and swell in the ocean based on speed and timing parameters that drives the entire aquatic environment. "It makes the grass move, it makes all the soft coral move, all the particulate matter move, and it even makes the fish move in place," Jacob adds. Another program, Snst—also written by Pottebaum, Alex, and their group—allowed animators to control fish in the surge and swell.

Meanwhile, John Halstead, Warren Trezevant, and others, wrote a tool called Patht to enable fish to swim in three dimensions. "This allowed us to lay out paths rather than doing it independently," Jacob comments. "We put a spline in three dimensions in and around the camera and around the scenes. We just popped the fish on and off the path." A good example of this is a shot after a submarine crashes into a wall and Marlin and Dory try to retrieve a mask that's fallen into the depths, and you see them swimming in cycles.

Animators studied the swimming techniques of a variety of aquatic creatures to re-create their movements as realistically as possible. For example, they learned that clown fish row with their fins, while blue tangs flap their fins to propel themselves for

Pixar also enhanced its Geppetto articulation software to handle the facial animation of the fish. "These were improvements in both how we connect and orchestrate different performances on the face so that when you pull the teeth back and smile, your cheek mass moves over your cheek bone and you actually get folds over your eye," Jacob explains. "We improved the articulator to give animation better control of these types of expressions. We also built some new deformers, including a special fin package that standardized how the fins work. Hands are hard to build but are a known quantity. But getting fins to look like fins and move like hands is difficult to do. The fin package had to accommodate both rowing and flapping."

Another tool, Wigglet, created under the leadership of Stefan Gronsky, analyzes how a fish moves from frame to frame and how it changes direction. "It takes that info and uses it to drive the fin deformers that animators choose to use," Jacob says. "It's their choice to use whatever fins they want."

In order to achieve the proper translucent quality of having light pass through objects under water—what Pixar calls "Transblur-rency"—animators adjusted Pixar's RenderMan to blur objects based on distance and depth. "The camera position and optical light path were calculated into the equation," Jacob explains. "With jellyfish, for instance, you blur the background a little bit on the edge of the bell; and in the middle you blur it the most; and then you have a continual gradation of blurriness based on the depth of jelly you're looking through."

A related technology called Gummy Fish was used in modeling the two clown fish. "They have a gummy quality and, as they turn to the light, you can see their skeletons and guts," Jacob says. "The program we built adds visual depth and complexity to the fish." This is in contrast to Dory, who has a more opaque, velvety texture, and other fish that are more of a metallic variety.

Since RenderMan wasn't set up to handle refraction properties quickly enough, it was also tweaked for the dentist office scenes, among others. "We built that system to work for all the shots in the tank in the dentist's office where you're looking out into the waiting room, or up through the surface at the dentist," Jacob continues.

As far as commercial tools, Pixar used Apple Computer's Shake (formerly from Nothing Real), along with its own proprietary software, for compositing. Alias|Wavefront's Maya was used to do element, set, and prop modeling. Maya was also used for some shading, and many of the effects were based on Maya particle systems. Adobe's After Effects was used for a number of shots, while most of the digital painting was done with either Interactive Effects' Amazon Paint or Adobe's Photoshop.

Ironically, the simulation efforts were so effective that the animators had to actually pull back from becoming too photoreal during the early stages of production. However, despite the breathtaking waves, coral, and jellyfish, they sufficiently caricatured the underwater world to attain the desired "hyper-reality" that has become Pixar's trademark. Thanks to production designer Ralph Eggleston (a recent Oscar winner for his direction of the animated short For the Birds), the colors were over-saturated to lend a modern Technicolor look, as if Pixar were doing a digital version of Bambi. "The entire set is like a jewel under the water," Eggleston notes.

Using a technique called Transblurrency, animators adjusted Pixar's RenderMan software to blur objects based on their distance from the viewer and their depth in the water.

As with every Pixar feature, there were significant organizational changes on Finding Nemo. Indeed, now that the studio has stepped up production with one feature every 18 months, it was imperative that the studio redouble its efforts to use crews, budgets, and file management more efficiently. Working with less than the usual 50 animators, Pixar abandoned the shots department used on Monsters, Inc. to give the crew more ownership of its work. "We consolidated departments so there is less passing of information from group to group," says co-founder and president Ed Catmull.

As a result, the studio came up with six technical teams specializing in different components and environments seen in the film. Lisa Forsell and Danielle Feinberg were the CG supervisors responsible for the Ocean Unit. David Eisenmann and his team handled the models, shading, lighting, and simulation for the Reef Unit. Steve May headed up the Sub Unit, which tackled a crucial submarine scene, shots inside a whale, and most of the above-water scenes in the harbor. Jesse Hollander oversaw the Tank Unit, which created all the elements for the kitschy fish tank that looks like an underwater Las Vegas. Michael Lorenzen was in charge of the Schooling/Flocking team, which created hundreds of thousands of fish plus key elements for a turtle drive sequence. And Brian Green led the Characters Unit, which created the look and complex controls for all of the various aquatic, bird, and human characters.

For the animators, Finding Nemo presented a whole new set of challenges, not the least of which was bringing a full range of emotions and actions to characters without limbs or traditional bodies. "In the beginning it was frustrating because we couldn't go into our old bag of tricks," explains supervising animator Dylan Brown. "We spent a lot of time studying what made fish appealing and analyzing how they move. The facial articulation became more important than ever and it had to integrate with the body movement. Unlike a human character, if a fish turns its head, the whole body might turn with it. Even our sense of timing had to change dramatically. Characters like Buzz, Woody, or Sullivan have an earth-based gravity. But fish can travel three feet in a flash. We studied their movement in slow motion to achieve that kind of action and to give it crisp timing."

"It became fun and challenging to come up with a whole new range of ways to communicate and gesture," adds supervising animator Alan Barillaro. "You don't have gravity to deal with underwater, so we discovered subtle things like when a character gestured, he would tend to drift a bit more. I found that a lot of the gestures humans make could be boiled down to eye and face movements."

Brown suggests that animating fish is like animating toilet paper underwater. "They're so loose and so fluid," he adds, "that we had to make sure we had enough resolution in the models to get the kind of finite control that we needed. We actually wrote the fin package twice because it was so hard to figure out. It's based on a whole series of rays, and you can ripple these rays down and get to super-finite controls over those."

In the end, for Stanton, who believes there is no reason why animation can't be as well crafted as live action, Finding Nemo represents another milestone for Pixar. "The drive was like, we're not telling an animated movie, we're just telling a great movie and we're letting animation be an advantage to do anything we want to tell that story," he says. "We wanted to make it feel like a filmmaker's sensibility." But it was tough trying to find that balance between the graphic and the fantastical, he adds. "So you end up feeling like you're really there, yet you kind of feel like it's a little special, a little amped-up."

Bill Desowitz is a freelance writer specializing in digital visual effects in film and animation.