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The Cat In The Hat: Living In A Fishbowl

Dec 1, 2003 12:00 PM, By Ellen Wolff

Living In A Fishbowl

When Universal Pictures releases The Cat In The Hat this holiday season, Mike Myers will personify Dr. Seuss' famous feline. Myers will be sharing the screen with a talking computer-animated fish, and the challenge of making that fish come alive for director Bo Welch belonged to L.A.-based Rhythm & Hues.

Of the 350 effects shots that R&H handled for The Cat In The Hat, 40 involved the animated fish. Visual effects supervisor Doug Smith characterizes this animation as relatively stylized. “The movie starts out with a real goldfish in a bowl, and then goes into the ‘Seussian’ world when the cat shows up,” Smith says.

Digital effects supervisor Chris Sjoholm describes the fish as, “a semi-cartoon character with realistic skin who lives in a real glass bowl with real water. When he's underwater he's quite glossy and iridescent, and the fishbowl reflects the whole room that he's in. We also see him hanging off the side of the bowl and he looks either wet or dry, depending upon whether he's out of the bowl long enough so that the water has seeped off of him.”

Universal's art department began the design of the fish with basic outlines that, Sjoholm says, they expanded upon and produced 20 versions. “We then built the model in the computer, and there were lots of little tweaks. We had to determine how big his eyelashes should be and how wrinkled to make his eyebrows.” Creating facial animation, notes Sjoholm, “is difficult with a character that doesn't have a bottom lip!

“Once we had an approved turntable of a gray shaded model, the road split at that point,” continues Sjoholm. “Some people went off and defined the actual look and others defined the character animation.” The latter group studied videotaped references of actor Sean Hayes reading the fish's lines. They also watched videos of Barney Fife, which director Welch had identified as an inspiration. The fish's performance subtleties would be noticeable because of his size. “He's so small that he's framed super tight to get all the emotion on his face,” Sjoholm says.

However stylized the performance, the fish's body had to seem believable. “To make his skin photorealistic, we had independent movement of the fish's scales,” says Smith. “That probably took a month of R&D. We also spent about six months developing a tornado-like vortex of water in the fishbowl. We brought in a consultant from UCLA to help us deal with the fluid dynamics.”

“A lot of research has been done in Complex Fluid Dynamics, but every CFD paper has little cheats — no one has the ultimate solution,” says Sjoholm. “For water in a fishbowl, there was no ideal theory out there.” Simulating water can produce anomalies like the appearance of cavities or a volume of water that explodes while sloshing around. “There's ‘theory’ and then there's implementation, and sometimes there are errors in both,” Sjohom concludes.

The simulation team also spent lots of time throwing spheres into the water, making sure they got good splashes. R&H's software specialists wrote plug-ins to work inside Side Effects' Houdini software for the water simulations, but most of the animation for the fish shots was handled within the studio's proprietary code.

The complex task of rendering was also done with an inhouse renderer. Because the fish often appeared out of the water — sometimes looking wet and other times dry — the lighting challenges were complex. “We had a variety of issues dealing with the reflections off the fish's scales — they had to look as if they were coated with a layer of goo,” says Smith. “There are also layers of iridescence on the fish skin that interact with the water and are reflected in it. And because the character has large eyes, we did refractions in them as well.”

Raytracing and some global illumination were necessary to achieve these effects. “We augmented our renderer to do the raytracing and sub-surface scattering and iridescence,” says Sjoholm. “We spent about four months doing R&D to tweak this. The rays bounce around far more than they would with a normal object. Every ray has to go through the front of the bowl, through some water and maybe some waves to hit the fish. Then it has to bounce back again. So there's a lot of light reflecting in all sorts of areas. We had taken photos of the environment on set and we reflected that environment on the fishbowl too.”

Motion blur was also required to accentuate the fish's movement, and the end results were huge render times. “We have a couple of frames where he's so streaked it took quite awhile!” Sjoholm admits. “But there are efficiencies that we made every step of the way. The simplest thing was to break things down into layers, or we couldn't afford to render this guy. The fish was broken down into the iridescence layer, the main skin layer, and other specular layers — there were seven layers in all. That was just for the things that made up the fish. The refraction that happens inside the eyeball is very different from the gel layers coating the skin.” To optimize rendering speeds, the majority of renders were done on Linux machines.

The final step involved compositing all of this against live-action backgrounds. R&H primarily used its inhouse compositing software Icy, as well as Apple's Shake. “To make the fish integrate properly with its surroundings introduced a whole other level of complexity,” says Smith.

“We started out doing a far simpler fish,” says Sjoholm. “But as things progressed we threw in more and more because it started looking better and better. Before we knew it, we had a pretty complex guy.”

Credit Roll

Bo Welch - Director
Doug Smith - Visual Effects Supervisor
Chris Sjoholm - Digital Effects Supervisor
David Gutman - Compositor
Mike Sandrik - Lighting Setup Supervisor
Keith Roberts - Animation Supervisor
Jonathan Cohen - Principle Software Engineer
Joe Mancewicz - Animation Setup Supervisor
Caroline Dahllof - VFX TD
Toshi Kato - Principal Graphics Scientist
Peter Huang - Principal Software Engineer
Keith Hunter - Modeling Manager

© 2008 Penton Media, Inc.