Hat Tricks
Issue: Volume: 27 Issue: 1 (Jan 2004)

Hat Tricks

Dr. Seuss created storytelling history with his magical little book, The Cat in the Hat, which, famously, uses only 220 words to tell the absurd tale of a mischievous cat that shakes up the house for two bored children on a rainy day, and then cleans up the mess before Mom comes home.

By using a combination of physical sets and visual effects, the production crew for Universal Pictures' live-action adaptation of The Cat in the Hat created a setting for an expanded story that included a Seussian neighborhood of 23 houses built on 14 acres in Simi Valley, California, a flashy car for the Cat, and a wildly transformable house. To help stretch these real-world elements further into fantasy, producer Brian Grazer and director Bo Welch assembled a visual effects crew under the direction of visual effects producer Kurt Williams. Seven studios helped create 650 visual effects shots, nearly half the running length of the film, with the majority of the work going to Rhythm & Hues (R&H), whose Doug Smith was the visual effects supervisor of record for the film.

Actor Mike Myers in cat makeup (above) and the houses (below) are real, but the sky, the curlicue clouds, and the saturated, storybook colors were created digitally by various studios. All images courtesy Rhythm & Hues/Universal Studios and Dream Works LL

"This movie has everything from the most difficult 3D work that exists to tried-and-true simple compositing," says Williams. "The most important role of the visual effects was to create a world that was based on our world as seen through a child's eyes. The houses look like houses a child would draw. The clouds are swirled, the colors are saturated, and the color palette was very specific."

In the book, the Cat and two impish Things he brings in a box turn the children's house upside down and inside out, much to the dismay of a talking goldfish. In the film, as in the book, after Mom leaves the kids home alone, the Cat appears to cause no end of trouble; the Things arrive in a box; and the fish also talks. But in the film, there's a little extra adventure as the Cat (played by actor Mike Myers) and the kids chase through the neighborhood after their dog. Inside the house, a crate releases a purple tornado. And, the house isn't simply destroyed; it's twisted into wild shapes and turned into a strange and distorted world. "It's a little like a combination of Monument Valley and Disneyland over the top of an ocean in pinks and purple," says R&H's Smith. "But even though the images were strange, they had to feel real."

In addition to creating matte paintings and 3D structures for the distorted house, R&H's 300-some shots included the talking fish and digital doubles for the child actors who played the Things. "We had a wide range of effects," says Christopher Sjoholm, digital effects supervisor, "from bluescreen out the window shots to extending the road in the neighborhood to make the environment grander, but the most difficult were the 3D effects: the fish, the water in the fish bowl, and the tornado sequence that comes out of the box toward the end."
The purple goo was formed by a crew at Rhythm & Hues with blobbies and a voxel noise field in Houdini and vMantra using the film's specific color palette.

With the exception of the lock on the box—a crab created and animated at Stan Winston Digital—the fish is the only animated character in the film, and the only one that talks. "The director wanted the fish's performance to be based on the Barney Fife character in Mayberry," says Smith, referring to the bumbling deputy played by Don Knotts on The Andy Griffith Show. "But the fish doesn't have any lips or cheeks, so all the emotion had to happen in its eyes, in the wrinkles between the eyes, and in the general body posture."

The fish was modeled and performed with keyframe animation in R&H's proprietary Voodoo software using magnets and deformations, according to Sjoholm. "We try to stay away from blend shapes except for specific poses, like when the forehead is most wrinkled," he says, "because it mooshes up the image."

Even though the fish is in only approximately 40 shots, the over-the-top, passive-aggressive character has an important role. "He fills out the ensemble for the film," says Williams. More a humanoid character than a fishy fish, he's usually partly out of the water and often standing up or slightly bent when delivering dialog, so the animators didn't have to worry much about making him swim correctly. On the other hand, having a character half in and half out of water in a glass bowl in a live-action scene meant the rendering crew needed to pull some tricks out of its hat. And the water in the bowl, which was nearly always CG, had to look and act absolutely real.

"The fish had to be lit for three different environments—above the surface, through the glass, and through the glass and the water—and it would move from one to the other or be in all three at the same time," says Sjoholm.
Refractions in his eyes and subsurface scattering on his skin helped enliven the fish and put him in the scene. With no lips or cheeks, his eyes carried all the emotion.

On the live-action set, the crew used a rig with two back-to-back cameras that had 180-degree lenses to capture 360-degree HDRI (high dynamic range image) photos for shots that would include the fish. Later, using ambient occlusion techniques, they applied colors from the images as they rendered the fish's skin, helping it fit neatly into the environment. They also used subsurface scattering for the fish to help make the character's skin look somewhat translucent. "The lenses of the fish's eyes even had refractions in them," says Smith. For rendering, the crew used Wren, R&H's proprietary renderer.

For the water, with the help of ocean-ographers from UCLA, the team created a 3D fluid dynamics engine that was built as a plug-in for Side Effects Software's Houdini. "There are lots of solutions for ocean waves," says Sjoholm, "but we were interested in sloshiness and how the water sticks to the bowl, not in cresting waves."

A raytracer in Wren rendered the water. "Usually when you see CG glass, it's easy, but our shots all had the camera smack up against the glass," Sjoholm explains. "It took a lot of bounces for the raytracers to capture everything the human eye wants to see in that environment. Sometimes we could fake it with mattes and 2D, but often we wanted caustics and pools of lights shining through the pebbles on the bottom."
To render a believable talking fish in a glass fishbowl filled nearly to the top with water (all CG), Rhythm & Hues used complex lighting techniques and many rendering layers, as these images illustrate.

The lock on the box was a mechanical crab that sprang to life, jumped off the crate, and landed on the dog, thanks to the skills of André Bustanoby and Randall Rosa in the newly formed Stan Winston Digital studio. "The crab itself was a subdivision surface created in Softimage|XSI," says Bustanoby. Rendering was accomplished with Mental Images' mental ray and XSI. "We licensed a seat of HDR Shop (High Dynamic Range image processing and manipulation software) from Paul Debevec and used that to build maps for global illumination," he says. Once the lock was off the box, the lid opened, and purple goo began pouring out and overtaking the house.

The goo that oozed out of the box and the subsequent pinkish-purple tornado it became also were created at R&H. "We used blobbies with a voxel noise field in Houdini and [Side Effects'] vMantra," says Sjoholm. "It was a big violent thing that had to be nice and gentle for the kids, so rather than picking up the actors, we had it pick up objects that became warped as they were sucked into the vortex. For every scene there were several particle simulations going on at the same time—particles screaming out of the box, twirling around the actor, and picking up objects that were distorted by the animators. One shot had 83 layers."

To composite the shots, the team primarily used Apple Computer's Shake, with some work in Discreet's inferno and R&H's own Icy compositor. "We gave the compositors so many layers to have flexibility," says Jeff McLean, sequence supervisor. "The blobby stuff had to interact with the live-action plate, so we needed to tweak the colors of shadows, highlights, mid-tones, and so forth, and blend those things in compositing to get the desired look."

In addition to these 3D effects, R&H composited live-action and CG arms and other elements to build a cleaning machine, used Alias Systems' Maya Cloth to create a car cover, and substituted digital doubles for the children playing the Things when the script called for them to walk on the ceiling or flip in the air. The team also increased the film speed so that the children wouldn't move like real kids, created 3D matte paintings as set extensions inside the house and outside in the neighborhood, and even turned clouds into 2D line drawings at the end of the film.

Typically, though, the neighborhood skies were handled by Pacific Title. "They had to take plates shot in overcast and uneven lighting, pull the gray sky out, and add saturation and color," says Williams.

"I also used a small, four-person company called Cobalt to do simple compositing and fix-its in Shake, and CG work in Maya," Williams adds. "We distributed a great deal of effects work in the last few months and needed people to turn around shots quickly. I parked the lion's share of the 3D and CG work at Rhythm & Hues because we needed the big pipeline, and then gave concentrated bits of work to smaller facilities. Three years ago, I wouldn't have given 3D bits to the small shops, but I'm finding that because of products like Maya, boutique companies can push through 30 or 40 shots on a movie sometimes quicker than the large shops with big pipelines, especially if you aren't concerned about color."

Soho Effects, for example, quickly added CG hair to shots where the Cat, stuck to the ceiling, is scratching himself and his hair drifts down. They also somehow fit a bullring into a room of the house using Shake to assemble stock footage and replicate crowds.

In addition, a small studio called Hatch, working with the studio Imaginary Forces, created the opening sequence during which the camera moves through a line drawing of clouds that segues into 3D clouds revealing the town. "It takes us from the printed page to the real world," says Williams. "And then at the end, we segue back into the book."

It's as if inside the covers of the old, beloved book, a magical world was unleashed and then neatly put away an hour and a half or so later.

Said the Cat in the Hat, "I always pick up all my playthings..."
And he put them away. Then he said, "That is that."
And then he was gone with a tip of his hat.

Quotes excerpted from The Cat in the Hat, Dr. Seuss (pseud.), © 1957, 1985 Dr. Seuss Enterprises, L.P., Random House, NY.

Barbara Robertson is a contributing editor of Computer Graphics World and a freelance journalist specializing in computer graphics, visual effects, and animation. She can be reached at BarbaraRR@comcast.net.

Alias Systems www.alias.com
Apple Computer www.apple.com
Discreet www.discreet.com
Mental Images www.mentalimages.com
Side Effects Software www.sidefx.com
Softimage www.softimage.com