Acorns and Aliens

This year, once again, films produced at Pixar and Blue Sky are among the five short animations receiving Oscar nominations: Gary Rydstrom for "Lifted," his directorial debut at Pixar, and Blue Sky’s Chris Renaud and Michael Thurmeier, also making their directorial debuts, for "No Time for Nuts." (The other three nominees are "The Danish Poet" directed by Torill Kove, a Mikrofilm and National Film Board of Canada Production; "The Little Matchgirl" by Roger Allers and Don Hahn, a Walt Disney Pictures Production; and Szimplafilm’s "Maestro" by Geza M. Toth, a Kedd Production.)

Although Rydstrom hadn’t directed an animated film since his student days at USC’s film school, he was sound designer for Pixar’s first shorts, "Luxo Jr." and "Tin Toy," as well as most of the studio’s feature films. "I loved the shorts," he says. "So, the first thing I wanted to do was a short. I knew that would help me get my feet wet. There was a lot about computer animation that I needed to learn."

At Pixar, Rydstrom pitched three ideas to John Lasseter, who picked "Lifted," a story about an alien trainee trying to abduct a farmer. "I was sitting in bed before coming to Pixar, wondering what short I could make," Rydstrom says, "and I imagined an alien light beam trying to pull me out the window but missing. That’s how it started. Then, I put alien abduction and driver’s ed together."

The film opens with a light beam shining through the upstairs window of a farmhouse. The beam surrounds a sleeping man, lifts him off his bed as if he were levitating, and pulls him headfirst toward the open window. But the beam misses the window and bonks the man’s head on the wall. Inside a nearby hovering spaceship, a gangly green alien behind a console filled with toggle switches moves the beam and the man inside, and aims for the window again. A rotund supervisor watches.

Remembering what it was like to be a 16-year-old taking a driver’s test helped Rydstrom hone the humor and emotions for the film. "Your body is not normal yet, and your emotions are out of whack," he says. "I thought it would be fun to put that triumph, joy, panic, and shock into an alien character."

Katherine Sarafian, who had been production manager for The Incredibles, came on board as producer in October 2004 and began organizing a crew, many of whom, like Sarafian and Rydstrom, moved into new roles on the film. She cites, for example, animator Gini Santos, who was the "Lifted" supervising animator, production artist Mark Cordell Holmes, who became production designer, and Tim Best, a senior lighting artist on Cars, who took on the role of lighting supervisor.

The first person Rydstrom worked with, however, was story artist Jeff Pidgeon, who helped turn Rydstrom’s memory of his driver’s ed instructor into "Mr. B," the teacher/supervisor in the film (so named because he never gives a grade above a B). "My instructor weighed about 300 pounds," Rydstrom laughs, "and he was green, I think."

Bud Luckey, Jason Deamer, and others at Pixar developed "Stu," the student with the inverted lightbulb shape and a helmet that’s too big for his skinny head. Both characters are made of green, gelatinous, translucent material that looks a bit like aloe vera gel, complete with bubbles inside.

Tiny Bubbles

The bubbles played more than a fanciful role. "At Pixar, we want to have believable materials, yet still do wild animation," says Rydstrom. "The aliens’ elastic material let us get away with a Tex Avery and Chuck Jones style of animation—the top of their heads can twist independently from the bottom. And, the bubbles were part of making you believe the material could stretch."

Character supervisor Bill Sheffler hand-sculpted the bubbles by starting with spheres, making them non-uniform, and then manipulating them into a few dozen likeable shapes. Overall controls made it possible to scale the bubbles around their centers if they seemed too big from particular camera angles.

To rig the bubbles, the crew worked with tools under development in Pixar’s R&D lab. "We have some exotic new rigging tools that can move things inside a character and drag the surface around," says Polson. But, the "Lifted" team wanted the opposite: They wanted the skin to move the internal bubbles. That way, if an animator moved a character’s arm, the bubbles inside would automatically drag along with it.

"We went to R&D and asked John Anderson if he could rig the characters in reverse," says Polson. "He said, ‘That’s hard,’ then he thought about it and said, ‘Oh. That’s easy,’ and then later in the day, ‘It’s done.’ It’s very cool. It’s like the skin is a huge lattice deformer for the bubbles."

Final Mr. B is made withbase shading withsubsurface scattering, deep scatterillumination, occlusion, raytracedbubbles, arm and head ramps tocontrol bubble density in compositing,and an exterior silhouette fortransparency and refraction.

Although the team ran tests in which Mr. B jiggled enormously, Rydstrom felt they were losing the acting performance. So the technical directors dialed it back. "The animation on the characters is very precise," says Polson. "Mr. B conveys a tremendous amount of emotion with a deadpan face." So, when he clicks a pen, he jiggles a little, but it’s subtle.

Bouncing Light

Also subtle is the sophisticated version of subsurface scattering that bounces light inside the characters, especially within big Mr. B. Typically, subsurface scattering rays stay close to their entry point on the surface. "We usually take the illumination at a given spot on a character’s skin and allow it to blur itself inside the geometry," explains Polson. "The light hits the nose, bounces around inside, and heads back for the camera a few millimeters away from where it went in."

The foggy light beam, the black, nighttime pixels, and the directionallighting created interesting challenges for Pixar’s lighting team.

In other words, the light that you see on Mr. B’s front contains a component of the color from his back after being filtered through his body. "Some people might do that with raytracing by firing lights from the front," says Polson. "And, there’s a bit of that going on. But our shader is calculating the light hitting him, letting that blur through the body, and kind of tracking the progress of the light energy through his body."

Polson believes that eventually people will create better tools for writing shaders that consider light at a point as a function of all the other points on the model and all the other lights in the scene. For now, though, the process requires handcrafting.

"Writing these shaders takes a completely different mind-set," he says. "Rather than knowing only that I’m at a point and which direction I’m facing and the local color, now I have other points around me and a model behind me, and it’s this deep, and light is coming through it, and the colors are shifting, and there are all these other things I’m tracking, too. The TDs at Pixar and in the industry are still figuring this out; we’re developing the craft of writing these things by fits and starts. Over time, though, a natural way of doing this will emerge."

As for more typical effects, Michael Lorenzen drove the spaceship and handled the particle effects, while Polson organized the enormous control board filled with toggle switches. "I made the console the world’s worst interface," Rydstrom says. "Stu has a manual, but every page has the same array of black dots, so there’s no way for him to ever learn how to use this equipment."

Polson programmed the switchboard, creating toggles from RenderMan curve primitives, like little spikes of hair, which became geometry during rendering. Because the program generated the toggles procedurally, he could easily change the number of rows and columns and the spacing between them. "We adjusted the toggles for almost every shot to make sure there were no moiré patterns or lines that led the eye where we didn’t want it to go," says Polson. Edwin Chang added code in Pixar’s proprietary rigging system to the procedural toggles that detected when Stu’s arms moved over the toggles, and depressed each switch appropriately.

When Stu’s hand moves over a toggle, you can see through the edge of his finger to the toggle or console beneath. "It’s as though he’s substantial on the inside and encased in something clear on the outside," says Polson. He and Mr. B are both translucent on the inside but with a transparent rim. "But Stu is so thin his transparent region is just one or two pixels. It made him hard to light."

Lighting, in fact, was particularly difficult for "Lifted." "There are probably more black pixels and near-black pixels than in anything we’ve done before," says Polson. "We had foggy beams of light with particulate, and we had to be very careful about how each piece of geometry shadowed the fog and how it propagated through."

Got Rhythm?

Stu scans the instruction manual as Mr. B watches, but he needn’thave worried: Pixar’s code moved the switches automatically.

"He pursues his nut through time, through a series of mishaps," says writer and co-director Chris Renaud. "And that’s the story in a nutshell."

"No Time for Nuts" is the result of an internal contest. The studio had created "Gone Nutty" for the Ice Age DVD. Similarly, they wanted another short film for Ice Age: The Meltdown. After reviewing several ideas for the new short, Meltdown director Carlos Saldanha and producer Lori Forte chose storyboard artist Renaud’s time-travel idea. Supervising animator Michael Thurmeier joined the project as co-director, and Kirk Garfield, a visual effects lead, stepped up into the role of visual effects supervisor.

"The film gave many of us the opportunity to elevate our positions," says Thurmeier. In addition to Renaud, Thurmeier, and Garfield, James Palumbo became the editor, visual development artist Michael Knapp became the art director, and Haji Uesato, a sequence lighting lead, supervised the "Nuts" lighting.

"No Time for Nuts" tells a loony, fast-paced story that has Scrat moving quickly from one iconic bit of history to another. "He begins in the ice, where he accidentally starts the time machine," says Renaud. "It zaps his nut. He shakes the machine, and it zaps him, as well. We cut to a beautiful green forest, where the acorn is wedged under a rock. Scrat looks around and sees a sword in a stone. He grabs the sword and pulls it out. Music swells; his hair blows in the wind."

A flurry of arrows aimed at the squirrel shatter the mood. Scrat runs back to his nut, frees it, narrowly escapes another barrage of arrows, and somehow frantically hits the buttons on the time machine, which zaps him into a Roman coliseum. And so it goes. "The scenarios get shorter and shorter as we pace through the film," Renaud says.

The “Nuts” team created the timemachine’s zap effect through a productionefficient collaboration among the lighting,compositing, painting, and effects teamsand the art director.

"We had shots that were literally only 12 frames long," says Thurmeier. "We’ve done matte paintings before, but not to this extent. We had so many locations and so many sets."

A team of effects artists coped with the film’s complexity. Blue Sky Studios’ tool set includes Autodesk’s Maya and Inferno, Apple’s Shake, Next Limit Technologies’ RealFlow, and the studio’s own CGIStudio programming language and raytracing-based rendering software. The "Nuts" crew used most of these tools—even RealFlow, which they used to pour tiny acorns through an hourglass.

"We were coming off Ice Age: The Meltdown, which had as many as 26 effects artists, so we had a lot of people ready to take on the effects for this project," says Garfield. "It was a dream project for effects. There were so many sets and so many types of effects—and none of the effects were water effects. We were all eager to do everything we could."

So eager, in fact, that the effects team often did more than the directors requested. "Their enthusiasm was incredible," says Renaud. For example: "In one scene, Scrat has a nuclear blast behind him. It’s a 10-second shot, and we thought they’d do it by manipulating a matte painting. But, the effects guys created a 3D mushroom cloud, and augmented it with lighting, paint, and roiling clouds. They took it to the next level even though it was on-screen for seconds."

Time for a Change

Although many of the sets and effects, like the nuclear blast, last for only seconds during the film, because the time machine’s zap effect would appear throughout, the team focused their attention on that effect early in the project. "We needed to come up with an efficient method for doing it, because the effect involved the lighting, compositing, painting, and effects teams," says Garfield.

The time machine Scrat is holding has zapped him into the role of afi g leaf for Michelangelo’s “David.”  

To create a plasma wave generated by the time machine, the effects artists rendered curves with Hermite expressions. Garfield explains: "We use sine and cosine to make wavy curves, but instead of the sine waves, we used expressions with these more complicated equations to make the lines look like plasma."

Scrat’s quick zaps through iconic moments in time caused the Blue Sky crew to create dozens of setsand effects. Here, Scrat pauses for a moment of glory before the arrows start to fly.

By working with Knapp, the team developed a way to generate effects elements that they enhanced in lighting and compositing to create the tunnel. "The collaboration was similar to what we did with the time-machine effects," says Garfield. "And we used our plasma tool to define the tunnel. It’s like an energy hole that fills up with power."

To fill the tunnel with energy in the spirit of what Garfield describes as cheesy time tunnels in old movies, the team used Maya particles. "We exported the particles to our proprietary renderer and added lights and glow effects," Garfield says. "Then, we gave those elements to our compositing team."

Shake master and lead lighting technical director Dan Cayer then combined those elements with other effects, artwork from Knapp, and animation from the layout and animation departments. "He probably had 100 or so layers," says Garfield.

Cayer was also instrumental in creating the nuclear blast effect. "Our effects CFD (computational fluid dynamics) lead came up with an element rendered right out of Maya," says Garfield. "Dan Cayer took that element, which was 60 percent there, and combined it with a method we employed during a geyser sequence in Ice Age: The Meltdown." That method involves mixing particles with matte paintings in Shake.

All told, the project took about a year from the initial pitch to the final scoring and sound, but most of the work happened between October and June, with a month off in April following Ice Age: The Meltdown’s release.

"The shorts are a great way to keep everyone active and enthusiastic between pictures," says Renaud. They also spur the studio to try new techniques for the next picture—in this case, the animated feature Horton Hears a Who, scheduled for release in March 2008.

"I don’t think we developed any new tools," Garfield says. "But we worked in new ways that’s actually helping the Horton Hears a Who production. Because we’re trying to stay true to Dr. Seuss’s style, Horton is heavily stylized from an effects standpoint. So, we’re working to come up with ways to share effects, rendering, and animation with design early on, so there won’t be any surprises at the end. And, we’re working closer with compositing—not necessarily rendering effects in-camera, but giving compositing more of a chance to plus our effects."

For Renaud, Thurmeier, Garfield, and the rest of the "No Time for Nuts" crew, the short film also gave them a chance to harness their talent to the "great Blue Sky engine that produces phenomenal stuff," as Renaud puts it.