Stretching into a New World
Issue: Volume: 32 Issue: 7 (July 2009)

Stretching into a New World

Read in-depth features about how cutting-edge CG was created for various movies making Oscar buzz.

Blue Sky Studios re-creates its popular multi-species ice Age Family for the third time. With the help of flexible rigging and new effects tools.

The unlikely group of animals in the Ice Age pack is back, and this time they’re in a family way, even more so than before, in Twentieth Century Fox’s third film in the franchise: Ice Age: Dawn of the Dinosaurs, created, as always, by Fox’s Blue Sky Studios.

“Ellie is pregnant,” says director Carlos Saldanha, referring to one of the two mammoths in the group. The other mammoth is pack leader Manny. “Manny is feeling crazed about the arrival of the baby, and his friends feel left out of the family unit, so there’s a chance the herd might be split up.” So, Sid, the loveable goofball sloth, decides to take family matters into his own hands.

“Sid falls into a mysterious ice cave, where he encounters three ginormous eggs,” Saldanha continues. “He treats them as his own, and when three adorable dinosaurs hatch, they call him ‘mommy.’” The real mommy, however, is not amused.

An unlikely custody battle for three baby dinosaurs hatches the plot in Ice Age: Dawn of the Dinosaurs, which will be shown in stereo 3D

“She takes the babies and Sid with her, so now our friends have to go forth to this unknown place to rescue Sid,” Saldanha explains. “But Sid fights to keep the babies all the way through. So, we have a lot of comedy and fun action, and we go to a new, tropical world forgotten by time. We also meet new characters. Buck is a weasel trapped in the lost world. And, Scrat meets a girl, Scratte.” Scrat is the saber-toothed squirrel that has starred in his own short films without ever saying a word.

Sexy Squirrel

Animators needed to respect the personalities and performances already established for the returning characters, but the new characters opened new animation opportunities—especially Buck and Scratte.

Lead animator Hans Dastrup was character lead for Buck, and senior animator Jeff Gabor was lead animator for Scratte. Dastrup explains the organization: “We had two animation senior supervisors on the film who work closely with the directors and look at everyone’s shots each morning. Under those supervisors are the lead animators. For this film, it was me and Juan Carlos Navarro. And then we had three senior animators. Those are our official titles. But, every character in the film has an animator assigned to it, so half the permanent staff also had a second title as character lead.”

Animators took advantage Blue Sky Studios' flexible rig to twist the one-eyed Buck's CG body into shapes rivaling those of hand-drawn animated characters.

Both characters benefited from advances in rigging developed for Horton Hears a Who (see “Poetic Justice,” March 2008). “The rig is extremely flexible,” Dastrup says. “We can shape, sculpt, stretch, squash a character almost any way we want, which allows us to get close to what 2D animators have been doing for decades.” The rigs have blendshapes built in, but much of the shaping happens through the joint systems, which allow the animators to freely push and pull parts of the geometry.

For example, although Scratte shares some of the characteristics of the irrepressible, acorn-obsessed Scrat, she has a distinct personality—actually, personalities, plural—and the rig helped animators accent those personalities. We don’t know whether her goal is to have Scrat fall in love with her or to steal the acorn. “Scrat’s instinctual,” says Gabor. “She’s a slicker, sexier, smarter version of him, and she uses intelligence and sweetness to get the acorn. So it becomes a love triangle: Scratte, Scrat, and the acorn.” When Scratte is acting sexy, the animators used the flexible rig to sculpt her body with a small waist and a big chest and butt. When she’s acting cute and innocent, they give her more of a potato shape, like Scrat.

Scratte’s dual personalities and Blue Sky’s flexible rigging meant that it was particularly easy for the animators to slip off model. “That’s the downfall of having so much control,” Gabor says. “She was especially difficult to keep on model. We needed to keep her looking seductive, and a lot of minute details affected her appeal. It was easy to make her look ugly if we weren’t careful.” One trick was to keep her mouth closed.

“When she opens her mouth, she looks like a coyote, so almost 90 percent of the time she doesn’t open her mouth,” Gabor says. “Scrat, on the other hand, the uglier he is, the more pathetic he is.”

Twisted Fate

Animators working with Buck also needed to be careful to keep the weasel appealing. To make Buck look like an untamed animal, the character designers gave him long, sharp teeth and a patch over one eye. “We’d pose his mouth and teeth to give him a wilder look,” Dastrup says. “Buck is trapped in a lost world filled with dinosaurs, and the isolation has driven him a bit crazy. He’s a survivor, but he’s a bit delusional. He might hear a rock calling him, or a bush. But, he’s a lot of fun, and he risks his life to save Sid.”

Buck has a long, weasely spine, so Dastrup and the 10 animators working with him benefited from the rig’s agility, per­forming some extreme animation. “Buck used his spine to his advantage, to move around in a dangerous world,” Dastrup points out. “The animators would twist him, tie him up, wrap him around things, and use the rig in a way that was a lot of fun.”

Gabor points to a particularly awesome shot: “They twisted him 360 degrees, like a towel squeezing out water.”

Dastrup elaborates. “Buck is coming out of the water when we first see him,” he says. “To wring himself out, we twist his body 720 degrees, as if we were wringing a towel, and then he jumps in the air and dives down, like a missile in a corkscrew spiral, to get inside a flower. Three hundred and sixty degrees wasn’t fun enough.”

Although the animators had controls and ways to clean up any crashing geometry resulting from all that twisting and wrapping, it wasn’t often necessary. “The spine rig handled a lot,” Gabor says. “We could stretch him, create a C shape, and even create an E shape. We’re pushing the CG art form and trying to go as far as traditional animation has gone. I think everyone was pleased with how well it worked.”

At the peak of production, nearly 70 animators worked on the film, with about half hired temporarily. “We have a lot of teachers at Animation Mentor,” says Gabor, “so we draw from the students there. For the most part, the people we hire are pretty close to just out of school—on their first or second job. Or, they are going through a career change and trying to get into the animation industry. We train them for two weeks, and they’re on their way.”

To help the animators, character leads create pages with dos and don’ts for each character. And, animators often sketch out poses using a 2D program developed in-house. “Animators use it to pitch ideas, plan shots, and brainstorm,” Gabor says. “It’s like a light box—you can see the drawings underneath and flip through them to see them in the context of shots around them. You can also take them into [Autodesk’s] Maya and use them as an underlying structure for animation.” Animators also videotaped themselves for acting reference and sometimes even showed directors that footage to get an OK for a performance idea.

Steamy, Snowy Atmosphere

Although proud of the performances that the animators created for the film, Dastrup and Gabor are quick to praise the rest of the crew. “The other departments did such an amazing job with the look of the film,” Dastrup says. “We so often have sequences with a stylized look that’s better than real life. It really draws you into the environment.”

Helping to create that environment was an effects crew comprising 12 TDs and two effects animators. “We were used to creating effects for the ice world,” says Kirk Garfield, visual effects supervisor, “but the lost world contained effects we hadn’t done before. In a nutshell, the biggest hurdle was the sheer volume of effects.”

Garfield e-mailed a list of 64 effects that the crew created—from bubbles to various types of water, with snow, stink bombs, steam, dust, mist, lava rivers, lava falls, lava pools, and many other effects in between.

For the volumetrics, which include steam, smoke, and clouds, the studio had used an in-house technique called “smaug” in the past, in which they’d texture intersecting spheres in 3D—in other words, attach attributes such as density and color to geometric primitives. “That limited the motion and look we could create,” Garfield says, “so for this film, we evolved Smaug into SmaugVox. That allowed us to generate voxel data with Maya fluids that we exported to our [proprietary] Studio format, and render in voxel space within our renderer.

New technology allowing more detailed control and interactivity than before helped technical directors at Blue Sky Studios put footprints in the snow for Manny and Ellie (above left) and Sid's new family (above, right).

In terms of motion, Smaug rendered Maya particles as foggy blobs that moved in whatever way a technical director might move the particles, which worked well for small effects. However, for larger areas and for interaction with characters, it was limited. “The sheer number of foggy Smaug blobs you would need would cause render times to spike,” says Andrew Schneider, effects TD. On the other hand, “SmaugVox takes a Maya fluid volume and renders it as fog,” he says. Because it is one volume, it renders faster without gaps. “In addition, you get a lot of cool billowing fluid motion for free, and the effects TDs don’t have to force Maya particles to move naturally.”  

As for the look, Hugo Ayala in the R&D department states that previously, when the objects described were semi-transparent, the raytracker had to push through the geometry and compute the contribution of all the elements inside in little increments as they moved through the volume. In SmaugVox, the process is simpler: Each time the tracker needs to compute a value, it interpolates it from the grid, the volume, rather than loop through all the Smaug geometry.

This was especially important for a “Mist Monster” sequence during one of Buck’s flashbacks, but the crew also used it for snow, dust, and other effects when it needed interaction between characters and these effects.

Footprints in the Snow

In the ice-age world, one interaction between the characters and the frozen world happened constantly: footprints in the snow. In the past, some were texture-based, and some were 2D fluid simulations. None were interactive. “We needed something more robust for this picture because we had 100 shots to do,” Garfield says. “We worked with R&D to come up with a tool that allowed more detailed control and interactivity.”

The tool, a plug-in for Maya, looks at the intersection of the geometry and the ground plane, and creates a displacement on the fly that a user could see within a couple of hours in Maya before rendering.

Attaching snow to fur was another problem solved in an efficient way for this film. Working with the R&D department, the team created a method, using Blue Sky’s fur-generator technology, for retrieving the position of every hair on an animated character. With that information in hand, they could add or remove snow from the characters as they walked or fell through the snow, based on animated signals in Maya or at render time; or, they could accumulate it on the fur during a snowstorm and remove it when the characters brushed themselves off.

According to Sean Palmer in the R&D department, they fed the point data into the studio’s voxel-based particle renderer. “Rendering fur and particles in voxel space allows us to have millions or even billions of source points or curves that can be averaged into and rendered as a single grid,” he says. “This saves render time and reduces chattering because no particle or hair is ever smaller than a single pixel.”

The other technical advance for this show centered on lava, which flows in the new, lost world. “We collaborated with the materials and R&D departments to come up with an efficient way to visualize the flow of lava and add displacements,” says Garfield. “The lava is a thin layer of particles that ride along a surface.”

Ayala explains: “The particle-simulation engine is exactly like other particle-based simulation engines; however, this solver is designed to work primarily along surfaces and requires no settling period. It takes in a description of the lava surface and computes a plausible configuration for an already settled flow in a few seconds.” This means the TDs have more time to experiment.

The R&D department also helped the modelers create the lost world. “We built plant geometry using the fur-grooming system,” says Maurice van Swaaij, R&D manager. “Instead of having modelers build plants, we generated them procedurally. It was as if you were to take a big field and put hair on it, and then deform the hairs.”

Double the Fun

Although this is the first stereo 3D film for Blue Sky, the challenges were more creative and workflow-related than technical. “We couldn’t cheat the effects in space like we have done in mono films,” Garfield says. “It was also important to allow extra screen space for the second eye, to make sure the effects have coverage.”

Similarly, the animators had to be mindful of cheats that they used to do. “If we have one character far in the distance and another close, when they tilt their head in 2D, they’d be looking at each other,” Gabor says. “That wouldn’t fly in 3D.”

The animators didn’t work in 3D but could quality-check their shots to determine if they were accurate or not. “It took a little getting used to at the beginning, but it wasn’t a big leap,” Dastrup says. “We got a feel for it after the first couple of sequences went through the pipe. It’s a popcorn movie, so lots of sequences have a roller-coaster type of experience. We stayed away from the gags, but we took advantage of stereo to amp up the fun and energy.”

Because stereo was new to the studio, the crew spent time assessing workflow issues, deciding whether to render one frame at a time or two frames at once, and considering the ideal distances for the cameras. “We considered how young of a person we wanted to go to the movie and not get nauseous,” van Swaaij says, “and decided to use the smallest distance for the smallest viewer. Then, we needed to decide how big the theaters were. We could make a stereo set that looked great on a small screen but would cause trouble on a big screen. The worst case is a very young kid in a gigantic theater, so that’s what we had to deal with. I pooh-poohed all this stuff in the first place, thinking, ‘Do I really care?’ Stereo never worked for me. But we found a method that worked, and I see stereo pretty well. And, yes, I do care.”

To create the stereo version, Blue Sky had a special stereo team with both artists and technicians who started with a rendered right eye and created the depth effect by moving the camera for the left eye. “Deciding how much depth on a per-shot basis was an extra step,” van Swaaij says. “But the stereo works great.”

Blue Sky's flexible rigging system helped animators accent Scratte's dual personality with body shapes that ranged from seductive to innocent.

For Saldanha, the goal was to have the stereo bring the audience closer to the characters and to the world. “We avoided poking the audience in the eye,” he says. “We paid a lot of attention to character placement. We didn’t want the movie to feel gimmicky. But, we have some amazing stereoscopic action sequences that feel three-dimensional and fun.”

Saldanha has been at Blue Sky for 15 years now, and directed or co-directed all three Ice Age films, so for him, the experience is as much a family affair as the story. “I knew pretty much everyone on the team,” he says. “And the characters are my children. I love them all. So it was a feeling like meeting my family again. We have evolved so much, we keep finding ways to enrich the experience yet keep the essence of the characters and still satisfy the audience with something new, not just a sequel. It’s a brand-new movie with characters you love.”

Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at