One Step at a Time
Issue: Volume: 33 Issue: 1 (Jan. 2010)

One Step at a Time

Of the five animated features nominated for Golden Globe awards this season, two—Coraline and The Fantastic Mr. Fox—used stop motion, one of the oldest animation techniques. Even so, for Mr. Fox, as with most animated films these days, computer graphics played a role. CG artists working on the film, though, found few similarities to hand-drawn or CG films.

“Stop motion is quite strange,” says Tim Ledbury, visual effects supervisor for Twentieth Century Fox’s The Fantastic Mr. Fox. “It’s more like making a live-action film than a CG film. As far as I was concerned, the foxes could have been actors. But, it was like live action in slow motion.” Animators creating a stop-motion film work one or two frames at a time, moving tiny models into various positions and then filming them.

“Rather than waiting for a plate, I could sit at my desk, watch a shot, grab a frame, and do a quick TIFF composite to check it,” Ledbury says. “If, say, a character’s head was getting too close to a problematic area, I could run down and stop the animators, and they might move the head. It was quite nice to have that control.”

Although the animators worked two frames at a time, the overall production happened at a faster pace. “On a live-action film, we might have three units shooting at one time,” Ledbury says. “On this film, they had 30 units running on different stages at the same time. It was much busier than I envisioned. I thought it would be leisurely, but it was quite intense all the time—sets going up, sets going down, shots coming in at different times, meetings about sets coming up next.”

Because Ledbury came onto the film early as a concept designer, he continued working on designs all through the project, in addition to supervising the visual effects work. “Stylistically, Wes [Anderson, the director] wanted as much as possible in camera,” Ledbury says. “Our shot count was high. We touched 75 percent of the film. But of the 617 VFX shots, only 400 have typical visual effects work. The others are fairly simple rig removals.”

A Sense of Scale
An in-house crew of 28 worked on 500 shots. Stranger, now NVizible, did 30, and Lip Sync Post handled 80. In addition to removing animation rigs, the visual effects crews extended sets, duplicated sets, lit and rendered scenes, painted skies, and composited characters filmed against greenscreen into CG and miniature backgrounds built in various scales.

“We had normal scale, animal scale, and human scale,” Ledbury says, ticking off the various-sized characters the compositors needed to deal with. “For the animals, we had full size, half size, micro and mini-micro. For the humans, we had full size and half size. The full-size human and half-size animals worked together, and the half-size humans and micro animals worked together. And then we had a full-scale animal set, a micro animal set, and a full-scale human set. All those mixtures created issues.”

Animators working on 30 stop-motion stages kept VFX supervisor Tim Ledbury hopping, to be certain his crew who would touch 75 percent of the film extending sets, adding skies, removing rigs, compositing characters into backgrounds, and so forth wouldn’t run into problems.

Ledbury takes a breath and continues: “Plus, although every shot is a main pass, we did multiple passes for safety—different lighting stages, sets with puppets and without puppets. The amount of shots and the volume of data coming at us all the time was the hardest thing about the film. Working with the CG stuff, doing the set extensions, was the haven. That was the fun.”

Before production began, Ledbury had previs’d about 100 of the prickliest shots working in Autodesk’s Maya and Apple’s Shake, which were the main production tools along with Mental Images’ Mental Ray for rendering and Andersson Technologies’ SynthEyes for matchmoving. “We did previs for technical reasons, not for story points,” he says. For example, they used previs to determine how many sets of what size they needed to build.

Perhaps the most expensive and complex set—and shot—the team worked on was one in which Mr. Fox comes up through the floor of a giant chicken shed.

The shed was a miniature, so they could photograph it and use the photos as textures for set extensions. “But, we didn’t have the full shed,” Ledbury says. “We had to duplicate it and make it four times longer, add in CG pipes and feeders, and build the roof.”

The animators worked with Mr. Fox and a group of about 60 chicken puppets in front of a greenscreen, but the director wanted more, so the visual effects crew added another 300 or so CG chickens to match the stop-motion puppets. “It took everyone in the CG department because we had to turn the shot around in a week and a half,” Ledbury says. “But we enjoyed the challenge. This, the attic, and the supermarket were the biggest shots.”

For the supermarket shot, the production team had filmed characters dancing on four shelves. The VFX crew built CG versions of those shelves to extend the set and mapped photographs of the miniature shelves onto the digital shelves. “The model-making department made such highly detailed sets that we could use photos of the models for textures,” Ledbury says.

Because the models are so tiny, though—the supermarket set was six inches tall, the attic was 10 inches by 12 inches wide—they had depth-of-field issues. “We photographed multiple angles, and photographed the models in stages, starting with the foreground,” Ledbury says.

To complete the supermarket, they also extended the floor, built a ceiling, and added CG lights that the camera would have passed through on a real set. “The CG lights came from a photo of a full-size set that we mapped onto geometry,” Ledbury explains. For other parts of the supermarket, they used CG versions of various sets with photographed textures projected onto the digital objects.  

Matchmoving the camera from the shots filmed on the stop-motion stages was straightforward. “We had good measurements, and we didn’t have any motion blur,” Ledbury says. As they might have for a live-action film on location, the group used tracking markers, but for this film, they didn’t need to worry about removing the markers from a main plate later. Instead, because there was so little movement, they did matchmove passes. “Once the animator finished, we could put tracking markers all over the set and use those to track from,” he adds.

Lighting Passes
They also did lighting passes. For example, if a light would turn on or flicker during a shot, the visual effects team would do multiple passes of the same frame. “I could go down to the set once the animators had finished a shot and talk to the DP, and then take a couple days shooting different lighting conditions and angles,” Ledbury says. “If I didn’t get what I wanted, I could get the set back out and re-shoot. We’d have different lights coming on in the same frame so we could mix them together in compositing. I suppose I was treating this like trying to get render passes.”

The VFX crew built CG versions of four shelves to extend the set for shots in the market, adding the floor, a ceiling, and CG lights, including those the camera would have hit on a real set.

For example, to deal with green spill from the greenscreens, Ledbury would have the crew shoot two passes: one with and another without the greenscreen. “We could use the greenscreen shot for the matte, and the other, without any spill issues, for compositing,” he explains. “The compositors also had to be careful with the saturated colors because we knew the color timers would push the grade. It was quite an orange-red film; when I was in the art department, our intention was that there would be no green or blue in the film. But, that was good for greenscreen shots.”

One of the problems unique to stopmotion animation for the visual effects crew was removing animation access holes in the set. “We’d put in a foreground and shoot multiple passes of the set again. But, the sets were wood, and if they had been shooting animation for two weeks on one set, the wood would expand and move.” This was a particular problem if it was rainy or damp, which was not unusual in the UK, where they made the film.

“If we sped through the shots, we could see the set breathing,” Ledbury says. “In the morning, it dipped down, and then came up during the day. So, we had to deal with that in compositing. We’d cut out patches of shots and do 2D tracking to stabilize them so they wouldn’t bounce around.”

Initially, Ledbury thought one of the biggest concerns for the compositors would be the furry characters because hair is never easy to lift from a greenscreen background, but one advantage of having no motion blur was that it made this easier. The other was the director.

Wes [Anderson] wasn’t as picky as I thought he would be,” Ledbury says. “He was concerned about sky color, as you’d expect, but he wasn’t worried about matte edges. His main concern was with art direction. He left it to us to get the shots done.”

And Anderson’s art direction always moved toward preserving the handcrafted look of the film. Even so, as Mr. Fox proves, the most handcrafted films still rely on CG artists.