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Issue: Volume 35 Issue 5: (Aug/Sept 2012)

One Frame at a Time

By: Barbara Robertson
The good news is that the visual effects crew working on Tim Burton’s Frankenweenie didn’t need to create CG characters that matched puppets for the stop-motion film or remove seams from puppet faces. The bad news—or the interesting challenge, if you prefer— is that they still ended up producing 1200 visual effects shots.

The reason was unique.

“With every stop-motion film, much of the work, like rig removal, is hidden,” says Visual Effects Supervisor Tim Ledbury. “The difference between Frankenweenie and other films was the scale of the puppets. They had to be big because of the mechanics in Sparky [the dog]. And that meant we ran out of stage space. So we had to do more digital environments.”

More, as in nearly everything. The sets included houses for the main character and a neighbor, and the school. “Everything else is CG,” Ledbury says, “houses, streets, lampposts, cars.”

A crew that topped 40 artists at peak worked for more than two years on the show creating the environments. They also swam invisible fish through digital water, cast light from torches and flashlight beams, ignited various electrical effects that appear throughout the film, and burned a windmill with digital flames. Of the 1200 visual effects shots, only around 200 had rig removals alone.

 Skies painted by visual effects artists lifted the storytelling into the environment.

Size Matters


The stop-motion animated feature, a remake of Burton’s 1984 liveaction short, stars a young boy—a child scientist named Victor Franken stein (voiced by actor Charlie Tahan). It’s a parody of and homage to the 1931 film Frankenstein: When Victor’s dog Sparky dies in a car accident, Victor revives him.
“The story is based on something so dear to Tim [Burton],” says producer Allison Abbate, who has produced numerous animated films and worked with Burton on Corpse Bride. “It was born of a time when he lost his beloved dog. And, he loved horror movies.”

In the animated feature, Victor is an outcast. Sparky is his only friend. “The whole film is about a boy and his dog,” says Supervising Animator Trey Thomas. “It’s about the purity of their relationship. Victor drives the story. But, Sparky is Victor’s reason for doing all the stuff that gets him into trouble.”

All the puppets are silicon with mechanical steel armatures inside. The animators performed the puppets on “ones,” that is, they moved the puppets into unique poses for each frame; 24 poses for each second of film. Sparky determined the scale.

“You base the scale on the smallest important actor,” says Rick Heinrichs, production designer. “And that was the dog.”

Although “revived,” Sparky still acts like a dog in the film. He isn’t an anthropomorphic character or a monster. “Tim wanted a dog that was dog-like, and to get a happy, charming little guy with personality was a real challenge,” Thomas says. “The animators had to make this little puppet that has only dog emotions come off like a living thing. We had to make him larger to get expressions.”

To fit Sparky with an internal armature complex enough for these precise performances, the puppet needed to stand three-and-a-half inches high from his head to his toes, and five inches long. That meant the boy Victor was a foot tall, and Victor’s parents grew to 16 to 18 inches tall.

“So when you do a house scaled to a character that size, you’re talking about a fairly large house,” Heinrichs says. “And we had a whole neighborhood.”

More than one whole neighborhood. During production, individual animators worked simultaneously on 35 sets. Thus, the neighborhood became the province of a visual effects crew that created set extensions and, for some wide shots, an entire digital town. “We had 800 greenscreen shots,” Ledbury says. “And, we had different scales of miniatures that we had to comp.”

In one shot, for example, a Godzilla-like turtle monster stomps on a miniature of the town center, and crowds of puppets run away. “We decided to make the miniature go with the turtle and composite puppets shot on greenscreen for the crowds.” To rotoscope the puppets, the artists used The Foundry’s Nuke and Autodesk’s Maya.

The crew also used Maya to build the town, creating a “New Holland” kit based on 18 house styles. “This is suburbia,” Ledbury says, “clean, flat, and boring. So you’d immediately say it would lend itself to CG. But, it only makes it look more CG and stark. We added a bit of grime and wonkiness. Threw in a few trees. Put water stains on the buildings.”

Textures and set dressing changed the look of individual streets. “We had the real houses on set to follow in terms of style, and we photographed swatches and material samples from the art department, as if we were doing a fantasy liveaction film,” Ledbury says. “We clipped sections of streets together, put a curve in the road, added a junction, and dressed the streets with bushes, trees, cars to change the look.”

When the camera was higher, the crew composited lower-polygon versions of the town. For a wide view from the windmill on the hill, the artists put mountains behind the CG town. A rooftop shot also needed a big environment extension.

“It’s a shot with a kid on roller skates on top of a roof,” Ledbury says. “They built only one side of the roof, so we extended that, too. He’s doing experiments with fizzy water. We had to do fluid simulations, and CG spray and steam coming out of a bottle.”

Water and fire are never easy to simulate with computer graphics, and this film has both. In stop motion.


Top Left to Bottom Right across: VFX artists built much of New Holland with CG. Victor in his attic preparing to revive Sparky. Tim Burton, puppet master. Sparky the dog established the scale.

Frame-by-Frame Sim


At one point in the film, Victor shines a flashlight beam into water to highlight an invisible fish. “That was harder than it sounds,” Ledbury says. “It took a lot of versions before Tim [Burton] picked a final one.”

Creating a fluid simulation with stopmotion characteristics was difficult. To shine a light on the water rippled by the invisible fish, the crew blended rendered passes of the water. But first, they had to create the water.

The effects artists started with a CG fish and a water simulation created with Next Limit Technologies’ RealFlow software. “We simulated the fluid really slow, brought the meshes into Maya, and roughed them up,” Ledbury says. “Sometimes we tweaked the mesh by hand to get rid of perfections. We might plus two frames together and get a jump. We’d change the order of the frames. There weren’t many procedural ways to do this, so we did it by hand.”

Similarly, it turned out that there were no procedural ways to create the electrical effects and the lightning.

Throughout the film, lightning shoots through the sky and electricity dances across metal objects. When Victor revives Sparky, the entire attic becomes electrified.

“There are lots of ways to create electrical effects with CG, but you can spot them,” Ledbury says. “We wanted something that would fit more into the stop-motion look. So, we painted all the effects frame by frame for something like 100 shots.”

In other words, they achieved the stopmotion look by mimicking the technique, by moving the electricity frame by frame. “It was quite painful,” Ledbury says. “I did a couple myself, and it drives you up the wall. But the results are head and shoulders above the standard approach. A group of four or five people had a go at it and got the right look. By the end of production, they could do a shot the first time. They got used to how fast the electricity should move.”

Burning Windmill


Sitting on a hill above the town is New Holland’s monument, a wooden windmill. At the end of the film, it catches on fire and collapses. “Those were the shots that kept me awake,” Ledbury points out. “We were all concerned about how we would achieve the fire. We toyed with using live-action elements, but in the end, we went full CG using Maya Fluids.”

The animators used windmills in various sizes appropriate for shots ranging from closeups to wide shots. For example, one full windmill used for wide shots stood four-and-a-half feet tall; a separate top was in puppet scale. There were interior sets, as well. The visual effects crew built CG versions of each set using surveys for measurements. Then they match-moved the sets and camera positions in the final images with CG versions and CG cameras to position the fire in approximately 60 shots.

“We’d talk to an effects TD, decide where the fire should go, lay it in, tweak it, and enhance it,” Ledbury says.

The effects TDs started by using Maya Fluids to simulate several versions of fire, for three shots to start, giving Burton options to consider before settling on a final look. “His main concern was the speed of the fire,” Ledbury says. “We started too slow. Faster fire put more energy into the scene.”

Once the fire was in place, the artists layered in other CG elements, such as falling debris, bits of digital wood, planks that hit the wall and splintered, and smoke. “For smoke, we went half and half,” Ledbury says. “Smoke is notoriously difficult to get to work in CG, even when you have all the time and money you need. So, we enhanced the CG smoke with live-action elements. Then to develop that Frankenweenie look, we tweaked. The fire took a lot of tweaking. It was weeks of pain.” At the end, with all the elements rendered out, compositors could drop out frames for a final bit of tweaking as needed.

One of the most challenging windmill shots moved into the visual effects department after all the sets were gone. “They filmed the puppets against greenscreen, and we built a CG interior, part of the windmill exteriors, and the sail,” Ledbury says. “We couldn’t use a previous image of the set because we needed to have flickering light from the fire. I hope no one can tell.”

The effects crew also put fire into CG torches held by a crowd of puppets that chase Sparky through a CG town. They tracked each torch in the crowd and inserted fire in the appropriate scale. And, they tracked in 3D flashlight beams for shots in a pet cemetery. “Doing five of those shots would have been fine,” Ledbury says. “But we had 20 torchbeam shots in a misty scene with lens flares.”

Shine a Light


Although Frankenweenie is a black-and-white film, the artists worked in color. “The art department painted some of the sets in black and white, and some in color,” Ledbury says. “The grass is green. But the matte painters worked in color for their own sanity.”

This was true for the skies as well as elements on the ground. “We created a whole raft of assets for the artists to study,” says Heinrichs. “In a movie like this, the sky is an important character; it’s part of the storytelling process. The people who did the backgrounds were incredibly skilled at extending the look and feel into the environment.”

Without color to put depth into a scene, the artists needed to experiment with the tone. “People soon learned what would happen when they went to black and white,” Ledbury says. “They could apply the black-and-white lookup as they went along, but by the end of production, it wasn’t an issue. We all kind of forgot whether we were working in black and white or color. It was just the movie.”

Digital environments and set extensions, water, fire, and smoke simulations, electricity, rotoscoping, greenscreen shots, match-moving, compositing. It all adds up to Ledbury calling Frankenweenie an effects film. “I think we had close to 800 more visual effects shots than we had on Corpse Bride and twice the shots I worked on for Fantastic Mr. Fox. It worked out to between 600 and 700 shots per year, which is a lot for 40 people, but we pushed through. We had to be quite fast and efficient. We didn’t have a massive technical infrastructure.”

But, the approval process was quick. “We were quite low on layers of management,” Ledbury says. “We didn’t have CG supervisors or a compositing supervisor. It was just me. And, I went directly to Tim.”

Ledbury has worked as a visual effects artist on several live-action films as well as stopmotion features, and he finds himself drawn to the stop-motion world.

“It seems to be more special in a way,” Ledbury says. “The process is grueling. Compared to six months on a live-action shoot in Soho, 70-odd weeks on a shoot can wear you down. But the end product can be more satisfying. The shelf life of some live-action films is short. This feels like something that might last. And, the artists at this studio have more ownership, as well. We can wander around at lunchtime and have a look, see the puppets in the workshop. It’s a lot of work. But it’s fun.”

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