The Hybrid World of The Boxtrolls

The Boxtrolls

The Boxtrolls was the third feature to come out of Oregon-based animation studio LAIKA, both of whose previous productions Coraline and Paranorman were Academy Award nominees for Best Animated Feature Film. I covered the film’s innovative blend of stop-motion animation and visual effects in 2014 on the Cinefex blog, and I’m pleased to republish the article here at The Illusion Almanac.

Directed by Anthony Stacchi and Graham Annable, and adapted from the book Here Be Monsters by Alan Snow, The Boxtrolls tells the story of Eggs, a human boy raised by Boxtrolls — strange cavern-dwelling creatures who live in hiding beneath the cobbled streets of Cheesebridge. When Eggs meets Winnie, feisty daughter of Cheesebridge dignitary Lord Portley-Rind, the upper and lower worlds collide and the sinister truth behind the dastardly Archibald Snatcher’s mission to exterminate the Boxtrolls is revealed.

Like its predecessors, The Boxtrolls is at heart a stop-motion feature. However, thanks to developments in both methodology and filmmaking technique, it is described by LAIKA as a “hybrid” film integrating the traditions of stop-motion with the latest advances in visual effects.

  • “The Boxtrolls” is a hybrid animation film with its roots firmly in the stop-motion tradition.
  • Michael Hollenbeck animates Archibald Snatcher and the Red Hats.
  • David Pugh animates fallen fruit in the expansive marketplace set.
  • Danail Kraev animates the Eggs puppet in a Cheesebridge street set.

Coraline was almost entirely shot in camera,” explained LAIKA visual effects co-supervisor Steve Emerson. “There is some CG in that film, but for the most part the director, Henry Selick, was after something entirely practical and in-camera. The big shift for us came with Paranorman. That’s when our producer and lead animator, Travis Knight, started talking about this vision of creating hybrid films.”

In the LAIKA lexicon, hybrid filmmaking means taking a stop-motion film and expanding it visually beyond the confines of the animation stage. “As a genre, stop-motion is typically confined to smaller environments and a limited number of characters,” said Emerson. “With hybrid, the idea is to use technology to open up these worlds, and do things that you wouldn’t typically do in stop-motion, like have large crowds, or big effects, or wide vistas.”

CG “extras” were used to swell the ranks of stop-motion characters in crowd scenes.
CG “extras” were used to swell the ranks of stop-motion characters in crowd scenes.

Detailed planning was key to the successful combination of stop-motion and CG, with decisions being made early in the preproduction process. “The department heads huddled up in a conference room and went through the film shot by shot,” Emerson recalled. “We figured out who would build what: what was going to be practical and what was going to be CG. Typically in those meetings, I would let them try and figure it out practically first. When they hit walls, that’s when the room would turn to me.”

While CG was frequently employed to realise shots that were not technically possible using practical techniques, it was also essential in covering resource gaps. “At the full height of production we have about 50 active stop-motion animation stages,” commented Emerson. “The weekly quota for each animator ranges from two to four seconds. But there are only so many puppets and so many sets to go around … and a lot of work that needs to get done. That’s where we step in.”

The in-house visual effects department benefited from close integration with the rest of the production. “I came out of live-action visual effects,” Emerson reflected, “and I was used to angry effects artists who got a whole bunch of footage that was shot months ago, with greenscreens that you couldn’t do anything with. The great thing about LAIKA is I get to sit in a theatre with the other department heads and be critical of things before they can even start launching. I can ask them to adjust lighting on greenscreens, or do multiple exposure passes. In can ask them to use invisible UV paint in order to get mattes off characters. It’s a big, big advantage, and it allows us to move through a lot of inventory with a relatively small team.”

“Because we have controlled sets and the sets are up for so long, we can go in there and get pretty much perfect stereo HDR data,” added CG look-dev lead Eric Wachtman. “We basically survey every set, so we can get all the information we need. That makes lighting on the CG set pretty painless.”

For the most part, the LAIKA visual effects team uses off-the-shelf software. “For shading and lighting, it’s all RenderMan,” said Wachtman. “We use Katana for our lighting pipeline, and Maya is our main modelling software. We use Nuke for compositing. We have some other special stuff, too, and we write a lot of our own tools and shaders.”

Despite the close parallels with live-action visual effects, the stop-motion aesthetic poses its own unique challenges. “On a traditional visual effects film you’re matching reality,” Wachtman remarked. “On ours, we’re matching something that’s miniature, but not really supposed to look miniature. Cloth isn’t really cloth. Hair isn’t really hair.”

“If they’re creating hair from hemp, it’s not just about us creating photoreal hemp,” Emerson elaborated. “It’s also about figuring out exactly how that hair is being layered. Also, everything is intensely art-directed. For the skies in The Boxtrolls, they built practical sky rigs out on the set using cheesecloth, and so on our side it’s not just about painting and creating clouds, it’s about creating cheesecloth clouds. We’re doing photoreal visual effects, but they’re heavily stylised. They’re never just out of the box.”

The Boxtrolls

As well as looking identical to their practical counterparts, the CG characters of The Boxtrolls also had to perform in the same way. “We report to the animation director,” Emerson asserted, “the same as the animators on the stages. So we’re all showing it to the same guy to make sure that everything is uniform. When we do facial animation, we work with the head of the facial animation team.”

In order to give its stop-motion characters the widest possible range of emotions, LAIKA employed face replacement. Using a rapid prototyping system, thousands of face parts were printed for each character — more than 53,000 in total for The Boxtrolls, 15,000 of which belonged to Eggs. In combination, these gave the film’s hero over 1.4 million possible facial expressions.

Stop-motion face replacement brings a discernible granular texture to close-up shots. Matching this in CG proved challenging. “The texture of the face changes, but not every frame,” commented Wachtman. “Sometimes the animators will hold it for two or three frames before they switch to a new face, and you definitely feel that when you watch the film. We wanted to incorporate that granular feel into our CG puppets, so we wrote scripts to deal with it.”

It was critical that the CG characters in “The Boxtrolls” be indistinguishable from their stop-motion counterparts.
It was critical that the CG characters in The Boxtrolls be indistinguishable from their stop-motion counterparts.

The majority of the faces were made in two parts, so that every frame in which they appear required digitally fixing to conceal the joins — a task requiring considerable manpower. “We have a team of about 20 artists, and we’ll expand to a team of 60-70 when we’re fully ramped,” said Emerson. “About half those artists are doing purely cosmetic work on the plates. That includes seam removal on the puppets’ faces and also rig removal, because obviously the animators can’t defy gravity out there.”

Additional cosmetic fixes were needed to repair the environments. “The animators have to physically tie down those puppets, which means drilling into the sets and screwing down their feet. By the time they’re done animating a shot, you end up with a set that looks like somebody’s gone in with a Tommy gun and shot the place up!”

The time-consuming nature of stop-motion brought further need for digital repair work. “The shots take weeks and weeks to animate,” commented Emerson. “Over the course of those weeks, the temperature of the set is changing, so even though we’re doing motion control, the plates don’t always line up. The guys in our paint department are really the unsung heroes — if they’re doing their job well, nobody knows they’ve done anything.”

The Boxtrolls

The hybrid approach taken by LAIKA for The Boxtrolls is exemplified by the ballroom scene, in which Eggs accompanies Winnie to a grand society ball hosted by her father, Lord Portley-Rind. During the sequence, the camera sweeps past stop-motion puppets dancing in the same frame as their CG counterparts, all within the opulent ballroom surroundings.

To realise the sequence, the hero puppets were animated by hand in the miniature ballroom environment, in front of a motion-controlled camera. For each frame, a beauty pass was shot, after which a greenscreen was lowered into the set behind the puppets, the lighting was adjusted to create a strong silhouette and a second frame was shot as a matte pass. For some shots, additional frames were photographed at the same time to capture interactive lighting effects. The greenscreen was then removed and the lighting restored to its beauty configuration, allowing the animators to move the puppets ready for the next frame.

“The plates ended up being hero characters in hero lighting, with greenscreen frames chasing them through the environments,” said Emerson. “Then we went in and populated the rest of the frame with additional CG dancers.”

A similar approach was used for broad action scenes, such as the chase sequence in which Archibald Snatcher drives frantically through the streets of Cheesebridge, while Eggs and his Boxtroll friends slide perilously across the town’s rooftops. “Where the characters are landing on roofs and kicking up tiles, all that is hand-animated and in-camera,” revealed Emerson. “The rest of those environments — the hundreds of other buildings, the landscapes, the skies and the fog — all of that is computer generated.”

Atmospheric effects contribute significantly to the film’s Victorian ambience, and were largely provided by the visual effects department. “Fog is a tough thing to get in camera, so it makes the most sense for us to deal with it,” Emerson commented. “We had a long look-dev cycle working hand in hand with the art department and the rigging and camera teams, looking at how they would approach it in camera. It’s about creating a fog that represents this very distinct artistic language. We use a CG fog system, but there’s a lot of animated cheesecloth blended in there too!”

The Boxtrolls roof chase breakdown, showing the hybrid use of stop-motion animation and visual effects.

One way or another, the LAIKA visual effects department touched every frame of The Boxtrolls — some 1,200 shots — ranging from simple dead pixel clean-up through to elaborate character and environment work.

Reflecting on his department’s contribution, Emerson said, “I feel that most people look at LAIKA’s films as animation; and when they think animation, they don’t always think live-action visual effects. That’s one thing I want to put out there for the visual effects community: that the people working on these shots are all people with live action visual effects backgrounds who are working in a live-action photoreal effect environment. And it’s very, very difficult stuff to do!”

This article first appeared in slightly different form on the Cinefex blog. Content copyright © Cinefex 2014. Photographs and video copyright © LAIKA, Inc. and Focus Features, LLC. Special thanks to Fumi Kitahara.

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