LAIKA is one of the powerhouse studios of stop motion animation, captivating viewers with films such as a Coraline, ParaNorman and now The Boxtrolls, directed by Graham Annable and Anthony Stacchi. But what audiences may be surprised to discover is that the studio also relies heavily on visual effects techniques to help realize its features. From fully CG characters to crowds and environments, LAIKA now approaches animation in a hybrid manner whilst still preserving is renowned stop motion aesthetic. We spoke to LAIKA co-visual effects supervisor Steve Emerson, CG supervisor Rick Sevy and CG look development lead Eric Wachtman about their process.Watch a clip from the film featuring the underground Boxtrolls who raise an orphaned human boy called Eggs.
It all starts with a script
“The big thing about our work is that we’re creating computer generated images to support practical stop-motion assets,” explains Emerson, who shared visual effects supervision duties on the film with Brian Van’t Hul. “First we’ll get a script and basically what happens is there’s an in-house story team here at LAIKA, and they’ll work drawing the whole thing out, they’ll create all the animatics, they’ll put all the temp dialogue and sound in, they’ll cut the entire thing together.”
With this rough cut, the film’s department heads review how the shots will be executed - almost always a combination of stop motion animation and CG and compositing approaches mixed in. “Visual effects will touch every single shot in some capacity on a LAIKA film,” says Emerson, “even for doing quality control, dead pixels or images.”
Practical solutions will be considered first. “One of the things that makes LAIKA so distinctive and so special is just the amount of effort that goes into first and foremost the animation with the puppets,” notes Emerson, “and even beyond that the incredible craftsmanship that comes out of our art department and model shop and the guys that are out there building all these physical environments. What ends up happening inevitably is we’ll hit some sort of block, where it’ll be something like water, liquid or typically something very difficult to do with stop motion - particulate effects like smoke, steam or fire.”
Although these elements highlighted by Emerson can sometimes be achieved practically (and they often are), the visual effects team is also able to generate them and help tell the story required. Sometimes a CG route is also taken for time and resource reasons. “Our typical quota for animators is something a little over two seconds per week,” notes Emerson. “We have approximately 50 stages that will be actively animated on during production. There’s only so many puppets and so many sets to go around. Inevitably as we get towards the end of a production, we just start running out of resources, and certainly that’s when they come to us, and they start leaning on us and start re-creating a lot of the physical practical assets out there and doing it all photo-real and picking up plates with greenscreen.”
So how does LAIKA replicate its practical puppets in CG? Interestingly, the visual effects team follows many of the processes that the puppet team follow in bringing the characters to life. “We’re creating the same materials that they make,” says Emerson. “An example would be the hair on the Boxtrolls, which was hemp. It wasn’t just about creating photorealistic hemp for hair, it’s also very much about how do they layer that hemp when they create the hairstyles. It was having them teach us so we could re-interpret what they were doing for the digital world.”
“They wrap the hair around the wire and then it’s posed,” adds Sevy. “So we give the same controls to our animators, we don’t run dynamics on the hair. We do run dynamics sometimes on the cloth, but just to get it started, maybe to get some keys and from there it’s posed.”
Similarly, for animation, LAIKA ensures the CG versions of the characters exhibit the same stop motion look as can be achieved for real. “One of the unique things about our rigs is that we try to build them just like the armatures are built,” says Sevy. “No spine stretches, no arm stretches. If they’ve got a ball socket here and a hinge here we animate them like that. Our puppet rigs match their physical armatures.”
For facial animation, too, the CG team marries its facial rig with the one developed to craft multiple facial piece replacements for the physical puppets which are printed with a powder-based color 3D printer. “We’re working with the rapid prototype animators that are doing all the physical facial animation,” says Emerson, “and they’re setting the looks in terms of those expressions for those animators on our side and beyond that when we do have 20-30 standard expressions in addition to the phonemes.”
That same stop motion approach exists even for crowd animation, something that might be considered optimal for a CG effect. LAIKA’s effects team typically added in additional Boxtrolls and other characters to scenes in the film, all the while ensuring that the hand animation style remained. “I remember when we first started putting together some of these crowds on ParaNorman,” recalls Emerson, “we were looking at the stop motion aesthetic in terms of animation on a technical level. What is it that makes it look like stop frame? We did all kinds of stuff where we messed with animation curves, we pulled frames out. Ultimately what we learned going through that process is that it’s not anything that’s technical, it’s a creative eye thing. We’re fortunate that the keyframe animators we have in visual effects - a lot of them have stop motion backgrounds, so they’re able to consistently deliver that to us.”
LAIKA did experiment at first with a Massive solution for crowd work, but soon realized that a full AI crowd system was not necessary. “Our shots were pretty short,” says Sevy, “so we could get away with, ‘Here’s a bunch of characters around a market stall, let’s animate them for 200 frames, and bring them together with different walkers for keyframe.’”
What did help the team, however, was motion capture for some of the characters, cleaned up and augmented with keyframing. “We animate everything on 1s and they’re gunning for everything as a naturalistic look with the animation,” explains Emerson. “Again it goes back to when we were banging our heads against the wall trying to figure out what the stop motion look was, we thought maybe it’s not so much about pulling frames or tweaking curves, the guys across the street are gunning for something very naturalistic - let’s start there. And I think that was one of the big motivators for bringing motion capture into the mix.”
“For crowd scenes,” adds Sevy, “our rigger developed some layout tools that the modelers could use. The modelers laid out the crowds, these are the mocap cycles we want applied to them, then they just played with timings and off-set and layout until the art directors bought it. If there was a character that seemed out of place or close to frame, we would up-res it to a keyframe character and pass off to a keyframe team.”
The result is that in many scenes in The Boxtrolls are combinations of practical photography and CG characters. “There’s an iconic shot of the Boxtrolls standing fairly close to camera clapping on their boxes,” relates Emerson by way of example. “In that case, there are three practical and the rest were all computer generated. Typically the rule is that the hero puppets and hero characters are usually practical. When it comes to a crowd, those second row back are the ones that we do in CG.”
Crafting the scenes
In addition to CG puppets, LAIKA’s visual effects for The Boxtrolls extended to environments, props, 2D fixes, paint-outs and filling out the scene. The studio has been fine-tuning its pipeline over the past few films to help make the CG characters and environment work integrate flawlessly with the photographed world.
Stop motion animators shoot with a single Canon 5D Mark III on a flyer to enable stereo acquisition. “We take the left eye, shift over a little bit and shoot the right eye,” explains Sevy. “The camera is typically done motion control programmed ahead of time, so the animator will pose the puppet, shoot the frame, we’ll index to the next frame and then they’ll pose it again.”
To help the visual effects team with tracking and lighting their CG additions, an artist will then survey the same stage. “We’ll go in and reset that move and mark up the stage with little orange markers for us to track,” says Sevy, “and we’ll run that move again so we have a tracking pass. We’ll also drop in a little HDR rig and capture the lighting setup on that stage.”
A stage will also be set up to shoot a practical puppet on a turntable to acquire lighting, stage lighting and photographic textures for the CG versions - to be directly compared side by side during lookdev. “We build our Boxtrolls in kits,” explains Wachtman. There’s an ‘A’ set of arms, a ‘B’ set of arms et cetera. We scanned those and built those. You mix and match those parts and you can get 80 different Boxtrolls.”
LAIKA utilizes 3DEqualizer to track a virtual camera for the shot. Notes Sevy: “Most people think, ‘Hey you’ve got the motion control move right, so why do you need to build the digital camera?’ But the mechanics of the whole arm - you get sag and things - so the move never happens the way you program it.”
“At times we also go in and have a photogrammetry step where we shoot other pictures,” adds Sevy. “It’s part of our camera solve step. We grab some other reference photos, string those together and pipe them through OpenCV to generate a mesh, which gives the CG animators a ground plane and environment they can animate their puppets on.”
Matchmoving the camera move and animated objects in the scene is crucial, since a number of other elements will be added in CG. “Some of the rain hits on Snatcher at the opening sequence were CG,” states Wachtman. Bugs crawling across the trolls are all CG so that required a tighter matchmove - that’s part of our camera matchmove and puppet track.”
For their HDRs, LAIKA has the benefit of the animation stages being available for some time. “So if the HDR is not working we can go back and shoot another one,” says Wachtman. “Or we can shoot four or five of them. Our HDRs are ridiculously extensive - we go down to 1/8,000 of a second and ISO 50 - there’s a lot of range in there. We shoot from four or five different places and reverse engineer where the lights came from, and do HDR blending, which is something we did on ParaNorman where characters walk through multiple HDRs. We also shot on this film some stock light HDRs where the camera points directly into the light and onto some geometric cards to get some of the right fall-offs.”
LAIKA carried out around 300 set extension shots for The Boxtrolls, often modeling buildings as hero assets shot for shot to match the practical ones. “There was so much detail in those buildings that we pretty much spent hero asset time building hero buildings,” notes Wachtman. “If there were water marks that needed to be painted in, we painted them. They might be using some weird plaster speckle and we had to put all that in there.”
In one scene from the film as the characters are sliding down the roofs of some houses and breaking off tiles, a hybrid practical and CG approach was used. “All that stuff was animated practically and cleaned up, but then it’s really anything beyond that - all the additional buildings that are up for grabs,” explains Emerson. “It comes down to what are resources of the stages. Once they leap off of the edge and are sliding down the rooftops, basically the roof themselves are practical but everything you see there is picked up and we finished it off in visual effects.”
Lighting and rendering
Although LAIKA employs a typical VFX pipeline, making use of Houdini for effects, Katana for lighting, RenderMan for rendering and NUKE for compositing, the studio has to work within the scope of the practical animation. “The effects we do are not necessarily photoreal effects and we’re not making CG films either,” says Emerson. “It’s highly stylized. An example is the fog elements that are whipping by - we’re not going to do just straight atmospheric fog. We’ll go through look development cycles with the art department. A lot of times we’ll build practical interpretations of how they’ll do things in-camera. “
“I come from an old school PRman base, so physically plausible was really limiting,” adds Wachtman. “Shading on these films is really different. Hair is a really good example. They use hemp - they glue it and shade it with hairspray and it’s two sided. So we can’t just go out and use the most amazing hair shader algorithm. Super-glued hemp! There’s only so much you can do. A lot of times that breaks plausible. There’s not really a shader that does that.”
“On Coraline,” notes Emerson, “stereo was such a pain, but now the tools have come so far. We leaned on OCULA a lot in this show. There’s a stereo script completed up front that the guys on the stage stick to, but sometimes they’ll shoot a foreground for something and then the background won’t be scheduled to shoot for a year, and then they might not know what the IO is and we end up with something too deep. So we go to OCULA. Our filmmakers are really careful about how they’re using stereo. Personally, I do like the idea of looking into a world as opposed to it reaching out to grab you.”
A signature scene: the Mecha-Drill
In one of the film's biggest sequences, the pest exterminator Snatcher uses his Mecha-Drill to dig into the Boxtroll's cavern. LAIKA built several drill puppet rigs for the shots which were each over five feet tall and weighed more than 75 pounds, comprising 600 pieces of metal, plastic and steel, something Emerson describes as "one of the largest puppets that’s ever been made for a stop motion film." With a deadline looming, the visual effects team also stepped in to re-create the Mecha-Drill and its impact on the cavern with CG effects.
The drill was always going to be built in CG in any case for matchmoving, since a number of Boxtrolls hang off of it. In addition, the CG version was able to spin and help generate a waft of effects animation. "For the Mecha-Drill we had to add this dense, sooty, rancid, black smoke," says Emerson. "A lot of that was run through Houdini."
Ultimately, LAIKA’s team of around 60 visual effects artists were able to carry out an eclectic array of shot work that included more than just hero CG animation. “We do a ton of plate reconstruction and cosmetic work on the puppets,” says Emerson, “so a good half of that team is fully 2D, cleaning up puppets, taking out rigs, doing the comps. One of the gags is that it’s like Noah’s Ark over here - two animators, two lighters, two effects guys and so on!”
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