Charted across raging seas, bam-boo jungles, and mountain ranges ravaged by howling blizzards, a little boy’s journey of self-discovery in Kubo and the Two Strings whisks audiences away to something never before seen in the history of cinema: a stop-motion epic.
For Oregon-based Laika, the ground-breaking studio behind Coraline, ParaNor-man, and Boxtrolls, the film represents the culmination of a decade pioneering its unique amalgam of rapid prototyping (RP), live-action puppetry, motion control, and state-of-the-art CG. Not only has Laika’s “hybridized” form of filmmaking liberated stop motion from its “tabletop” feel, but through new advancements in RP, it can now draw increasingly subtle, heart-wrench-ing performances from a simple, resin- based face.
Like a work of cinematic origami, Kubo and the Two Strings folds together cinematic and literary influences once far afield from the world of stop motion. Set in a mythical ancient Japan, the story follows a boy named Kubo as he cares for his ailing mother in a high, clifftop cave overlooking the sea. There, she regales him with stories of his late father, Hanzo, before slipping into deep spells of sorrow cast by the rising moon. Pining for his warrior father, Kubo ventures each morning into the village square and captivates the crowds with his over-idealized fantasies of Hanzo’s exploits in battle, all of which he brings to life with folded origami at the strum of his magic shamisen.
In a failed effort to commune with his father, Kubo visits the cemetery during the Obon festival honoring the dead, and casts a rice-paper lantern onto the lake. Hoping to guide his father’s spirit home, he instead un-leashes the vengeful spirits of his mother’s two sisters, who come screaming from the skies to settle an old vendetta harbored by Kubo’s grandfather.
Alone, running for his life, Kubo is soon joined by Monkey, a motherly simian voiced by Charlize Theron, and Matthew McConaughey’s Beetle, an insect samurai who takes up the boy’s mission in a flush of knight errantry. Together, they set out to banish the Sisters by finding three treasures left behind by Kubo’s father. To fulfill the quest, they must brave a gauntlet of perils that include the blizzard of the Far Lands, the monstrous skeleton guarding the Hall of Bones, a raging sea storm and the under-water Garden of Eyes, and the horrifying Moon Beast – a luminescent reptile that worms through the sky and became Laika’s first fully rapid-prototyped character.
Kubo’s only weapon on his journey is his shamisen. With a strum of the strings, a ripple of magic emanates outward, animating his origami into a menagerie of living paper wonders: a flock of birds, a giant chicken, a miniature samurai Hanzo that guides his way. Indeed, the film is not only a love letter to the art of animation, but to Japanese culture itself, where every frame is freighted with references to Noh theatre, origami, ukiyo-e, and Edo-period doll making. Most importantly, the design of every character, prop, and envi-ronment in the film is simplified and textured to reflect the modest, graphical aesthetic of Japanese woodblock printing, particularly that of artist Kiyoshi Saito.
KUBO’S MAGICAL SHAMISEN BRINGS TO LIFE ORIGAMI, WHICH TAKES MANY FORMS, INCLUDING A FLOCK OF BIRDS.
Saito’s process involved placing a drawing over blocks of wood, carving out a relief of lines, and using the blocks to create an impression on paper, usually in a muted color palette. He would also integrate the texture of the wood grain into every painting, a practice Laika’s production designers and CG artists diligently followed.
“We painted the pattern into every single asset we made,” says CG look development lead Eric Wachtman, “right down to the cloth on some of the digital characters. We used [The Foundry’s] Mari, and also made a procedural version of it in [Pixar’s] RenderMan.”
Saito’s graphical shapes and bold abstractions not only inform the set designs, particularly the angular design of Kubo’s seaside cliff, but the designs of the characters as well, whose striking silhouettes, redolent of Japanese manga and Hayao Miyazaki’s characters, had to be instantly readable against the stark, sprawling expanses of sea and snow.
However, honoring this aesthetic in the characters, particularly Beetle and Monkey, baffled current color RP technology, which couldn’t cope with the intricate, hard-edged designs. Furthermore, Knight was seeking a level of subtlety and nuance in the facial performances far beyond anything Laika had ever attempted. This would entail printing thousands of colored expressions for the mouth and brow to reach the millions of possible facial expressions needed for a finely calibrated performance.
While Kubo was in development, the only color 3D printer on the market was 3D Systems’ Z650, a powder/gyp-sum-based printer Laika used on ParaNorman and Boxtrolls. It could be used for the human characters in Kubo, says Director of Rapid Prototyping Brian McLean, but not for Monkey, Beetle, and the Moon Beast.
“We would have to find a new technology to achieve the director’s vision, or force a redesign of those characters to soften those hard edges,” he says.
For McLean and Technical Director Rob Ducey, the latter was not an option.
Alternatively, Stratasys – whose plastic, non-color polyjet printers had been used to cast Coraline’s hand-painted faces – was beta-testing the Connex3, the first color multi-material resin printer. Alas, it could only print three of five colors: white, black, cyan, magenta, and yellow.
“So right off the bat, we were running up against serious limitations in the way color was assigned,” says McLean.
THE INTRICATE, HARD-EDGE DESIGN OF SOME OF THE CHARACTERS, SUCH AS BEETLE (ABOVE), REQUIRED NEW 3D PRINTING TECHNOLOGY.
Furthermore, Stratasys’ bundled printer software limited how those three colors could be mixed – a problem for Laika, which had grown accustom to painting detailed, gradated textures that could be jetted down onto a powder substrate. Still, the new plastic polyjet technology was so proficient at printing – with unfailing repeat-ability the fine feature details of Monkey’s face and fur, the Moon Beast’s lamellar body, and the sharp nose and hard facets of Beetle’s armor-like head – that the benefits far outweighed the drawbacks. The RP team’s only challenge was color matching the conceptual art.
To that end, Laika bypassed the bundled software and had expert 3D printing engineer Jon Hiller develop custom slicing software that would allow for gradient shading and fine color details. Hiller’s new driver could output a giant 3D bitmap that told the printer where to place each microscopic droplet of cyan, magenta, yellow, black, white, or clear resin in the exact proportions to replicate the color of the digital model. Hiller also improved Stratasys’ color model by equating and indexing specific ratios of 3D resins with their real-world measured color.
“The final hurdle was convincing Travis [Knight] that the faces of Monkey and Beetle could be simplified to three colors,” says McLean.
Initially, there was some fear that the subsurface scattering of the Z650 powder-based humans might seem incongruous next to that of the resin-based creatures, by the way light reflected, refracted, and raked across their faces (the Z650 printer jetted down color a sixteenth of an inch into the powder substrate).
The fear proved unfounded, however, when they discovered the UV-cured resin of the polyjet technology was inherently translucent. The subsurface scattering of Monkey and Beetle has a similar quality to Kubo, even though they’re made out of plastic.
The Connex3 produced thou-sands of high-resolution color sculpts for Monkey and Beetle, providing over 13 million possible facial expressions for Beetle and 30 million for Monkey. In total, 15,581 faces were made for monkey on the Connex3, while 23,197 were printed for Kubo on the Z650.
No matter the printer used, the head-modeling process always began with scanning a clay maquette into Autodesk’s Maya. Then, modelers refine the topology in both Maya and Pixologic’s ZBrush before sending it to the printer. After incorporating subtle artistic changes from Knight, the modeler simplifies the geometry in PixelMachine’s Topogun and decides where to split the mouth and brow, while riggers outfit the face with simplified facial controls for shaping the expressions.
Working in Maya, the CG modeler then collaborates with the fabrication lead to engineer the internal components for the head. “This means [Laika’s modelers] have all the problems of modeling for a CG production, along with a myriad of concerns stemming from creating a physical object: minimum material thicknesses, printer resolution, mechanical tolerances, and so forth,” says Lead 3D Modeler Ty Johnson. “The majority of a modeler’s time is spent breaking the head into over 70-plus mechanical parts that have to fit into the head the size of a golf ball.”
Because 3D printing files have always been polygonal, Laika’s RP department has found Maya perfectly suited for handling both the soft- and hard-modeled geometry, and ensuring they function together.
Next, a small group of digital animators fashion the vast digital library of expressions used throughout the film. Then, animators are assigned shots in the film, for which they pull shapes from the pre-existing library or create special expressions and send a Maya Playblast of the facial performance to the editorial department. If approved by the director, the CG animator compiles the list of faces for the shot, requesting pre-printed expressions be pulled from the physical face library and sending the special expressions off to the 3D printer. Once printed, the faces are cleaned, sanded, and tested before delivery to the stage on the day of the shoot. Because Knight was demanding such a finely pitched acting style, tending to these “special expressions” became an almost unending occurrence.
“On Coraline, our job was creating different phoneme shapes to string together for lip syncing,” says McLean, “but over the course of the last few films, it [became more] about very subtle acting and getting as much emotional range from these little puppets as possible. We’d provide Travis with Playblasts, and he’d kick them back with acting notes asking, for example, for a slight tilt in the brow. Our pipeline wasn’t designed for this level of scrutiny. It was designed for building a library of hundreds of faces in advance that could be delivered to the set and reused over and over. So sometimes we didn’t have the correct expressions in the predetermined kits, which forced us to go back into Maya, and animate and print faces especially for the shot.”
In keeping with this push for greater emotional range, a face was no longer animated every other frame, like on ParaNorman, and instead changed expressions 24 frames per second. Moreover, the animators shaped the main characters’ performances from a reference bible that borrowed from some of the finest acting touchstones of our time.
THE MOON BEAST
While the RP department was able to deliver textured puppets for Kubo, Beetle, Monkey, and almost every other character in the film, bringing the Moon Beast to life required more than advanced voxel printing. The Connex3 forged 130 parts for the snake-like fish, including the intricate lamellar scales, the armor-like plating, piranha-like teeth, and spinous dorsal fin. But achieving its eerie, turquoise luminescence demand-ed an intricate dance between RP, visual effects, compositing, and the skills of Director of Photography Frank Passingham.
NEARLY EVERY STOP-MOTION SET IS PAIRED WITH A CG EXTENSION FOR AN EPIC FEEL.
Emerging at the climax, the Moon Beast slithers across dark, swollen skies like some serpentine poltergeist, descending fangs-bared upon Kubo as he flees through the village. Though Visual Effects Supervisor Steve Emerson and Composting Supervisor Peter Vickery could have created the effect digitally, the potential for inconsistencies between the miniature sets and puppets, let alone betraying the Herculean effort involved in rapid-prototyping the entire character, demanded a solution that was more faithful to the film’s practical roots.
“We ended up realizing there was no reason we had to photograph this puppet under one lighting scenario,” McLean reveals. “We could shoot the puppet under multiple lighting scenarios and give those passes to the VFX department, which could then pull masks and composite various looks together.”
Although the Moon Beast’s concept art features shades of jade and turquoise, along with sequins of topaz, the team ignored the color, and instead print-ed the primary puppet as one model in a three-color palette of white, black, and clear resins of varying densities, gradients, and transparencies.
Then, adding a gold Mylar undercoating on the clear sections, UV paint on other areas, and photographing the puppet under three lighting passes – key, fill, and UV – they were able to pull various mattes from the result-ing array of contrasts, tweaking the colors and compositing them in The Foundry’s Nuke. Under the white light key and fill passes, the black would almost disappear, the white would pop, and the gray sections (constituting a blend of white and black) would yield a milky tone.
“The UV pass was like a matte pass out of CG, so we’d get really selective mattes; that was key to getting the luminescence,” says Vickery. “We would get all these fine stroke lines along the edges of the fins, for example, that popped out in UV. Then, we were able to shift the color [in Nuke] and create a matte to make those areas glow, while still keeping the whole body from turning into a big, glowing mess. We also used the UV paint for the eyes, which had to represent the moon.”
To cast the threatening shad-ow the creature trails through the village, the VFX department extracted mattes from the shad-ow passes, in addition to the white light and UV passes, before compositing the layers in Nuke to achieve a consistent look across all 65 of the Moon Beast’s shots.
TEMPEST IN A CG POT
The film’s delicate, multi-layered performances were put to the test in one of the film’s major emotional peaks, in which Kubo, Beetle, and Monkey, clinging to a boat made of origami leaves, must survive a tempest at sea while besieged from above by the Sisters. The roiling waters serve as a poignant counter-point to the sea storm that engulfs Kubo’s mother in the prologue, where a towering valley of waves rise up and col-lapse over her. Both sequences would require water simulation that was not only far beyond anything Laika had done before, but had to match the simplified woodblock aesthetic established by the initial practical rigs.
VFX ARTISTS GENERATED WATER SIMULATION IN HOUDINI AS KUBO ATTEMPTS TO ESCAPE FROM THE UNDERWATER GARDEN OF EYES.
“Stop motion and water sim-ply don’t play well together. It’s a nightmare,” says Knight.
A lot of this action was shot in-camera on the stages, but given the action and interactivity of the water with the boat, a digital solution was also needed, one that reflected the stylized world of Kubo with a nod to the natural world. In effect, the water needed the style of a moving woodblock print, yet it had to behave like the water in nature.
Helming the challenge was Effects Lead David Horsley, formerly of Rhythm & Hues. Working with Emerson, Horsley developed the fluid simulation in Side Effects’ Houdini, blending it with mesh geometry and RenderMan displacement shaders that captured both the whirling and scoop patterning sought for the waves. Effects artists also used Houdini and volumetric shaders for the ominous wall clouds and thunderheads that roll toward the boat, laying them into plates using The Foundry’s Katana and Nuke.
Houdini also powered the effects for the sea spray and the water flooding the deck. For the driving rain, compositor Timur Khodzhaev developed a 2.5D system that incorporated Houdini particles into Nuke.
THE MOON BEAST IS A COMPLEX, MULTI-LAYERED CHARACTER.
Laika divided the fight sequence aboard the boat into two sections, above and below, separating Monkey’s battle with the Sisters on the deck, and Beetle’s attempt to rescue Kubo underwater in the Garden of Eyes. From their pipes, the Sisters blow long, black tentacles of smoke that chase after and seize Kubo, spinning him around like a ragdoll. Laika wanted the look of these Smoke Demons to inform and echo the driving snow of the blizzard in the film, particularly gusts of the denser ground snow. VFX artists generated both the snow and smoke in Houdini using particle simulations driven by force vectors, while animators added significant keyframe animation for the Smoke Demons, as well.
EXTENDING SETS AND CROWDS
Almost every stop-motion set in the film is greenscreened and paired with a CG set extension, lending an epic scale to the village and Kubo’s promontory home, for example. But one of the most important extensions furnishes the Hall of Bones. In this sequence, Kubo plunges from the snowy Far Lands into a bejeweled subterranean hall guarded by a 16-foot skeleton monster. The stage set was 360 square feet, with a very short wall encrusted with 380 12x12-inch jade-colored resin tiles encompassing two-thirds of the set. The CG set elevated the wall to an imposing 22 feet, employing a RenderMan shader for the jade tiles with subsurface scattering.
“We ended up building just one wall and rotating it around, using shader variations to add variety for each tile,” says Wachtman. “Using the one wall, we set it all up in Katana, and used the hierarchy copy, which lets you make another scene graph of the same wall and use attributes to drive shader parameters.”
A pivotal moment of the film sees re-animated ancestors rising from the lanterns in bodies of silvery moonlight. To create the apparitions, the VFX department modeled the ancestors in Maya based on a plastic puppet that had been lit from within, like a lantern.
“We built digital characters to do the same thing,” says Wachtman. “The first thing we did was write all our shaders using [Pixar’s] Slim and the RSL-based system we used for the film. We wrote our own little subsurface scattering that would deal with the light from the interior and refraction.” Using Katana, the shader was hooked up to the asset.
In Katana, artists rigged three little geometry lights in-side the head, chest, and base of each character’s kimono, all of which shed the light that illuminates the scene. On closer inspection of the ancestors’ transformation from lantern to spirit, audiences will see, graft-ed subtly into the transition, Saito’s woodcut textures.
This scene is one of the few to feature digital characters. In fact, even the hyperkinetic origami animations were created by stop-motion animators. Among the only CG origami in the film were a flock of birds that join a songbird in flight above Kubo as he treks through the blizzard, all of which were modeled and keyframed in Maya based on stage-animated origami overseen by Character Supervisor Brad Schiff.
HEART OF RESIN
Indeed, far from being luddites and purists fossilized in a stop-motion world, Laika wants to embrace every tool at its disposal, from photorealistic CG to squash-and-stretch. Kubo and the Two Strings is easily its most ambitious film, not only in the breadth of its technical and artistic reach, but also in the depth of its themes and emotions.
But the bulk of its dramatic accomplishments were powered by innovations in rapid prototyping, innovations that McLean hopes will continue, especially in the area of perfect-ing the fidelity between Maya model and printed resin. “When you look at Monkey and Beetle and how they perform, especially Monkey in the cave, there’s so much tenderness and subtlety in the performances that gives me a lot of confidence that the polyjet technology is the way we’re going to get the most out of these characters.”
Martin McEachern (firstname.lastname@example.org) is an award-winning writer and contributing editor for CGW.