“I really hate the creature film convention that says you have to wait until the end to see the monster,” said Bong Joon-ho, director of The Host, addressing the horror’s early revelation in the film. “One hour and all you’ve seen is just the tip of the creature’s tail. I really wanted to break that convention, so I show the entire creature early in the film.”

The monster, in essence a mutated fish, was designed by Korean artists Chin Wei Chen (who did the preliminary concept work) and Jang Hee-chul (who refined the conceptual design, and created the textures) — in strict collaboration with the director. As part of the film’s environmental and political commentary, Joon-ho was first inspired by a real-life occurrence of a mutant fish with a curved spine, found nowhere else than the Han River. “The monster’s appearance is not based on a pre-existing model,” the director told Korean Film, “The starting idea was taken again from a true story. I read in the newspapers about a deformed fish with an S-shaped spine caught in the Han River. The monster design came mainly from this strange discovery.”

Joon-ho’s basic guidelines to the designers included the concept that the creature should be based on reality — having to resemble a mutated animal — and that it should be able to perform complex, acrobat-like stunts. “I gave [Wei Chen] the idea of the basic size,” Joon-ho said in an interview with TIFF Cinematical, “that he shouldn’t be as big as a building — so he could hide behind a truck. And rather than being a fantasy-type creature, he should look like he belongs in the real world. Like an actual mutated creature. It should look somewhat like a fish, since it comes from the river. It should also run fast on the land, do back-flips, move from front paws to back paws, and show some complicated acrobatic movements. Those are the concepts I wanted the designers to start with.” The creature was established as being 45 feet in length.

Wei Chen and Hee-chul went to extreme lengths to convey Joon-ho’s vision, conceiving a wide array of concept designs ranging from serpentine iterations, to more fish-like configurations. As selected, the final design resembles a grotesquely-mutated catfish or carp, with a multi-pieced mouth, potent front limbs to propel itself on land, and prominent elements of asymmetry — such as a diseased, wart-ridden eye, and an additional arm on its right side. The colour scheme was again based on fishes — such as tunas and carps. CG Supervisor Shadi Almassizadeh compared it to “a carp mixed with a T.rex.”

Once the final design was established, it was conveyed into a small scale maquette by Weta Workshop, which served as the base of the full-scale animatronic creature head, built by John Cox’s Creature Shop, and the digital Monster effects by The Orphanage.

Joon-ho was initially skeptical about using practical creatures, intent on portraying the monster as a wholly digital character; artists of the digital effects team themselves convinced him otherwise. Construction of the full-scale animatronic was assigned to John Cox’s Creature Shop; Cox and his team sculpted the full-scale head in its various components, moulded it, painted it, and built the inner mechanical armature. The skin was moulded in foam latex; the eyes were built in coloured glass and plastic; and the teeth were moulded in dental acrylic and resin.

The animatronic featured cable-controlled as well as radio-controlled mechanisms. It was mounted on a rig and could perform a wide range of movements: the jaws, mandibles, tongue, gills, and eyes all featured independent mechanisms. Once on set, the animatronic was given the final touches with KY Jelly and artificial blood. The animatronic is seldom seen in the film: it was used in close-ups, insert shots of the monster swallowing victims, and the visceral scene where Gang-du extracts Hyun-seo and Se-joo from the giant maw of the monster; the interior of the maw was specifically designed with a structure that could allow the actors to enter the esophagus and be extracted from it.

For most of the sequences it appears in, the creature was brought to the screen by The Orphanage as a digital effect. At the time of production of The Host, the company had not yet created a creature rig and system, and had to establish one from the ground up. “While The Orphanage had done a few CG characters in the past,” said VFX Supervisor Kevin Rafferty to Animation World Network, “there wasn’t really an established creature pipeline and workflow. We used The Host as a vehicle to leverage our existing Brazil-based pipeline and workflow into one that was more robust. The largest addition to our workflow was establishing a creature department and its supporting software, and [implementing] that into our existing pipeline.”

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With a low budget and a short production time, careful planning was essential to the creation of the monster. “I really wanted to have well-made special effects,” Joon-ho said, “but the budget was such that it would only allow me the ‘kitschy’ effects. So there was a lot of pre-planning on how we could do excellent effects with a limited budget.” To save time, the visual effects artists were split into two teams: one team, led by Stephane Cros, developed a motion rig in Maya for the articulation of the body and complex head of the creature. The other, led by Brook Kievit and Sasha Pouchkarev, built the actual digital model of the monster — with Maya and Silo; zBrush was also used to add further texturing and detail. This approach proved crucial to deliver early creature animation tests submitted to the director for approval. “By dividing up the team, we were able to get [temporary] rigs to the animation team much earlier to begin walk cycle testing,” Creature supervisor Corey Rosen said. “How the creature moved helped the director envision how the model should look. So, crucial questions got answered in the proxy model stage, meaning less time would be wasted later revising a further developed high resolution model.”

A Polygon Box Modeling technique was employed to allow the proper amount of detail as well as extreme deformation — essential to the actions the character had to perform. The monster’s complex mouth apparatus required a live cluster-based facial animation system. “She has a five-way maw,” said Rafferty. “The top maw is an almost Giger-esque type of thing. It was a rigging challenge to make it open and close believably.” For the general body movements, a multiple rig system was deployed and adapted to the requirements of specific sequences. “A key strategy was the use of a Multi-Skeleton Rigging System,” Rosen said. “It allowed us the flexibility to develop new replacement — or customized-for-shot — rigs on an as needed basis, and the interfaces necessary for plugging them into the actively flowing creature pipeline. The Host’s rig, quite simply, would have been too heavy, slow, and cumbersome for any artist’s machine to handle if it was monolithic. By developing and implementing a Multi-Rig System, we were able to add layers of complexity throughout the development of a shot.”

A muscle rigging system called oMuscle was developed specifically for the project, as well as an array of customized cluster muscle, skin and lip articulation tools to simulate fast and efficient muscle dynamics. Thirteen animators created the mutant carp’s monstrous performance. Texture maps were elaborated in Photoshop, and implemented in 3DS Max. “We sent Jang Hee-chul, the creature designer, a file that was UV’d and he created the first iteration of textures by painting color diffuse maps in Photoshop,” Almassizadeh said. “Then, we had our texture map technical director create the other maps.” The maps were composited under the supervision of compositing supervisors Steve Jaworski and Alex Prichard.

Animating the bizarre monster was a difficult process, again because of its unique anatomy. Both earlier examples of movie creatures as well as footage of various animals was used as reference. Rafferty said: “We gathered information from both real life and past films. We looked at the T.rex in the Jurassic Park movies for weight and mass reference. We looked at Draco from Dragonheart to see how rain looked on a large reptilian skin. And we looked at Predator and Blade 2 to see how other films dealt with [animating] a multi-faceted mouth, or maw.”

Animation supervisor Webster Colcord wanted to ensure that the creature would perform not only naturalistic but also physically believable movements — with the correct sense of mass and weight. Colcord’s first assignment was developing a running cycle, which he based on legless people walking on their hands, as well as sea lions for the physical reaction of fat layers beneath the skin. “I looked at the famous legless performer, Johnny Eck, in the movie Freaks, as well other legless people,” Colcord explained. “When you look at those real-life examples, it’s all about the transfer of gravity from one shoulder to another. The difference was that our creature has a tremendously long and heavy tail. So, our reasoning was that this tail would only lift off the ground when she reached full run speed. The nearest reference we could find for the weight and shape of her body were very large sea lions. So, we kept that in mind while animating weight passes bounce, jiggle in the creatures belly and on down through the tail.”

Since it is a mutated fish, the monster is initially clumsy on land — only to become more accustomed to it as the film progresses. Footage of crocodiles, snakes, amphibians and fishes was also used as reference. “Luckily, one of our animators, Bruce Dahl, has a tremendous library of reference footage that we pulled from,” Colcord recalled. “We tried to make the Host a little clumsy on land in the first few appearances — but as the movie progresses, the creature becomes more comfortable on land. For the swimming scenes, we modeled the motion after a crocodile — the arms were not involved in propulsion. When she uses her tail to grab things or swing, we looked at some incredible footage of a huge snake climbing a tree. In some of those tail-grabbing shots, we had to use a tail-only rig wherein the tail geometry would deform along a spline, but most of the time, we tried to do all of the required actions of the tail with one rig.”

The creature’s various distorted fins and “dangly bits,” as described by the animation team, were animated manually, due to the fact that an automatic simulation system could not be developed in time. Finishing touches included layers of jiggling muscles and fat in the arms and abdomen of the creature.

Interaction of the creature with the environment was implemented with complex particle simulations for water, dirt, and fire. In one scene, where the creature drops on a truck, two weights were dropped on the vehicle — only to be replaced with the digital character in post-production. Another particularly complex sequence involved the mutant lowering a character with its tail, and regurgitating another one. “We had made the conscious decision not to use blue screen or motion control,” Rafferty said. “This would give director Bong and cinematographer Kim much more freedom for camera placement and movement. The shot posed many challenges for the artists. First of all, plate restoration was a big challenge. There were so many rigs and cables in the plate (to support the actors) We did shoot a clean plate, but it was not accurate to the action plates motion. The roto/paint crew utilized these clean plates where they could, but often worked with the MatchMove artist, and projected a single frame (frame-averaged to remove grain) into the CG environment. That element would then be used for rig removal and paint, adding back the grain once finished. Before the artist animated the creature, he first needed to use proxy characters and match the animation to the live-action actors motion. His next challenge was then to create a forceful, believable performance of the creature that obeyed the limitations of the matched animation of the actors. Once the creature was lit and we had our first composites coming through, we quickly saw another challenge. The tail was now releasing around the actor, but the clothing wasn’t pinching and bunching up. Our compositor very carefully mesh-warped and morphed his way through this challenge. This was the last shot finaled on the show!”

In the film’s third act, the creature is severely damaged by Agent Yellow, and is then set on fire by the Park family. The visual effects team devised two progressive damaged skin textures. Rafferty related: “we had three textures for her: her normal dark green skin that has been untouched by human hand; a blistered look when she gets doused with Agent Yellow; and, once she’s set on fire, we charred her underlying green and blistered textures.” The team burned some dead fishes to gain reference. “We even went to the fish market and bought a trout and a bass,” Rafferty said. “We brought them back the studio, poured lighter fluid on them and set them on fire! We filmed this for reference on how a fish skin would look if it was set on fire.” Originally, the creature was to be wounded even more by Gang-du, who ripped one of its eyes off and slashed across its skin in multiple areas; those scenes were filmed with the animatronic, but were ultimately cut.

Rosen concluded on the experience on The Host: “for The Orphanage, the project definitely marked the beginning of a new era. It’s amazing to see what The Host has helped our studio become, technically, and creatively.” Joon-ho was also extremely satisfied with how the creature was brought to life. “The similarities between these artists are that they’re young, and advance-minded, which allowed us to get very good effects on a limited budget. The Orphanage, in particular, is a very “chipper” collection of artists. Very talented and open-minded, not afraid to show the monster in broad daylight.”