The VFX in Clash of the Titans
With little over a week to go before Wrath of the Titans hits the big screen, we take a look at Warner Bros’ 2010 offering, Clash of the Titans, and discover how the stop-motion epic was updated for the CG era
There are several theories of why otherwise sane, intelligent people grow up to become visual effects artists. Some hold that certain humans are genetically predisposed to need less sleep than the rest of the population; others, that the radiation from monitor screens supplies the vitamins lacking in a diet of pizza and Starbucks.
The truth is far simpler: a child’s development can be irrevocably altered by exposure to the work of Ray Harryhausen. And in Warner Bros’ Clash of the Titans, Harryhausen’s children come face to face with their famous father with the release of a modern remake of the legendary animator’s final full-length movie.
Much as the fondly remembered 1981 feature is a reworking of the myth of Perseus, this 2010 release is director Louis Leterrier’s reimagining of the Harryhausen original. While most of the original characters make repeat appearances – Liam Neeson replaces Laurence Olivier as Zeus, while Sam Worthington plays Perseus himself – the plot differs significantly, with Ralph Fiennes on board in the crucial role of Hades: lord of the underworld, and embodiment of the mysterious ‘essence’ from which its creatures are created.
Medusa, created by Framestore, is just one of the CG creatures populating the 2010 Clash of the Titans
More importantly, all the creatures from this particularly rich mythic seam are present and correct: the harpies, the scorpiochs, Medusa, and the gigantic kraken. When the news broke that work on the movie had gone to three of the UK’s leading facilities – Framestore, MPC and Cinesite – the collective cry of joy that rang around Soho could almost be heard from the far side of the Atlantic. “We’re all huge fans,” says Kevin Jenkins, Framestore’s digital environment supervisor. “Star Wars and Harryhausen are the reasons we do this.”
TEAM SIZE: 200
NUMBER OF SHOTS: 450
CREATURES CREATED: Medusa, harpies (start of film), Hades (cape only)
KEY SOFTWARE: Maya, Houdini, ZBrush, mental ray, RenderMan, Vue, Shake, Nuke
STUDIO: Moving Picture Company
TEAM SIZE: Over 100
NUMBER OF SHOTS: 250
CREATURES CREATED: Kraken, Pegasus, harpies (end of film), Calibos (transformation only)
KEY SOFTWARE: Maya, ZBrush, RenderMan, Flowline, Shake, Nuke
TEAM SIZE: 65
NUMBER OF SHOTS: 242
CREATURES CREATED: Scorpiochs
KEY SOFTWARE: Maya, Houdini, Mudbox, RenderMan, Shake, Nuke
When the news broke that work on the movie had gone to three of the UK’s leading facilities – Framestore, MPC and Cinesite – the collective cry of joy that rang around Soho could almost be heard from the far side of the Atlantic
Framestore was responsible for 450 of the film’s VFX shots, including many of the movie’s digital environments, the harpies, and most challenging of all, Medusa.
“She’s more complicated than other characters we’ve tackled,” says Mike Mulholland, Framestore’s CG supervisor. “She’s not just one character: she’s almost three creatures in one. She has a human upper half, a snake’s body, and [her hair is a tangle] of snakes, which is almost like its own character.”
Sculpting from designs provided by concept artist Aaron Sims, Framestore modelling lead Scott Eaton set to work, completing the bulk of the creature in ZBrush. The polygonal mesh and displacement maps were then brought into Maya, where a custom plug-in handled the remaining surface detail procedurally.
Framestore carefully distributed the snakes on Medusa’s head to convince the viewer that her head and neck are capable of bearing their weight
“Physically her snake body is quite big – it’s probably about a metre wide – so we had to [build the scales as geometry] because we couldn’t get away with texture cheats,” says Mulholland. Custom settings enabled the artists to control the density, size and patterning of the scales on separate parts of Medusa’s body.
“The total quickly gets into the hundreds of thousands, so we didn’t want to have to manipulate each one individually: we were dialling in angle, size and spread, then we had some blendshape noise to make [each one] individual,” reveals Mulholland.
A BEAST OF A RIG
Under this system, the final model clocks in just under 150,000 polys: heavy, but manageable. While the texture work was complicated by the dual-layer subsurface scattering used for Medusa’s human skin, which required four separate subsurface maps for each element of the model, the true scale of the work becomes apparent from the rigging statistics: the final deformation rig has over 5,400 joints and over 1,600 controls.
“She goes through two stages in the film,” says Mulholland. “Her beautiful human face, which is based on Natalia Vodianova [a Russian supermodel], and a [more snakelike] version when she’s trying to petrify somebody. As she transforms, her facial features warp, her nose vanishes and her jaw extends. That was another layer of complexity: as well as building this very complicated rig, we had to build the facial performance and have it be able to morph into a different character on demand.”
“I think Medusa is the most complex rig we’ve ever built. Our lead rigger Laurie Brugger was working on it throughout the entire project: for 12 months,” said Mike Mulholland, CG supervisor, Framestore
The change is sufficiently drastic that Framestore could not employ a simple shape-based approach: as well as localised blendshapes, the rig was structured so that joints could shift as Medusa transforms.
The rig automatically triggers and blends between separate texture sets for the human and reptilian skin, with two further sets of expression-based displacement maps generating wrinkles. To avoid a straight linear transformation, the face was broken into nine separate areas, each one of which could be controlled individually by the animators.
“I think it’s the most complex rig we’ve ever built,” says Mulholland. “Our lead rigger Laurie Brugger was working on it for the duration of the project, so she must have been on it for 12 or 13 months.”
Despite the complexity of the rig, Medusa is entirely hand-animated. No performance capture or clever procedural systems were used, either for the creature’s body or the 60 individual writhing snakes that make up her ‘hair’.
When Medusa attacks her snake-like face added a layer of complexity to Framestore’s already ambitious rig
“When we were trying to figure out ways of doing them, [ILM’s work on] Davy Jones [in the Pirates of the Caribbean movies] immediately came to mind,” says animation supervisor Max Solomon. “But you have to weigh up how cost-effective something is. When we wrote a list of all the things her snakes needed to do, an automated system would have been an impossibly big build for just 45 shots.”
In the end, the mass of snakes was replaced with lo-res proxy geometry showing the approximate volume and position of the ‘wig’ while the animation of Medusa’s body was blocked out. Once finalised, the animators turned their attention to the individual snakes, dividing them into three broad groups: small ones on the top of the head, medium-sized ones to the sides, and long snakes hanging down her back.
These groupings not only determined the ‘personalities’ of individual snakes, but where their weight is supported: a task that involved a careful compromise between physical realism and the need to generate an emotional performance. “Even a single snake is very heavy, so she probably had about 50 kilos on her head,” says Solomon. “We were very conscious of making it feel like [the longer ones] were supported by her shoulders, arms and back. It’s only with the shorter snakes that you feel the weight is on her head.”
Aaron Sims’ concept sketch of a harpy. MPC based the harpies’ movements on hyenas, while their “fleshy but threatening” torsos referenced Iggy Pop
THE TITAN OF THE DEEP
Although MPC created both Pegasus and the harpies for the movie’s climactic sequences, its biggest challenge was the creature that Perseus fends off the harpies in order to reach: the fearsome kraken. The studio’s showpiece is a 40-second full-CG shot – broken up in the final edit – in which the 800-foot beast rises from the harbour, the camera panning around its body to reveal its face in close-up.
The model was roughed out in Maya, with a final pass in ZBrush to generate displacement maps; and rigged and animated in Maya, with the help of MPC’s custom toolsets. With the overall form of the creature – which possesses four crablike legs, a coiled tail, four long tentacles at the base of the spine, and a torso, head and arms of more or less human proportions – already extensively refined by Leterrier and Sims, MPC’s input into the design process came primarily during the rigging stage.
MPC created the awesome kraken. The final rigged and cached model weighs in at 880,000 polygons, rising to 7.1 million as hi-res rendertime wrapped geometry, and uses 1,392 separate texture maps comprising 115GB of texture data in all
“From a rigging point of view, one of the biggest hurdles was that the kraken [starts out] curled up into a ball, and he’s completely covered in ribbed breastplates,” says VFX supervisor Gary Brozenich. “We had to figure out a way the animators could animate him [uncurling] with a minimal amount of interpenetration.”
While the carapace created problems for MPC’s technical animation department, with FX lead Nigel Ankers and his team constantly having to check that individual simulations were not crashing into one another, its hard surface actually simplified other aspects of the rig.
“His torso is quite muscular, so there’s not a lot of fat jiggle; and the fact that he had all these platelets stuck to him helped us because a lot of that jiggle would be supported by rigid objects,” says Brozenich. “Ultimately, we ended up with an IK torso and main body with all the jiggle built into the rig. Very little of that is done with tech anim later: most of it is keyable by the animator.”
In contrast, the kraken’s tentacles – the orientation of which had to be reversed from the original concept designs – were rigged using FK to give the animators more precise control over their positioning.
While the completed skeleton contains 420 joints, the scope of the work is perhaps better illustrated by the other statistics of the rig: it employs 435 plate collision nodes, 300 jiggle deformers, 100 dynamic spring nodes and 80 muscles. The rigged and cached model weighs in at 880,000 polys, rising to a mammoth 7.15 million for the hi-res rendertime wrapped geometry.
BREAKING THE WAVES
To make matters worse, the completed kraken had to interact seamlessly with its environment: the water of the harbour. Flowline, Scanline’s specialist fluid simulation system, was used for the work, with MPC assigning 15 TDs to the job.
For the core motion cache, representing the relatively still waters seen in generic shots, MPC used a Flowline Hydro Fluid surface. A separate stormy ocean, with waves 15 to 20 feet high, was used whenever the kraken is actually present in the scene.
“At the centre, wherever we needed the kraken coming out of the water, or the tentacles going in or out, we’d have a separate smaller Hydro Fluid surface, which would then be patched seamlessly into our generic stormy ocean,” says Brozenich. “On top of that, we ran more Flowline simulations for the secondary particles. But everything hands off from the Hydro Fluid surface, so the real key was making sure we got those forms working correctly, and moving at a speed that was believable.”
Cinesite handled detailed design work on the scorpiochs, creating a kit of heads and claw types for film director Louis Leterrier to pick from
DEATH ON EIGHT LEGS
Meanwhile, a few doors down from MPC in Soho, Cinesite was hard at work on the last of Titans’ showpiece creatures: the scorpiochs. These gigantic arachnids come in three forms, ranging from a 15-foot ‘fighter’ to a 65-foot ‘mother’. In the absence of detailed concept art of the heads and claws, the studio was given a free hand with the creature design, creating a ‘kit of parts’ that director Louis Leterrier could pick from.
Cinesite’s involvement began with the pre-viz stage of the project, with the facility establishing an office on the movie’s set at Longcross Studios, where VFX supervisor Simon Stanley-Clamp could liaise with Leterrier. Sculpted in Mudbox, the models weighed in at around 150,000 polys apiece, each with 47 separate 4K texture maps.
“We kind of over-engineered them, [creating] more detail than we thought we’d need,” says Stanley-Clamp. “The challenge was then to get that to work quickly with the pre-viz. We had three different levels of detail: the initial blocking model; [one with] a low-level displacement map that we could do slap comps with; [and the final hi-res].”
A Cinesite scorpioch meets an MPC harpy. Mercifully, the plot demanded little interaction between creatures created at different studios
In addition to the live scorpions that Cinesite brought into the studio, the look development team had one further unusual source of reference for the scorpiochs’ red eyes: one high in antioxidants. “I gave photos of cranberries to the lighters,” reveals Stanley-Clamp. “They have a nice look: the red light reflects around [inside them], but they’re also wet and sparkly.”
The greatest challenge the team faced, however, was to get the creatures to interact convincingly with their desert environment. Although Cinesite shot an extensive library of practical elements, Stanley-Clamp estimates that only 10 per cent of the dust in the final shots is photographic, with the rest being generated in Houdini. This generated a further problem for the team: when a digital creature interacts with a digital environment, what exactly do you render out first?
A scorpioch attacks. Cinesite faced the challenge of creating convincing interaction with the Houdini-generated CG dust
“You have to cache out the animation to generate the dust, but then how do the shadows of the scorpion project back onto that dust?” says Stanley-Clamp. “The dust casts a shadow on the environment, but the shadow of the scorpion cuts a hole [in that]… and then God rays cut holes in the dust. It makes for a convoluted pipeline: rounds and rounds of caching, round and round in circles.”
Tamed by the heroes, the scorpiochs cross the desert. Cinesite created three separate versions of the models, in four different sizes
THE HAND OF THE MASTER
With three different studios working on the creature effects, the remodelled Clash of the Titans could easily have become a mish-mash of different design and animation styles. Stanley-Clamp attributes the cohesion of the finished work to Louis Leterrier’s overall vision – although he says that Leterrier looked less to the Harryhausen original than to other more recent visual effects sources.
“Louis borrowed a lot from his experience on The Incredible Hulk: big powerful, athletic creatures. There’s this monstrous power driving them; the animation is very full-on, with the power and the energy building up over a run of shots.”
Representatives at the other studios are also quick to emphasise that, despite their obvious admiration for Harryhausen, this version of Clash of the Titans is neither a slavish copy of the original nor an attempt to compete with it – “a remake rather than a redo”, in the words of Framestore’s Kevin Jenkins.
“To me, [1963’s] Jason and the Argonauts was the perfect Harryhausen movie. Clash of the Titans was trying to be a 1980s version of that,” he comments. “There are bits I absolutely adore, but it does feel like it might turn into TJ Hooker halfway through.”
Nevertheless, the hand of the master can still be felt. As Jenkins’ colleague Max Solomon comments: “The shadow of Harryhausen lies over all the monster effects movies. I like the idea that [Medusa was entirely animated] with craftsmanship rather than clever technology or software. I think he would have approved of that.”
Click Next to read Framestore’s digital environment supervisor, Kevin Jenkins, discussing the non-creature effects in Clash of the Titans
on Monday, March 21st, 2011 at 4:49 pm under Features, Making of.
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Tags: Cinesite, Clash of the Titans, Framestore, Making of, mpc, VFX movies, Wrath of the Titans