For Gods’ Sake
Issue: Volume: 33 Issue: 4 (April 2010)

For Gods’ Sake

Visual effects studios use CG tools to create mythic heavens and hell for Clash of the Titans

It has been less than 20 years since the original Clash of the Titans stormed the box office to become the 11th highest grossing film of 1981. Legendary special effects artist Ray Harryhausen, who co-produced the film, created the stop-motion magic for that feature.

This year, three visual effects studios based in London wrangled creatures and composed environments to bring Warner Bros. Pictures’ remake of the 1981 film to the screen. Directed by Louis Leterrier, the action-adventure fantasy stars Sam Worthington (Perseus), Ralph Fiennes (Hades), Liam Neeson (Zeus), and a host of CG creatures, including the Medusa, Harpies, witches, Pegasus, Scorpiochs, and the kraken.

Nick Davis was the overall visual effects supervisor. Framestore effects artists, supervised by Tim Webber, managed Medusa’s multiple snakes, buzzed through Harpie sequences, and smoked the Hades effects in 444 shots. Simon Stanley-Clamp supervised a crew at Cinesite who wrestled a stinging, six-minute Scorpioch battle to the ground. The Moving Picture Company, piloted by Gary Brozenich, flew Pegasus, tackled the kraken, and splashed CG water in 220 shots, many of which are in the end battle. In addition, all the studios created environments.

The floor was originally a marble map of the earth, but to give the throne room at Olympus more drama, Framestore put the gods’ feet in the clouds above a photoreal planet below with mountains, forests, and a moving sea.

Framestore: Medusa, Hades, Olympus

“Normally, we do two or three things a creature or an environment and lots of small effects,” says Framestore’s Webber. “But for this film, we did probably 20 quite different effects. The main ones were Medusa; Hades, played by Ralph Fiennes, who turns into smoky stuff; and the environments.”

At first look, Medusa has a massive snake body, but her body slithers into a womanly shape, and her head has snakes for hair. For her face, Framestore used reference photos of the model Natalia Vodianova. “We had to try to make the snake body merge seamlessly into a human body and still feel snake-like,” Webber says. “The 50-foot snake starts changing into a human body around the hips. You see a slight bulge, a hint of stomach muscle, and the scales smooth out. She has metal armor a kind of metal bra with a snake design.”

Other than snakes in her hair, the mermaid-like Medusa looks human from the upper half, but her lower body is a scaly snake, not a fish. Each individually modeled scale moved with procedural animation as her skin moved. “We wrote an in-house plug-in for [Autodesk’s] Maya to manage the scales,” Webber says. “She was quite a technical challenge. She doesn’t have any dialog, but we needed to give her facial expressions based on Vodianova, so we had a full-on facial animation rig.”

Medusa’s head transforms from a snake to a beautiful woman with snaky hair, and back again. Animators at Framestore controlled the timing of the morph and the individual snakes.

When Medusa petrifies people, her head changes from a beautiful woman to a scary snake. “We had two models in 3D, both animatable,” Webber says. “They had to morph one to the other, so the model could change, the textures could change, and the skin surface parameters could change. They didn’t all change at the same time.” Hints of the snaky face remained, for example, when she morphed back to a human. Animators controlled the timing for the morph and for the snakes.

“We considered procedural techniques for the snakes, but ended up doing a lot of hand animation,” Webber says. “They had very individual behavior.”

Hades, too, sometimes looks human and other times a dark essence. He first appears as long streams that flow through a crowd and join together to form a spout of black vapor with fire inside. The spout becomes a tornado that sucks soldiers inside and then spins into Hades in his human—Ralph Fiennes—form wearing a cloak. The cloak’s edges are on fire.

For the dark essence, Framestore effects artists used Maya and Side Effects’ Houdini, plus volumetric rendering. “It worked differently in different shots,” Webber says. “We had thin tendrils, a giant column of smoke, tiny wisps, a big spout like a fountain, so we used Maya fluids, but mostly Houdini. For the spout, we used different types of fluid solves and then ran particles through it.”

Twice during the film, Hades and the Harpies morph into each other. The first time, the Harpies attack soldiers and then fly together into a spinning ball. The spinning ball becomes the dark essence that, as it slows down, turns into Hades’ cape. The cape opens, and we see Ralph Fiennes, who was a bluescreen element. Animators manipulated the black Harpies into the spinning ball; particle simulations turned the ball into smoke.

The second transition starts with Hades. When he flicks his cape forward, the cape breaks apart and each part becomes a Harpy. To make this possible, modelers built the cape with separate panels. Animators moved the parts away from Hades, and then effects artists ran a cloth simulation that responded to the animation. A 2D morph turned the pieces of cape into Harpies.

In addition to the creatures, Framestore also created several environments—the witches’ mountain, set extensions for Medusa that included caverns with boiling lava and a temple on a hillside, the misty landscape around the River Styx, but the most notable and biggest environment is Olympus. “In the opening shots of the movie, we have a massive fly-through of Olympus,” Webber points out. “We come down through a huge dome filled with tiny statues of humans, fly over a map on the floor and out through a corridor, and then up into the clouds. We based one establishing shot of the exterior on a helicopter plate taken from up in the clouds. Another was completely CG the clouds, the waterfalls, the mountain, the plants.”

For environments, Framestore typically creates geometry and projects textures in Maya using procedural-generation techniques for natural landscapes. “We also did matte paintings and used basic projections in [The Foundry’s] Nuke, and built fully CG stuff with textures, lights, shaders, all completely CG,” Webber says. For rendering, the team used Pixar’s Render­Man and, for the fly-through of the interior, Mental Images’ Mental Ray.

Knowing that shots would take place in the interior, Framestore was prepared to build set extensions for the throne room and the corridor leading there. On set, the floor had a marble map of the earth to illustrate the gods’ power over the planet. But later, this didn’t seem otherworldly enough. “We replaced it with something much bigger,” Webber says, “a photoreal earth with a moving sea, mountains, forests, and floating clouds. The gods walked through the atmosphere. They had clouds at their ankles.”

After some concern that audiences might wonder whether the gods would tread on villages as they walked, the artists decided to make the scene less real. “We made it very cloudy to distract people from worrying about those issues,” Webber explains. “The whole place became a glowing atmospheric place with swirling clouds. We enhanced the gods’ costumes as well, to give them magical glows.” The effects artists swirled the clouds with fluid solvers and created the shapes using RenderMan shaders. Compositors placed the gods in the mist using The Foundry’s Nuke.

Of all the work, Webber is especially pleased with how the crew treated Medusa. “She was a completely CG character,” he says, “a fascinating mythical character with human expressions. Not many films have done photoreal human faces in close-ups, and I think she looks incredibly real even though obviously she’s not. We’re proud of that.”

Cinesite: Scorpiochs
The giant CG scorpions come in 15-, 30-, 40-, and 65-foot sizes and battle the warriors for close to six minutes. When tamed, they become methods of transport across the desert, following one another nose-to-tail like elephants, with as many as six people at a time riding atop in a palanquin. 

For reference, the Cinesite crew filmed four different scorpion species at a scorpion farm and brought two large creatures back to the studio for closer study. “The bigger they are, the less venomous,” Stanley-Clamp says. “We watched how they jumped, how fast they could run, how far they could reach. We got them to run around and follow things. We also saw reference online of amazing fights between scorpions and rats.”

Modelers created the cinematic versions in Autodesk’s Mudbox, and riggers worked in Maya. “The scorpions have eight legs, so they aren’t the typical quadruped, but we’ve done spiders before,” Stanley-Clamp says. “The main consideration was the palanquin.” The riggers constrained the creature’s tail so it couldn’t push through the palanquin, and attached reins from the riders inside to the Scorpioch’s mouth and claws.

Leterrier planned to film the battle between the giant stinging creatures and the soldiers in three areas of Teide National Park (Tenerife, the Canary Islands), so set builders arrived a month early to add broken architecture to the natural environment. That gave Stanley-Clamp and a crew the opportunity to survey the set before the shoot. “We went out a week before filming and did a survey and reference photos,” he says. “We had measurements and a Lidar scan taken the weekend before filming, and we did rudimentary photogrammetry. I also did HDRI photography every hour on the hour for that week.”

In addition, Stanley-Clamp took shot-specific HDRI photographs during filming, but because the action took place in daylight and the sky was rarely cloudy, the early work paid off.

As the crew filmed the action, Sam Worthington (Perseus) fought, in close-contact scenes, with a green-suited stuntman on a pogo stick holding a big block. Using in-house software, Cinesite gave the director a real-time overlay of the CG scorpion onto the live-action footage during principal photography.

For the travel montage, Cinesite inserted the palanquin-carrying scorpions into footage shot in the Canary Islands, Ethiopia, and Wales, adding digital doubles for wide shots and to send people flying through the air if flung off the tail of a scorpion.

As the giant beasts trod along, Cinesite kicked up dust and dirt using Houdini. “We rendered the dust as conventional passes and moved it into Shake with as much depth cuing as we could get,” Stanley-Clamp says. Although the studio’s core compositing tool is Apple’s Shake, compositors also used Nuke on some difficult and dynamic shots. For tracking, they used primarily Science D Vision’s 3D-Equalizer.

(At top) Aaron Sims, character designer for the film, developed the Harpies’ design; animators at The Moving Picture Company gave the winged creatures their personalities. (Bottom) For Pegasus, MPC artists put CG wings on a real horse and created a digital double.

Stanley-Clamp credits the crew’s ability to push through their shots so quickly in part to his ability to go on location early. “We had three months,” he says. “We had to hit the ground running, and everything went to the wire. So we definitely reaped the benefits of getting out to location early almost to the point where we’d pay to go out there ourselves. The crew doesn’t like visual effects on set because we slow them down. They don’t want to get out of the way so you can do a survey. So the time invested upfront pays for itself in the long run.”

MPC: Pegasus, Kraken, Argos
Although VFX supervisor Gary Brozenich began working on the film 14 months before release, from the time principal photography ended and production started, the crew had five months to deliver their 220 shots. “We did a number of different things through the film CG water and ocean, everything that was Pegasus-related, the CG Argos environment, the kraken, and the Harpies, so the end sequence was our main work.”

For Pegasus, The Moving Picture Company added CG wings to footage of a horse shot on location. “Whenever he’s running on the ground, we tracked and roto animated the shoulder area to tightly attach the wings,” Brozenich explains. “We had to replace the upper shoulder to seamlessly blend CG skin, hair, and flesh to horsehair and flesh.”

Because the horse could cover hundreds of yards in a short amount of time, MPC used an elaborate marker system and positioned witness cameras along the route. “We captured the horse from these static cameras to track it in 3D space from multiple locations,” says Brozenich. “We also had Lidar scans of set pieces.”

Rather than a horse that magically flew like a bird, Pegasus would build momentum on the ground and glide up in the air. Once in the air, the horse became a digital double, fully CG, performed by animators.

The enormous kraken, on the other hand, was always fully CG. It has crab-like claw legs, a human-like torso, a reptilian head, a long tail that ends in a series of smaller tentacles, and more tentacles growing out of its back. It is armor-plated. When it rises from the water, the part that is above water is 700 feet tall.

“Rigging was quite an effort,” Brozenich says. “We built into the rig a lot of what we would usually do in techanim [technical animation]. The tentacles used an FK solution because that was the cleanest rig for the animators, but they also went through a secondary pass to add wiggle and jiggle.”

The CG kraken smashes into a digital breakwater as digital water streams down 700 feet of its giant body, and then the monster demolishes CG buildings in the city with its thrashing tentacles. MPC’s rigid-body dynamics solver managed the destruction in these all-CG shots, which took months of development.

To help the animators have something that large move through the city of Argos, the team attached a speedometer to the character and the camera. “The trick was to have his perceived speed move relative to the camera move,” Brozenich says. “We tried to make something that could never possibly be real seem real.”

When he rises from the water, particle simulations in Scanline’s Flowline and in Maya stream water from the surface. During one 40-second shot of the creature’s full body coming out of the water, the compositors layered 60 particle-cache renders. When the creature’s tentacles smash into buildings, MPC’s PAPI, a rigid-body dynamics solver, destroyed the structures. Because PAPI works with the studio’s Alice crowd-simulation software, they were even able to throw digital people into the mix. “We used a combination of PAPI, Flowline, Maya, Maya plug-ins, plus shaders for the water,” Brozenich says. “It took months of development. But, this  was the first time we were able to render Flowline through RenderMan, which was a huge advantage. We could use the same HDRIs and reflection maps, and the TDs could run everything through one lighting pipeline.”

The kraken battle takes place in Argos, which was partially a set piece, but largely CG. “We had one long road, a central square, and four smaller roads off that on set,” Brozenich describes. “We also had a set for a lighthouse. The rest of Argos was computer-generated.”

The city is in a canyon surrounded by cliffs, a sort of arena t hat extends to a large harbor—the harbor from which the kraken emerges. The crew based the cliffs on those in Tenerife, but rather than the existing landscape,

the artists carved a digital gorge, used photos of the cliffs as reference, built an ancient city into the cliff sides, and added a horseshoe-shaped inlet.

“We photographed Malta locations to get architectural types and [locales in] Matera, Italy, to see how structures would be derived and built into cliff sides, then presented story­boards to Louis Leterrier and Nick Davis,” Brozenich says. “Once they approved the storyboards, we shot individual buildings for photogrammetry.” The crew shot buildings in Malta, Matera, Edinburgh and Glasgow (Scotland), and Bath and Oxford (England)—any city with neo-classical structures—and then used the textures to create new buildings in Argos.

“This is a new Greek city, so we needed new buildings, not ruins,” Brozenich says. “The neo-classical buildings were in better shape than the old Greek buildings.”

To manage the huge city, the layout team divided it into sections using London’s postal codes to identify areas in particular shots. “When we’re looking from the kraken’s head view, we see a third of the city, so we loaded that portion,” Brozenich says. “We had tens of thousands of pieces of geometry: props, trees—32,000 trees—and God knows how many canopies, market stalls, streets. And then on top of that are the crowds that we drove through Alice.”

MPC has created cities and crowds before, but this time the studio took a different approach. “We always knew we’d have CG shots with CG characters,” Brozenich says, “the kraken, Perseus, Pegasus, crowds, the Harpies. We wanted to make the city like any other asset, so we lit, rendered, and treated it through the same pipeline as the creatures. That added complexity to the way we rendered shots, but it was part of the normal lighting process. So, we didn’t need to have separate teams on the city. Any TD could pick up and light the city just as he or she would light a character.”

Whether or not these shots push the state of the art of visual effects in general, Brozenich feels the film pushed the state of the art at MPC. “We never expected to be in a position to do a 40-second, full-CG city with an 800-foot creature emerging from a CG ocean. So, in terms of the types of shots we are able to handle, it definitely pushed us. And, from a storytelling point of view, it was a great time.”

It’s amazing that these studios created most of the effects in less than six months. If anyone wants a good touchstone for how far digital effects have matured in less than 20 years, comparing this remake of Clash of the Titans to the 1981 version would be a good place to start.