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Step by Step: Beowulf

Nov 14, 2007 3:50 PM, By Ellen Wolff

There’s a moment near the finale of Paramount Pictures’ Beowulf that reflects the wide-ranging techniques needed to pull off Director Robert Zemeckis' massive digital experiment—from motion capture to keyframe character animation and environmental simulation. It’s the moment when King Beowulf and his faithful sidekick confront a huge dragon bursting from its cave, breathing a column of fire. Snow swirls around the scene and the rock wall of the cave blows outward with the dragon’s force. And since this scene was designed to take full advantage of a stereoscopic presentation, the fireball erupting from the dragon blasts right past the camera’s lens.

“We called this the bark- at-the-moon shot,” says Jerome Chen, senior visual effects supervisor at Sony Pictures Imageworks, which handled the digital assignment for Zemeckis’ production company, ImageMovers. The Oscar-winning Zemeckis was intent upon pushing Imageworks’ performance-capture techniques beyond what they had accomplished with The Polar Express and Monster House. “I feel like we started over with Beowulf in our education on how to do these kinds of movies, because the level of realism that Zemeckis wanted made it much harder,” Chen says.

A major advance came with the capture process itself, which was done in a 25’x25’ space—more than twice the size used previously. This enabled Imageworks to capture the motion of the horse ridden by a character in this scene. Actor Brendan Gleason rode a horse that reared up, and both were mo-capped together, Chen says. “We captured Brendan’s facial performance at the same time, because we liked to keep the bodies and faces together,” Chen says. To capture the subtleties of the actors’ eye movements, Imageworks also used a tracking technology called EOG (Electro-OculoGraphy) in which data was captured via electrodes placed around the actors’ eyes and transmitted to mini pocket computers.

“Tracking was the first step in decoding what was filmed by the motion-capture camera,” Chen says. “It’s just a cloud of dots in three dimensions. The tracking person figured out where each of those dots belonged—on the horse, on the people, or on their faces. Since Polar Express, we’ve gotten better at sorting through the dots and finding the nuggets that we’d need to apply to a character. The tracking was done with some in-house tools and [Autodesk] Motion Builder, because of its motion editing tools and real time capabilities.”

“After that, we did the camera layout part,” Chen says. “In a big capture volume you don’t really see the point of view of what the camera will see until Bob Zemeckis does the camera layout pass. Bob came up with a camera view that began with a close-up on Beowulf, then moved to Brendan and back to the dragon. The camera does move around quite a bit in the shot to show the foreground move relative to the background,” Chen says.

The next step required something that a human-wearing mo-cap markers couldn’t do—which was to create the towering, winged dragon. Animation supervisor Kenn McDonald oversaw that, working from a cyberscan of a maquette, and using Autodesk Maya to keyframe the movements of the beast. The human character animation and the simulation of cloth and hair on the actors was also done in Maya, but the grooming of their hair and the building of their costumes was done with proprietary tools. “We made huge advances in cloth and hair tools to deal with extra level of realism on this show,” Chen says. The characters, as well the cave wall and trees in the scene, were rendered in Pixar’s Renderman.

The environmental simulations required for this shot were especially complex, Chen says. “The rock wall had to be exploded outward and then disintegrated in a cloud of dust,” he says. While Maya’s rigid body solver was used for the rocks that are propelled from the cave as the dragon bursts forth, the dust cloud was a particle sim done in Side Effects Houdini and rendered in Splat, Imageworks in-house renderer. Making these software packages work efficiently together required some proprietary “glue” tools.

The ability to move back and forth between Maya and Houdini was crucial for simulating the fire within this shot. “We adapted the fire pipeline created for Ghost Rider, which was developed by Patrick Witting and Vince Serritella,” Chen says. “The system works on the idea of how much fuel there is feeding the fire—it’s very customizable in terms of its motion. It can do realistic fire, and we can also art direct it. We used Maya’s fluid solver to create the motion of the fire, and then we brought it back to Houdini to light it.”

“There’s a concept of a simulation box, which is the parameters that you simulate in. To do a box the size of the whole cliff wall and simulate fire within that would have been computationally prohibitive,” Chen says. “So we put a box around each one of these little pieces of fire. We layered the little boxes together and basically told the fire to simulate within them.”

Rendering was then completed using Imageworks’ volumetric renderer Svea. Although this scene had a big stereo effect of a fireball moving past the camera, the extra rendering wasn’t too onerous. “We decided that the view for the 2D release of the movie would be our left eye,” Chen says. “Though it was still render-intensive, we just had to create one more eye.” Challenges like Beowulf don’t happen often on what Chen calls “the journey of CG.” But now, he admits, “I crave them!”

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Credit Roll

Director: Robert Zemeckis

DP: Robert Presley

Dragon Design: Doug Chiang

Visual Effects Supervisor: Jerome Chen

Digital Effects Supervisor: Sean Philips

Animation Supervisor: Kenn McDonald

CG Supervisor: Theo Bialek

FX Supervisor: Theo Vandernoot

Cloth and Hair Supervisor: Sho Igarashi

Animation Lead: Stephen Enticott

FX Lead: Vincent Serritella

Hair: Zack Weiler

Cloth: Jeff Edwards

Color and Lighting: Cara Paul

© 2008 Penton Media, Inc.