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Step by Step:
Serenity

Sep 1, 2005 12:00 PM, By Ellen Wolff

Virtual Vertigo

When Universal Pictures gave writer/director Joss Whedon the chance to turn his TV “space western” Firefly into the motion picture Serenity, he took advantage of virtual set design in a big way. Two Los Angeles-based effects houses, Zoic and Rhythm & Hues, created CG environments that would convey the scope of Whedon's futuristic tale. One perilous sequence finds the film's hero fighting his enemy atop a gigantic 1,000ft.-deep generator, where one misstep means falling to certain death.

“Give me something scary,” was Whedon's directive, recalls Rhythm & Hues (R&H) Visual Effects Supervisor Bud Myrick, who co-designed this virtual set piece. Myrick recalls, “We definitely play up the vertigo aspect — looking straight down the mouth of the beast. To get the scale of this seemingly bottomless pit was really important. If the character fell, he would get chewed up by spinning teeth inside the generator. If the fall didn't kill him, the teeth would.”

Whedon filmed the actors against greenscreen with fairly dynamic camera moves. After the lead character climbs up the inside of the generator hand over hand, the duel begins. Myrick says, “We had a sweeping shot that starts by looking straight down, and then the camera cranes up to the two guys fighting on the edge of a high platform. We also had some down shots where a metallic case falls off the edge and we watch it get smashed to bits.”

Chains were required during the greenscreen shoot of the lead actor climbing upward, but their presence complicated R&H's subsequent rotoscoping work. “There were light fixtures on the greenscreen set which threw up lens flare that burned through the chains,” says Myrick. “With motion blur, pulling the chains off the greenscreen was a nightmare.” The tasks of rotoscoping and tracking the greenscreen photography were handled at R&H's studio in Mumbai, India. They used the company's proprietary software Icy and were connected to R&H's server in Los Angeles.

Modeling the CG environment was done in Alias Maya and R&H's inhouse modeler And; animation was handled by the inhouse software Voodoo. Multiple levels of grinding gears were required to convey the massive complexity of this CG model. “Since it was supposed to be 300ft. wide, you can imagine the detail that's needed to sell that scale,” says Myrick. “We also built into our design the ring of lights that were at the base of the set piece, and then we put in lens flares to marry the foreground live action with the CG.”

“One fun thing that I got to design was a walkway that telescoped out from the wall,” Myrick continues. “Each step rotated and locked into place. It has a wire mesh surface so you can see through to the depths of the generator. The actor had walked onto a greenscreen bridge which was pretty solid, but the little extended pathway that we animated coming out of the wall was not as stable. So once we got him off the greenscreen bridge and onto our CG bridge, in 2D we actually rotated him and the step he was on to sell that interaction. Each step on the bridge had a little ‘give’ as he stepped on it.”

When the metallic case plummets to the depths, Myrick substituted a ‘deformed’ CG version to extend the fall of the practical case that had been dropped on the greenscreen set. “We extrapolated the movement down for another couple of hundred feet as it got smashed by the gears,” he says. “Some gears were spinning clockwise and others were moving counter-clockwise.” Once Myrick determined the various speeds of the grinding gears, he wrote a simple formula that allowed him to plug in RPMs for different gears. Subtle sparks of light energy were also animated to convey the feeling that electrical power was arcing inside the generator.

The most crucial challenge for any reflective, large-scale CG set is lighting, says Myrick. “It's always what makes or breaks CG.” Using R&H's proprietary renderer Wren, Myrick's team computed layers of occlusion and reflection passes. “In the light interplay on surfaces, especially for interiors, you can really see how light is occluded by surfaces and bounces off of other surfaces,” Myrick says. “We baked in most of the occlusion. Even though the gears were spinning, there was a shadow pass that had to be calculated. For that we used DSMs [deep shadow maps].” The final touches involved adding lighting from the ring of energy that surrounds the generator core, and also shadows cast by the wire mesh CG bridge. “We just took the shadows cast by the greenscreen bridge and punched holes in them,” Myrick says.

During the compositing, which was done with R&H's Icy software, Myrick added a layer of atmosphere and some final 2D paint touches. “We also have our own 16-bit version of GIMP [the open source GNU Image Manipulation Program] called Movie Paint, which we've modified for inhouse use. We have roto tools in GIMP that allowed me to have all my frames loaded into the paint buffer so that I could flip back and forth. When I was animating electrical zaps, I didn't quite ‘onion skin’ them, but almost.”

The final results gave the director the “scare factor” that he wanted, and he readily conveyed his enthusiasm. Myrick says, “Anybody who's as successful as Joss Whedon could easily be jaded, but he isn't. During one of our screenings he turned to us and said, ‘We have the coolest jobs in the world.’”

For creator/director Joss Whedon's views and a detailed look at the making of Serenity, see the October issue of Millimeter.

Credit Roll

Director	Joss Whedon
DP	Jack Green
For Rhythm & Hues: Visual Effects Supervisor/Art Director/Animator	Bud Myrick
Producer	Lisa Goldberg
Production Designer	Nick Pugh
Lead Modeler	Wei Ho
Lighting Lead	Greg Yepes
Compositing Lead	Jonathan Robinson
Tracking Lead	Dominic Eckroat
Effects Animation	Chris Romano
Lighters	Dan Lazarow, Martin Foster
Compositor	Brian Tatosky
India Coordinator	Pat McCormack

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