Computer Graphics World

January 2009 11 CG Character ■ ■ ■ ■ ing," Roble says. "How do you tell what is facial motion and what is the head moving? ere were no hard points, not even the ears. It was a full-blown research project." Roble solved the problem by devis- ing software that searched on a per-frame basis for the parts of the face that didn't move—the forehead, perhaps, or the jaw. "You can watch [the program] highlight the areas that are most static," Roble points out. "You can give the program hints, but, for the most part, we didn't have to. It just worked, which was a big surprise to me. It locked the face down so that all the motion was based only on the facial performance." Once the artists had a stable face, they began extrapolating Pitt's individual mo- tions from the data. It wasn't an automatic process. ey often had to make such deci- sions as, for example, whether Pitt always needed to move his mouth to raise his up- per left eyebrow. And, they needed to add data where the Contour system stopped— the outer rim of his eye, the edges of his January 2009 January 2009 "This was a nonlinear show," says Steve Preeg, character supervisor. "One of the fi rst things that happened was a collaboration between anima- tion, compositing, and lighting. Our animation reviews were done using [Nvidia] Mental Ray renders and the HDRs." To light the head, the art- ists had to match lighting conditions in such dis- parate environments as the interior of an old-folks home, a front lawn in broad daylight, and the deck of a tugboat on a stormy sea. "The director and DP did a meticulous job in these locations, and our job was to be true to that," says lighting supervisor Jonathan Litt. His team worked with the 360-degree HDR photographs taken on the sets, video footage of the small-body actors, and the survey data. "We completely reconstructed the scene," Litt says, "in- cluding all the lighting apparatus, the bounce cards, the scrims, and other diffusers." Then, rather than using illumina- tion in the spherical HDR images to light the CG face direct- ly, they placed the HDR data on the reconstructed lighting elements. Every shot had its own HDR setup. "Even though reconstructing the set is one step more than we usually take, we went for it because the head was often moving and, in some cases, the lighting was subtle," Litt says. "On one hand, we exercised artistic control. On the other, we wanted to start with the realistic falloff in the local environment." The compositing team prepared the HDR images for light- ing by projecting them in Digital Domain's Nuke onto the 3D set geometry and then re-photographing the environ- ment from the position of the head in the scene. "Once we were happy with the overall feeling of the lighting in previs, we exported the 3D Nuke scene into a form [Autodesk's] Maya could read, and put each light in the HDR onto a card," explains compositing supervisor Paul Lambert. "The lighters could tweak the cards and put objects in front of them." The lighting artists would see a primitive version of the real set around Benjamin, with his digital head and rough hair rendered in Maya. "They had everything of signifi cance affecting lighting on the head, including inert objects that blocked or broke up the light," Litt says. "The kind of things that would be held by C-stands are fl oating around the head in the CG version." The most diffi cult sequence for the lighters was the church tent revival sequence. On set, the DP had used hundreds of lightbulbs hanging from cords and two beauty light sources. Director David Fincher had fi lmed the sequence on a windy day. "The whole tent was shaking, and those cords were swinging," Litt says. "We re-created the entire thing. The cords. Every single light source. There was something about the subtlety of the lights when some cords were swinging and others weren't, and the changes in the camera angles. With- out re-creating it, the shots weren't up to snuff." Often, the artists compared the result to lighting on the body actor in the plate, and having footage from all four cam- eras on set helped them understand how light acted within this shot and others. "[The CG Benjamin's] face is a different shape, and his skin is different from the actor's skin, but we became so familiar with the tonality of each actor's skin, it was still useful," Litt says. –Barbara Robertson Light the Match

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