Computer Graphics World

March 2009 34 HD cameras as he performed FACS-based phonemes and emotional expressions. Modelers and riggers used this data to cre- ate and control face shapes and poses. "e motion-capture team would ana- lyze the video footage, tracking the dots on Billy's face in 2D with proprietary software, run an analysis, and get back a 'solve,' and that drove the FACS poses," Travers explains. "As the dots moved, they triggered a certain percentage of each pose, and that fed into the control system. e main thing the facial-tracking system gave us was a good sense of timing." us, although the system didn't match the shape of Crudup's expressions exactly, the timing helped an animation team led by Kenn McDonald re-create performanc- es more quickly. "When you're matching an individual performance, it's the number of frames, not the number of shots, that's important," Travers says. "We had dialog shots that were 500 to 600 frames long." To reproduce Crudup's expressions, the animators painstakingly worked on a split screen, with video footage on one side and the CG model on the other. "In my opin- ion, the only way to make human anima- tion look right is to give talented animators time to do their work," Travers says. "We tried to supply the animators with as much weaponry as we could to get it done." Riggers provided some of that weaponry in the form of facial controls designed for subtle touches and a stoic demeanor—a slight nostril flare, an eye twitch, crow's feet, facial tics. "ere's a shot in the ex- panded DVD release in which Malin tells Dr. Manhattan she slept with another guy," Travers says, referring to actress Malin Ak- erman who plays Silk Spectre II. "Doc's head turns a little and you see a little bit of muscle flex on the back of his jaw because that's what Billy did." Inside Swirl Although Dr. Manhattan has a human form and facial features, he's made of galactic material. Internally, he has a fi- brous structure, but no bones. Gases swirl throughout his translucent body, in his chest, and in his appendages, becoming wilder when he attacks an opponent. To achieve that look, the Imageworks crew borrowed techniques and technology from a system originally developed to art-direct the fire in Ghost Rider (see "Blazing Effects," Feb- ruary 2007). For Dr. Manhattan, they cre- ated layers of dense particles in Side Effects' Houdini that, in turn, derived a volume. Imageworks' proprietary volume renderer, SVEA, rendered the flowing particles. e crew also spent time creating de- tailed skin textures by starting with photo- graphs of Crudup, and then tinting the painted textures blue. "He looks like a blue man, but not a painted blue man," Travers says. "I've learned that when you do texture capture, you have lighting built in. When you add lighting after you apply the tex- ture to the model, you've double lit it. So we cranked the contrast in the texture, the bump, the sheen, everything, and the detail looked right. You could read the texture." To keep the CG character's skin from looking too smooth, they covered his body with peach fuzz, little hairs that caught the light. On his face, they added eyebrows, lashes, and tear ducts. And, as is common now, the lighting artists used subsurface scattering to make the skin look fleshy, but they reversed the typical use of ambient oc- clusion. Usually, ambient occlusion creates soft shadows in areas light can't reach—like a character's armpits. But because the skin of this character emits light, his armpits were doubly lit. Am I Blue? In addition to Dr. Manhattan's well-lit in- ternal structure, the character also has an external glow. Rather than cheating the glow using a 2D system, the crew built a 3D volume that surrounded the CG char- acter as he walked around. "We parented the glow to his body," Travers says. "We could dial in how much glow he had. If he put his hand on his chest, we doubled it up." e color of the glow ranged from cyan close to the character's body, to indigo far- ther away. Similarly, Dr. Manhattan's skin Tiny hairs covering Dr. Manhattan's body catch the light and help make his impossibly blue skin seem to have possibly human origins. The glow surrounding the blue superhero is a 3D volume parented to his computer-generated body. n n n n Character Creation

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