Computer Graphics World

March 2009 22 n n n n CG I•Stereoscopy to raise the bar with simulated clothing," Bielenberg says. "In the past, we were se- lective about how much we simulated and how much we rigged and animated proce- durally. is time, we pushed pretty much all the clothing through the simulation pipeline, even the crowd characters." Light at the End of the Tunnel Of all the groups on the pipeline, the light- ers and CG supervisors probably felt the greatest impact from working in stereo 3D. "ere were twice the number of frames to render, and there was zero tolerance for anything broken in the rendering," Bielen- berg says. "A shadow that worked in the left eye might not work in the right. An incorrect comp'ing order that might have worked in 2D didn't work in 3D. e at- tention to detail hit the lighters and CG supervisors the most, and they had double the amount of work." To help at the very end of the process, the studio used Autodesk's Lustre for digital color correction. "We corrected the color in mono in Lustre, then copied to the other eye, looked at it in stereo, and then did a pass to brighten and warm the shots," Bielenberg says. "e [stereo 3D] eyeglasses add a green tint that darkens the image." In addition to darkening images, a sec- ond aftereffect of stereo 3D is ghosting, an outline that sometimes appears around objects and characters. is happens most often when a bright object lies over a dark background. To fix ghosting problems, the studio devised proprietary contrast- reduction software. "One of our PhDs wrote software that evaluates the dif- ference between the two im- ages," Bielenberg says. "We can dial in the amount of contrast reduction we want. If that doesn't work, we go back to Lustre and reduce contrast or shift lighting. When a planet was ghosting, we put a glow around it. We'll use whatever tools we can." During a San Francisco prescreening for Monsters vs Aliens, Katzenberg said, "is is not my father's 3D. Until now, people made films in 2D and converted them into 3D. at's analogous to shooting in black and white and colorizing. When you au- thor in 3D, you start to enter a new, cre- ative world. Because filmmakers have to think about dimension in every shot, the film is more cinematic. But, it's as if we'd been speaking English and woke up and had to speak Russian." Fortunately, the inventive minds on the production crew were more than up to the challenge for the comedy/action-adven- ture Monsters vs Aliens, the first Dream- Works animated feature authored in the new language. "Jeffrey is out there touting the impor- tance of 3D," Bielenberg says. "We had to make sure the movie had the right stereo impact, that it didn't feel deliberate, and that it was really story-driven." And that, you can be sure, was no joke. n Barbara Robertson is an award-winning writer and a contributing editor for Computer Graphics World. She can be reached at BarbaraRR@comcast.net. Reflections such as those in Dr. Cockroach's eyes (above) caused the studio to create new tools to keep them from shimmering in stereo 3D. At left, the diabolical Gallaxhar embodies all the best in alien design from 1950s monster movies.

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