Computer Graphics World

March 2009 19 CG I•Stereoscopy n n n n model." Helping that along was a new po- lygonal model format developed internally that allowed the technical artists to specify arbitrary attributes at a vertex level. At first, the artists wrote a special shader to transfer normals at render time from the patch surface to the polygonal version of the model, but the result had artifacts that caused "chattering." "We could smooth them out and reduce them, but we couldn't get them to go away," Boylan says. "So, we decided to steal the normals that worked in the patch model and apply them to the polygonal model." To sell the idea of a liquid, lighting used refraction. It turned out, though, that re- fraction and reflections became an interest- ing predicament once viewed in stereo 3D. "You can render specular and reflections correctly, but sometimes when you get them on the screen, given current projec- tion technology, they can read differently in the two eyes and create a shimmer," says Ken Bielenberg, visual effects supervi- sor. "It's physically correct, but it's not pleasing." us, rather than calcu- lating the true reflections and specular for only the two eyes, the CG art- ists also simulated the result from a center camera so they could choose that simula- tion instead for the left and right cameras (eyes). "It has the effect of changing the depth," Bielenberg says of the simulation. "In the extreme, you see a reflection mapped on something, instead of seeing the depth. However, we have a creative knob so we can dial between true and fake reflections. We almost always use true reflection. But BOB has such variation in his shape, as well as lumps and blobs, that the reflec- tions and specular differences were ex- treme between the two eyes. So, we found a happy medium." In the Deep e crew was approximately three months into development when Jeffrey Katzenberg, DreamWorks' CEO, decided that Monsters vs Aliens would be the studio's first film au- thored in stereo 3D from the beginning. "Jeffrey said, 'We'll show you what it en- tails,' " Vernon relays. "And then the studio gave us 300-page books with a lot of math. I became an artist because I don't under- stand this stuff." Phil (Captain 3D) McNally jumped to the rescue. "He took us into the theater and broke it down for us," Vernon says. McNally explained that the more the cam- eras converge, the less the 3D effect, and the less they converge, the more the 3D ef- fect. Using a laser pointer, he showed the directors where objects were in relation to the floating stereo window frame. "He taught us all the tricks of the trade," Vernon notes. "We learned that 3D wasn't just about poking things out of the screen." e directors decided to use the depth to bring the audience into the screen as much as possible. "We started looking at 3D in our layout pass when we had really rough, blocky shapes and forms," Vernon says. "If anything hurt our eyes or overtly popped out, we'd take it out. First, we made the composition and camera nice, and then pushed 3D later on. We constantly looked at each shot, each sequence, and then the entire movie in 3D to make sure we used 3D to its full potential without calling at- tention to itself. We cherry-picked the places where we could poke out from the screen." Even though the directors used 3D with a deft touch, Vernon believes that in many ways this is a perfect film for stereo 3D. For example, stereo 3D helped drama- tize the characters' size—especially that of Susan/Ginormica, the almost 50-foot-tall woman. "We could actually push far back, way into the screen, to get that depth," Vernon explains. (Above) Stereo 3D helped the directors emphasize the size difference between the 49-foot-11- inch-tall Ginormica and the normal-sized General W.R. Monger because they could push her deep into the screen. (Left) Insectosaurus could shoot silk out into the audience.

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