Computer Graphics World

August 2009 21 CG Characters•Stereo n n n n however, produced only 76 results, not all of them useful. "For most people, they're pests, not pets," Saliba says. "ey have tendrils coming off their nose in a star pat- tern that are prehensile, like another set of hands. ey're not cute and cuddly." On set, because the main characters are less than a foot tall, Yeatman brought the cameras down low. "Hoyt and the crew had special lenses and grips that allowed the first-unit camera operator to hand-hold a camera at guinea pig level," Stockdyk says. Once the shots moved into post, the crew would often add a slight zoom, change the framing a touch, and tweak the timing. "In some cases, if we pushed the limits," he adds, "we'd go completely virtual. Almost everything had virtual backup." To capture the lighting setups, the crew used Yeatman's "ChirpiCam." Maury de- scribes it thus: "It's a one-and-a-half-foot cube that has five cameras with fish-eye lenses mounted inside that takes expo- sures every two stops, from eight seconds to an eighth of a second up and down. We put it in the middle of the set each time the lighting changed, and pressed Go. It stitches the images into HDRI maps." Maury says the camera received its ChirpiCam name because it chirps as it captures the HDRI images. By the time the production unit fin- ished shooting, ChirpiCam had provided the postproduction crew with 800 HDRI images in 360 degrees from a guinea pig's point of view. Maury followed the images all the way through the digital interme- diate process at Company3. "It was im- portant for our comps to hold up at the DI house, so we bracketed every image up and down six or seven stops to make sure the CG highlights would look good in all the different formats," Maury explains. "We pushed the images around a lot, es- pecially the stereo images because they are not as bright." By choosing to shoot the film with stan- dard cameras rather than bulky stereo 3D cameras, Yeatman and the cinematogra- phers were free to choose any lens and light- ing, and to shoot at guinea pig's eye view. But, that choice created interesting chal- lenges for the Imageworks stereo 3D crew. "In the 2D version of G-Force, about two-thirds of the film includes visual ef- fects, and the rest of the film is live-ac- tion plates," Engle says. "In G-Force 3D, every shot in the movie is a visual effect. So, the first thing we did was divide up the workload." Stereo Solutions Imageworks gave all the shots without CG effects to In-ree to convert those plates to stereo 3D. "ey cut out elements by pulling keys and by using rotoscoping to isolate and offset them, to produce the per- spective you would see with the other eye," Engle says. For the plates that would include the CG characters, Imageworks needed to take a different approach, but even so, relied on a typical pipeline. "Our crew is organized like most visual effects crews," Engle says of the stereo 3D artists. "We're basically using visual effects processes for everything: Layout takes the matchmoves, adds extra geometry to mim- ic the real world and make sure it's logical, Director Hoyt Yeatman put the cameras low to help the audience relate more directly with the star-nosed mole (at left) and the guinea pigs, including the one above. Similarly, the stereoscopic 3D team tuned its cameras to the stereo depth that a guinea pig might see.

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