Issue link: https://digital.copcomm.com/i/119349
VFX•Stereo 3D unique trees modeled, textured, and rigged. "We explored using L-systems and more procedural or dedicated software for the trees, but our modelers and texture painters are very particular about the spans and how they want the UVs laid out," De Jesus says. "It proved to be as much work to change an out-of-the-box tree model as to do one from scratch. Most of our trees were geometry, but for the distant ones, we used textures on flat cards. We kept our renders as efficient as we possibly could." Trees not on flat cards had animation cycles that could be scaled up or down in intensity or speed to help bring the landscape alive. "Depending on the shot, the lighting team could adjust the movement with a slider," De Jesus says. Why the lighting team? "There's a simple fact that any director can comment on certain details only when a shot is close to completion," De Jesus says. "The director might have reviewed a shot 10 or 20 times for animation and have the character performance he wants. But only after lighting and compositing can he consider the whole balance of the frame. Something on the right might distract from a character in frame left." Having the sets lessened the amount of building the Imageworks crew needed to do, but it also made their work harder. "When you have an all-CG shot, it's a really well-understood pipeline these days," Stokdyk says. "You track the actors on bluescreen, track the camera, rotomate to cast shadows. But when you have set extensions, you have to make sure you match-move 100 percent in every part of the frame. You have to figure out where to split the lines and blend the two, especially in [stereo] 3D. If the lighting in part of the set is too hot or out of the sweet spot of lighting, if there's an errant shadow, you have to replace that part of the set. If something accidentally covers the set, you have to remove it. The more you build of a set, the more challenges there are. You trade the beauty of getting something in camera with the technical challenges in post." Flighty Bubbles During one sequence, Oz, the good witch Glinda (Michelle Williams), China Girl, and Finley travel inside enormous bubbles across a landscape. "The bubble voyage begins at dawn," says De Jesus. "They are running from the bad witch, jump off a precipice into the clouds, and when they emerge, they are in the bubbles. They travel on bubbles to her castle, going around, through, above, and below CG clouds." With clouds designed to mimic the landscape below, the crew needed to art-direct the volumes. "We worked out a way to turn any geometric model into a cloud volume," De Jesus says. "The layout team could place the shape and it would turn into a full-on volumetric." The bubbles were spheres deformed by the characters inside when they pushed against the surface with their hands and feet. "Glinda is elegant and poised, so her bubble has that character," De Jesus says. "Oz stumbles and bounces around inside his bubble." De Jesus considers these scenes with characters inside bubbles to be one of the technical achievements on the film. For reference, the crew took stills and videos of giant soap bubbles several feet across in various lighting conditions. "On past shows, we used our volume renderer SVEA and we had to do a lot of cheats. Sometimes effects TDs would light the volumes and the compositors tried to balance the passes to create a look. But about two or three years ago, we incorporated SVEA into Arnold, our global illumination renderer, and that did away with holdouts and lighting issues. It means, for example, if we have smoke that is, from elements inserted into the atmosphere. "Every scene has an atmospheric theme," Stokdyk says. "In Kansas, we had straw and dust blowing through the foreground, which gave us texture and allowed us to art-direct through the [stereo] depth. And, throughout the movie, we have snow, clouds, dandelion puffs, and sparks. We had the 3D photography and the concept artwork, but there are still a lot of art-direction decisions we can make in visual effects. Where to put trees to dapple shadows. Where to position a matte painting for the sky and have clouds that complement the foreground. And we made dozens and dozens of depth choices. It was a great creative outlet." China Town Two of the most creative innovations devised by the crew solved the problem of giving James Franco a way to interact on set with his small CG buddies: China Girl and Finley, the monkey. Oz discovers China Girl when he stumbles across her destroyed village. On set, James The bubbles moving across Oz were geometric spheres deformed by the characters inside and then converted into volumes. next to a red wall, the smoke automatically gets the red bounce. All these subtle things take a scene to the next level. It makes it look real and, in some cases, look beautiful." Thus, for Oz, the artists could light the entire environment and render the scene together with the volumetrics. "The shadowing, global illumination, and bounce light all work out of the render," De Jesus says. "Our render servers have 24gb of RAM, so we piled on details until we hit that limit, and then we were done. You can never have enough detail; the complexity is what makes the scenes look real and interesting." Some of that complexity came from effects – Franco crouched down and peered into a small-scale set built by a crew at New Deal. "We had New Deal, which is a miniature company, build the sets for this little world," Stokdyk says. "But we shot it as one-to-one scale. It has giant teapots, which are the homes for China Girl, her family, and her village. Inside the teapots is miniature-scale furniture." On set, Franco could hold a China Girl puppet in his hand, but 99 percent of the time China Girl is CG. Her size, only 18 inches tall, made it difficult to give him useful eyelines and interaction. A tennis ball on a stick or a laser pointer could provide an eyeline, but not the interaction, and she was too short to have March/April 2013 CGW0313-Ozpfin.indd 13 n n n n 13 3/14/13 12:11 PM