Issue link: https://digital.copcomm.com/i/17873
n n n n Visual Effects Because Franklin and Nolan had worked together on previous films, they could refer- ence visual memories shared over the past six years. And for the tilting building shot, they both remembered the drawbridges over the Chicago River. “Chris [Nolan] didn’t want plastic buildings that moved like taffy,” Frank- lin says. “He wanted a visceral, engineered feeling. In Chicago, the drawbridges lift great sections of road. It looks like the whole end of the street levers up on a giant hinge, so we used that idea. Te streets would hinge up and arc over, but they would pivot, not bend.” To build a Paris street as a full-CG envi- ronment, the team from Dneg worked with a visual effects team from Lidar Services that scanned the four-block area around Place Georges Mulot over a period of three weeks. “Tey had an SUV with a mast that had a Lidar head on it,” Franklin says. “Tey digi- tized the streets down to a quarter-centimeter level of detail and provided us with a high- detail model. Ten the Dneg team did an ex- tensive photo survey of all the buildings.” In addition, because the crew couldn’t get per- mission to helicopter low over the city, to cap- ture a view looking down onto Paris rooftops, they turned to the Internet for images. Te Internet images, the combination of Franklin says. “We built a straightforward ani- mation tool set system to place the people and traffic in the shots.” Paris Light Although sending people walking up vertical streets and tilting buildings might seem to be the trickiest part of the shot, the challenge was in making everything look photoreal. “If you fold a building over on itself, you can’t see the sun anymore,” Franklin says. “So we had to work out a way to light the street to look natural, yet still fit with the live-action pho- tography. Te actors are in broad daylight, lit by the sun. But, we couldn’t have light shining through a building.” Te answer was mystery light sources added artfully. “Te lighting had to be so seamless that you never question it,” Franklin says. “It’s a dream that has to feel real. Tis sequence exemplified the key challenge in all the work: No matter how outlandish the imagery—fold- ing streets or a café blowing up—we had to ground it with convincing, absolute reality.” Te lighting was so complex, in fact, that the crew could not use Spangle, the interac- tive, in-house lighting tool developed at Dneg for Te Dark Knight. Instead, they relied on optimized shaders and raw renderfarm power. a per-face adjacency map in one texture file for each surface. First used for Bolt (see “Back to the Future,” November 2008) and “Glago’s Guest” (see “Short Subjects, Big Ideas–Simple Truths,” February 2009), the technique uses adjacency data to do seamless anisotropic fil- tering of multi-resolution textures across sur- faces, even those with arbitrary topology. Te technique works through RenderMan. “Basically, with this new way to map tex- tures onto 3D geometry, we didn’t have to go through the process of setting up UV co- ordinates,” Franklin says. “We used this more sophisticated projection system to map all the textures in the Paris street scenes. We’ve done photorealistic environments before at Double Negative: Gotham City, Chicago. But this sequence happens in broad daylight, in high- contrast sunlight. We had fantastic, beautiful plates shot by Wally Pfister with 64mm clear, anamorphic cameras. Tere was nowhere to hide. And Chris [Nolan] insisted the digital buildings be equal to photography.” Compositing supervisor Graham Page placed the live-action actors in the digital en- vironment. But, before he did so, the artists re- alized that the movement of the actors looked too mechanical. “He worked out a brilliant way to separate the actors even though we filmed them in the same pass,” Franklin says. “And then, he changed the timing to make the shot feel more organic. It was a tremen- dous piece of compositing.” Te compositors all worked at 4k resolution using the tools that Dneg’s R&D department created for the IMAX version of Te Dark Knight to overcome Shake’s memory limitations (see “Extreme Effects–Dark Inspiration,” August 2006). “I don’t want to play down our technical achievements, but this sequence is a testament to the artistry of the crew,” Franklin says. Visual effects artists scanned, modeled, and texture-mapped a four-block area of Paris so they could pivot digital buildings up and around the live actors. A texture-mapping technique developed at Disney helped the Double Negative artists create the photorealistic digital set. data from the digital scans and the photo- graphic textures made it possible for CG su- pervisors Dan Neal and Philippe LePrince and their teams to create the highly detailed digital models of all the buildings. And more. In the shot, everything not on the horizontal, except the actors, is CG, including the buildings, cars, bicyclists, and pedestrians. CG crowds jostle on the sidewalks. “We photographed all the extras, made little 3D models of them, and drove them with a motion-capture library,” 14 August/September 2010 To render the digital buildings and people, Dneg used Pixar’s RenderMan and an updated shader set. “Philippe [LePrince] developed a new shading and texture-mapping system us- ing the Ptex technique invented at Disney,” Franklin says. Ptex, per-face texture mapping for produc- tion rendering, developed by Brent Burley and Dylan Lacewell at Walt Disney Anima- tion Studios, stores a separate texture per quad face of a subdivision control mesh and If You See My Reflection In the final part of Ariadne’s Paris dream, she and Cobb walk out of the cube and toward the banks of the River Seine. As she approaches a road on the lower level, a bridge springs up out of the ground and builds itself toward her. She then walks onto the bridge. “Te idea sounded brilliant in the script,” Franklin says. “Everyone can imagine it. But building it so that it doesn’t look comical in reality was difficult.” Nolan shot the sequence on Pont de Bir- Hakeim, the same location used by Louis Malle in Frantic and Bernardo Bertolucci for Last Tango in Paris. “We didn’t have the time or flexibility to build a greenscreen on loca- tion,” Franklin says. “Chris [Nolan] and Wally