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PREVIS www.postmagazine.com 36 POST MARCH 2016 characters and props, animating the action and bringing in motion capture perfor- mances. We then worked with the director and his production crew to support devel- opment of shots through virtual camera." Between production and post, The Third Floor created postvis for around 250 shots. "As live plates became avail- able, postvis artists composited temp backgrounds and key elements to replace greenscreens from the principal shoot," Hull continues. "These working versions were used in further developing the shots in virtual camera sessions, visual effects and editing." Prior to the theatrical release, a team from The Third Floor also collaborated on the film's teaser trailer, with previs and vir- tual camera work for a dramatic pull-out from Philippe Petit (portrayed by actor Joseph Gordon-Levitt) on the wire to the clouds above the World Trade Center. According to Hull, previs was essential to the filmmaking process on the film, and once it was approved, it was able to support much of the virtual camera work required to pull off some of the daring shots that placed Petit high above the ground. "This is where the magic happens," he says. "Where the essence of a shot can be explored using representative visuals of the scene with the freedom to move and position the camera. Because the virtual camera can be captured and played back live, you can adjust positions of props and timing of performances without bogging down any creative thought in the moment." Key scenes where previs played an enormous role were during the walks across the World Trade towers and Notre Dame, as well as a scene that took place in an elevator shaft. Hull explains that this was a challenge due to the "confined con- ditions presented by the shooting space and the POV nature of the scene." According to Hull, "Previs for the two walks had to map out the beats of Philippe's high-wire performances, taking the character from A to point B, C and D across the historic steps of real events. This presented some detailed choreography and sequencing of what he would be doing when, whether kneel- ing, laying down or turning around. The shots that would ultimately be filmed had to have an emotional connection plus a feeling of conflict, danger and suspense. In the world of this movie, there were many creative options and opportunities to bring the viewer to the wire with the character, to pivot the camera or transition from above to below as he take these incredible walks over Paris or New York." For previs, The Third Floor typically relies on Maya for modeling and Motion Builder to use the realtime playback of the animation and camera capture. The stu- dio's postvis workflow includes tools such as Maya and MotionBuilder for modeling and animation, Boujou for tracking and Adobe After Effects for compositing. Suzanne Cipolletti, postvis lead at The Third Floor, says the studio's postvis artists were supporting the director, visual effects teams and editor by "turning around composites that replaced the greenscreen from the shoot with working visuals, backgrounds or set extensions. There were also instances where what was shot on-set needed to be re-envi- sioned or required additional previs to continue shaping the sequences, so it was possible to address this in the postvis phase as well. "Postvis was particularly important for the major walk sequence atop the World Trade Center towers, which was shot using a single practical rooftop that doubled for both of the skyscrapers. This meant there was a lot of greenscreen, with all of the final city elements — includ- ing the 110-story buildings, being created as completely CG effects by visual effects supervisor Kevin Baillie and the visual ef- fects team. So being able to visualize the towers and world around them through postvis and previs was an important step in evolving all the shots, as well as the director's final camera coverage." — Linda Romanello The Third Floor's Shawn Hull and Suzanne Cipolletti. The studio provided previs and postvis for The Walk.