World Trade Center gives new perspective on 9/11. All images © Paramount Pictures Corp. Courtesy of Double Negative. 

For any visual effects artist, recreating a real life event is always a particularly challenging assignment. But when this event is as well documented and as deeply emotional as the 9/11 terrorist attacks, it can be a daunting prospect. When dealing with such an iconic moment in history, you should better get it just right… In World Trade Center (released by Paramount on Aug. 9), director Oliver Stone recreates the 9/11 tragedy from the perspective of two Port Authority Police Department officers who were trapped beneath the collapsed towers. Since the script is based on a true story, authenticity and accuracy were of paramount importance for the filmmakers. To recreate what happened outside and inside the World Trade Center, overall visual effects supervisor John Scheele split the effects shots among four vendors: Double Negative, Giant Killer Robots, Animal Logic and CIS Hollywood.

The visual effects encompassed three different categories of shots. The first one involved recreating the whole Lower Manhattan area, including the Twin Towers, in its pre-collapse stage, and then producing the raging fires on the Towers. In the second one, visual effects artists had to reproduce the collapse of World Trade Center, as seen from the interior of the buildings. The final category entailed recreating the post collapse environment. Since the collapse itself had been seen hundreds of times on television, Stone felt that it was not necessary — and probably not appropriate — to recreate it digitally. Instead, he preferred to focus on the point of view of some individuals and to show the events unfolding from their intimate, but truncated perspective.

Half A Million Reference Stills
Lead vendor Double Negative had the unique task of creating effects for scenes before and after the collapses, eventually producing 85 shots. Visual effects supervisor Michael Ellis and vfx producer Andy Taylor oversaw the project, with CG supervisors Peter Bebb and Ryan Cook handling the tricky 3D builds and smoke research and development. Double Negative started working with the production in May 2005. and provided a previsualization that was used for the New York shoot in October. A team was sent to New York to gather photographic material for reference. “The crew was never allowed to get close to the Ground Zero site to shoot plates,” Ellis recalls. “All the street scenes were actually shot in downtown Los Angeles. Greenscreens were used to block the perspectives, but we still had a lot of rotoscoping to do to be able to replace the environment with our CG Lower Manhattan. In fact, we not only had to recreate the Towers and the whole WTC complex, but also all the surrounding streets, which encompassed several blocks.

“Since we couldn’t shoot any plate, we decided to use the system that we developed last year for Batman Begins, in which Gotham City was basically built out from thousands of architectural still photographs. For WTC, we went out and shot over half a million stills from the area surrounding the Ground Zero site. We started by taking overall panoramic views of each street, and then moved on to photograph each building, using a 50-foot scissor lift to get a clear point of view. We shot 8.0 megapixel stills — with bracketed exposures — that captured 3-foot square sections of a façade. Back at Double Negative, we used proprietary software STIG to tile all the images together and remove the distortion. That allowed us to reconstruct each façade as a high dynamic range image that we could then project onto a corresponding 3D geometry built in Maya. In terms of modeling, we really focused our efforts on six or seven main buildings that were going to be seen up close.” All the CG elements were then rendered in RenderMan using Double Negative’s in house renderer management software dnRex.

In addition to the burning towers, the visual effects artists had the equally sensitive duty of recreating the rubble. Courtesy of Double Negative.