Viewers of director Rob Cohen latest action pic Stealth may be forgiven for trying to fasten their seat belts while sitting in the theater, so heart-churning and realistic are the film’s visual effects. Contributing in no small part to telling this thrill-ride of a story about the exploits of an elite unit of navy test pilots is the work of Digital Domain’s Joel Hynek. According to Hynek, there are 50 minutes of visual effects in the film. A large portion of the work, he says, is total CG, encompassing both backgrounds and foregrounds.Hynek began working with Cohen at an early stage, before the film was even greenlit, to help the director sell his concept to the studio. Cohen’s vision drew on a very specific camera style, taking its cue from video games, as a way to involve the audience in the sequences. His aim was to draw the viewer into the experience of flying a jet fighter, in much the same way he approached car-racing in his earlier film, The Fast and the Furious. Although the stealth jets in the film are a futuristic construct, Cohen wanted them to resemble actual planes. He enlisted North Aviation designers to create the prototype of the “Talon,” to look similar to the swing-wing, hypersonic fighter-bombers with pulse detonation engines currently on naval drawing boards. Once the aerodynamic basics were achieved, the film’s production designer Michael Riva and a team of industrial designers refined the jet fighters into sexier, Hollywood versions. For the visual effects, CG supervisor Vernon Wilbert set to work on building all the flying vehicles. According to Hynek, an important consideration in designing the flying sequences included achieving a sense of geography—knowing where the planes were at all times as well as what they were doing. As an aircraft changes its position in space, backgrounds alter to match.For this, Hynek used a tool known as Tergen (terrain generator), developed in-house at Digital Domain, which “allowed us to create any background, to light it any way and to make any camera move.”This three dimensional CG terrain generator is designed to create virtual backgrounds using real digital elevation maps from satellite and aerial surveys. Tree line, snow and erosion of mountain terrain are all built into the actual program. Trees created in Side Effects Software’s Houdini were one element composited into the backgrounds for Stealth. Aerial footage shot from Learjets and helicopters was used for some texture mapping, and mostly used as reference and to intercut with the CG.“The sequence that most surprised me and that I was worried about was the death of Henry [one of the characters],” says Hynek. The sequence was well underway when director Cohen switched from a design concept that was based mostly on plates to one that primarily used the Tergen. The CG terrain team was led by Digital Domain’s Brad Herman.To fly both artificial intelligence-based craft and the Talons, the film’s special effects expert John Frazier designed a special gimbal—one with five different axes instead of the normal up and down motion—to allow the plane to incline at different angles in all directions and execute the kinds of turns typical of fighter jets. Weighing around 100 tons, it was able to achieve a very wide range of motion and pull up to five Gs, explains Hynek.For the hundreds of live-action cockpit shots, an 18-foot nose section of the Talon was attached to the gimbal. This section was then “flown,” giving the actors inside a realistic feeling of flight. The moves for the gimbal were achieved in two ways. Based on the previs, the computer could generate moves. The moves could also be achieved manually by experienced fighter pilots actually flying in a flight simulator connected to the gimbal—when the pilots banked, so did the Talon in the gimbal.Cinematographer Dean Semler, ASC was responsible for all the live-action shooting. Three cameras were used to capture the footage, and he used a TechnoCrane and a Spider-cam—a camera device supported by four towers that can move anywhere in 3D space. In postproduction the camera moves could be used to move around the planes or for specific plane movement. Hynek was responsible for the aerial photography, including the nose-cone camera used to simulate the point of view of the pilot. He also shot backgrounds on the aircraft carrier. These backgrounds were used as plates when the Tergen was not used. All shots were re-animated and the airplane motion was refined in post.Hynek believes there were several areas where his team really pushed the envelope in terms of new ground in visual effects creation. These include the CG terrain generation, Digital Domain’s signature free-form camera style and the plane dynamics. Advances were also made in cloud generation using a 3D volumetric renderer cut with aerial clouds or plates. Foreground, mid and background planes were necessary as reference points to accentuate speed in flight sequences. Computer graphics supervisor, Markus Kurtz, developed CG fire used in the mid-air fuelling station sequence for the fuel cloud, fire and explosion. Although most of the fire was computer-generated, actual physical fire elements were added to relieve the CG of uniformity problems. Hynek describes this as the most challenging sequence. “It was the first started and the last finished,” he says.Other sequences of note include the imploding building in the opening mission. A 55-foot model was built for the building collapse with the rig as half of the construction. The diving down sequence to drop the bomb used aerial plates to achieve the stomach-churning free-fall sensation.Hynek was on the project for two and a half years, as close to job security as any freelancer can get. All in all, the Digital Domain team created 660 shots. He gives special commendations to compositing supervisor Bryan Grill for his “amazing work” and digital effects supervisor Kelly Port for her ability to divide up the enormous amount of work and keep the pipeline flowing. Wire removals and other optical-type effects were subcontracted out to Pacific Title Digital. Animal Logic created the free-falling sequence where a pilot has to eject from her fighter. Hynek concludes, “Rob was a great guy to work with, involving all the artists. He had the ability to pull out the best in everyone.”
Written by Mary Ann Skweres
