"Hancock" Wreaks Havoc, On and Off-Screen
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Stormy Weather

Even more gratifying for Hahn, was a scene described in the script with one sentence: "Hancock and Mary [played by Charlize Theron] duke it out on Hollywood Boulevard." It sounded simple, but as the two engage in battle, they conjure up elements, like tornadoes and lightning that represent their respective mythologies. And these elements were left up entirely to the VFX team to render.

Charlize Theron, as "Mary," gets ready for an epic battle with Will Smith on Hollywood Boulevard. Image courtesy of Sony Pictures.

"John Dykstra, Visual Effects Designer, was overjoyed," Hahn remembers. "These elements weren't represented in an animatic, they weren't created by the production design department." Knowing that the visual effects team would be solely responsible, John wrote a five-page treatise on what the elements should look like as the scene unfolds. "First, we wanted the elements to represent the characters," says Hahn. "John wanted a certain motion and life to them. Since the characters are battling, he wanted the elements to be ominous, but with an outer shroud that was beautiful and graceful."

For the Hollywood Blvd sequence, Hahn and Dykstra worked with cinematographer Tobias Schliessler to shoot additional under-exposed passes, along with the native 35mm footage shot under clear blue skies. These passes would later be used by the visual effects team to manipulate the photographed plates since the changing weather conditions were added in post. "This usually makes DP's [directors of photography] nervous," Hahn acknowledges, "because the dailies [film developed and screened on a daily basis] look dark, but we needed the plate a little darker to make the virtual lightning and tornadoes work." In addition, "thousands" of digital stills—above and below key settings in HDRI format (High Dynamic Range Imagery)—were shot, which gave the team enough digital information to re-create the in-camera environment in the computer.

This contact sheet and video show the progression of the creation of this sequence. Image and clip courtesy of Sony Pictures. (Click to download video or right-click to download.)

"We wanted everything to look seamless and invisible," says Hahn, who, together with Dykstra, studied footage of actual tornadoes, a la The Wizard of Oz. "But John reminded me, we weren't in Kansas any more," says Hahn. "Hollywood Boulevard is not an expansive Kansas prairie." The first order of business was to create the wind and its virtual impact on everything in the vicinity, including Hancock and Mary. "There were two 15-foot fans blowing on set, but they barely ruffled Charlize's hair in the practical plate," Hahn chuckles, "so we had to add virtual, gale-force winds to the initial composite." Hahn says his team "wrote a fair number of extensions for the plug-in architecture of Houdini and Maya" to intermix lightning with dark frames illuminating particulate matter. "Our director would see the animations and say, 'more threatening, more threatening!'" But, ultimately, he was very happy with the end result.

Cut to the Chase

As proud as Hahn is of the visual effects department, he gives props to his practical brethren in special effects on one scene in particular: the spectacular SUV chase sequence. (Special effects are created on set, in camera through make-up, prosthetics, and stunts, while visual effects are created in computer, during post-production.)

The scene starts with a visual effects gag: Hancock flying after the speeding SUV and landing in the back. Well, not so much flying—gliding heroically, like other superheroes—as hurtling haphazardly, crashing through a road sign before plopping in the back of the speeding SUV. "We shot Will Smith on a wire, against a green screen," explains Hahn, who admits that wire work has its limitations. "The body doesn't hang in space the way it would without the wires," he says, even with computer-controlled winches. According to Hahn, the kinetic motion the director wanted was lacking, so the VFX team created a CG Hancock for the opening section of the scene.

Video still
Hancock took flight through a combination of practical effects, including wire work, and visual effects such as green screen. (Click to play video in a new window or right-click to download.)

"The rest of the SUV chase sequence was done practically, through amazing coordination and choreography between the special effects department and stunt teams," says Hahn. Fourteen cameras were set up on the 105 freeway in Los Angeles, half of which were remote-controlled, to capture all of the action in a single take. "Everything was rigged," Hahn recalls. "A chase van followed the picture car [the car, or SUV, that would appear on camera]. Anyone who was not needed directly on set was at a remote location about a quarter-mile away. Logistics were mind-boggling." Ordinarily, Hahn and his team would get camera and lens information for each camera, "but it was so crazy that day, we gave it up to God!" Though there was some augmentation, or digital enhancement, in post, by and large, the scene seen on–screen was captured in camera. "We color-corrected [digital manipulation of the frame] to maintain consistent daylight, since the set-up took all day, from sunrise to sunset to shoot," says Hahn, "while on-screen, elapsed time is only a minute or two."

Hancock Image
According to digital effects supervisor Ken Hahn, actor Will Smith understands the technical challenges of making an effects-driven film like Hancock. Image courtesy of Sony Pictures.

3D in Stereo

With a well-deserved break after his work on Hancock, Hahn looks forward to catching up on the all the latest technological advances in his field. Looming largest: the transition from 2D composites to 3D, "stereoscopic" finishing. "Even though much or our work in visual effects is done in 3D, creating 3D objects or characters," Hahn explains, "the finished project is composited into two dimensions for release on traditional theatre screens." But that's changing, as more and more filmmakers, such as James Cameron, shoot films, like the upcoming Avatar, stereoscopically—in 3D, requiring 3D glasses. "Yep, just like they used to wear in the 50's," laughs Hahn. "Which I find the biggest impediment to its success. I won't wear them."

"It's a whole, new way of thinking for VFX artists and technicians," he adds, "especially the layering aspects. Your eye is always trying to converge on something, and in 3D, we have to fix that convergence point." According to Hahn, the bar will be higher for visual effects finished in 3D. "We have certain 'cheats' with 2D composites," he says. "With stereoscopic finishing, we won't be able to 'paint-fix' our way out of things, because the eye will see artifacts or warpages." As a fan, though, Hahn acknowledges he would like to see his favorite comic book films, like X-Men, in 3D. Even if he has to don the dorky glasses.