How 'The Walk' VFX Team Re-Created New York's Twin Towers

The Walk Still - H 2015
Courtesy of Atomic Fiction

The Walk Still - H 2015

This story first appeared in a special awards season issue of The Hollywood Reporter magazine.

To re-create Philippe Petit's 1974 high-wire performance at New York's World Trade Center for Robert Zemeckis' The Walk, which is on the Oscar VFX shortlist, the filmmakers had to start from scratch since the twin towers no longer exist. For visual effects supervisor Kevin Baillie of lead VFX house Atomic Fiction (Montreal's Rodeo FX and Prague's UPP also contributed to the film), that meant extensive research and an unfor­gettable helicopter ride.

"We looked through thou­sands of reference books and photos from the library and called the New York Port Authority," says Baillie. "We also took a helicopter up and had clearance to hover over ground zero at the height of the former twin towers. I will never forget looking down at the memorial and the reflecting pools and the emotional impact of knowing that Petit had done that walk without safety gear was completely overwhelming."

Baillie, who has collaborated with Zemeckis since 2009's A Christmas Carol, worked at the director's ImageMovers Digital before co-founding Atomic Fiction, headquartered in Oakland, Calif., when ImageMovers shut its doors in 2010. For the largely virtual pro­duction of The Walk, his team had to digitally re-cre­ate the site — including the twin towers and its views of Manhattan as they once appeared. "It's completely digital; there's not a single piece of real footage," says the VFX supervisor.

Step 1: A stuntman on the wire on a mock-up of the top of the twin towers on a greenscreen set in Montreal.

Step 2: A 3D wire-frame model of Gordon-Levitt’s head.

To put actor Joseph Gordon-Levitt atop Petit's wire, the production built a portion of the top of the twin towers on a greenscreen stage at Mel's Cite du Cinema in Montreal. Instructed by Petit himself, the actor learned to walk a tightrope. The trick­ier stunts, like juggling on the wire, used either a stunt perfor­mer combined with digital-head replacement or a full digital dou­ble of Gordon-Levitt.

Pixelgun Studio, another startup formed by former ImageMovers staffers, handled the necessary scanning. Its system involved a rig with about 150 cameras that took shots of the actor with differ­ent facial expressions and also captured his skin texture. "That was important for close-ups. We are not just getting the shape of his face but also expressions and where blood flows beneath the skin," notes Baillie.

Step 3: The 3D model matched to the motion of the stunt performer, with Gordon-Levitt’s performance added.

Step 4: The finished shot.

The VFX team worked closely with director of photography Dariusz Wolski. For instance, the lighting on the day of the 1974 walk changed from sunrise to overcast clouds; and Legend3D, which handled the 3D. The film has roughly 826 VFX shots — a low number for a 123-minute feature — since, explains Baillie, long 3D shots were needed to "give the audience time to explore the scenes."

To control infrastructure costs, Atomic Fiction used its Conductor cloud computing software, allowing the company to scale up or down with computing resources as needed. To complete the 25-min­ute walk, plus an additional 15 minutes of VFX shots, 9.1 million hours of processing time was needed. Cloud computing helped the company save about $1 million on the production, shot on a lean budget of $35 million.