‘Treasure’ holds a trove of effects

It’s never easy working for an exacting director, but visual effects supervisor Mitchell S. Drain says that his greatest challenge on “National Treasure: Book of Secrets” was keeping pace with Jon Turteltaub’s diabolical imagination.

“The whole film was continually evolving,” says Drain, who also worked on “National Treasure” alongside the filmmaker. “He would get inspiration as he saw each sequence unfold, so we tried to give him as many options as possible.”

In practical terms, that meant that Drain and chief executive/creative director Nathan McGuinness at Asylum Visual Effects had to create 700 FX shots (instead of the script’s original 180), though the film’s 14-week postproduction schedule remained unchanged.

While Industrial Light & Magic tackled some 200 shots, Drain compares the experience of producing so much work in such a compressed time frame to “a Vegas act, like having a dozen plates spinning at the same time. Our 140-person crew probably spent two years in manpower over that 14-week period.”

Asylum’s work ran the gamut from relatively simple wire removal to inventing full-blown CG environments involving no photography whatsoever, particularly in the sequences after Nicolas Cage’s Ben Gates and his team discover a hidden lake behind Mt. Rushmore.

To create the lake, the team married shots of Mt. Rushmore with shots of Sylvan Lake. The locations were 20 miles apart so matching the lighting was critical, as were some environmental cleanup -- removing all signs of civilization including roads and the crew -- and adding the rocky backs of the presidents’ heads.

The heroes find their way underneath the lake through subaquatic tunnels, but they soon are separated by an ancient booby trap. Cage, Ed Harris, Justin Bartha and Diane Kruger are caught on a 12-foot-by-12-foot platform, constructed from wood and vines, balanced on a single pivot point 80 feet above a pit littered with human skeletons. For the shoot, the actors stood atop a real platform on a hydraulically driven motion base 12 feet off the stage floor.

Asylum’s digital set extensions created the illusion that Cage and company were precariously balanced 80 feet above the pit. For wide shots looking up at the platform, San Rafael, Calif.’s, Kerner Optical built a one-quarter-scale, 20-foot-tall model, which was also used when it topples.

“Since the sequence kept evolving,” Drain says, “we didn’t strictly choreograph every movement. Instead, we tried to shoot every variation we could imagine so Jon [Turteltaub] had everything he needed.”

The Giant’s Causeway sequence -- inspired by the famed rock formations in Northern Ireland -- proved to be much more complicated, however.

In the scenes, Gates’ mom and dad, separated from the rest of the party, swing across a chasm to continue their journey to the center of the Earth. The first wrinkle: Actors Jon Voight and Helen Mirren lobbied to do the stunt themselves.

“You’d be surprised how spry and strong those two are,” Drain says. “The fact that they play their parts so convincingly and passionately made the sequence better.”

A small portion of the environment, featuring the octagonal rock spires unique to Giant’s Causeway, was built on each side of the soundstage with a rope-like vine hanging from the stage ceiling. The sequence was shot from two camera angles simultaneously as the actors performed against blue screen, where the size-to-be-determined cave would be added digitally.

“But once it was cut,” Drain says, “the Giant’s Causeway spires didn’t blend with the other underground sets. Jon asked us to re-create the environment. So Jon Voight and Helen Mirren are in a complete digital fabrication -- the area they’re standing on is the only piece left of the original set.”

It was the underground City of Gold, though, that turned out to be the most labor-intensive for the effects team.

As envisioned by production designer Dominic Watkins and art director Drew Boughton, the golden necropolis was too large to fit on any existing soundstage. Instead, the filmmakers opted to physically construct the parts of the set that came into direct contact with the characters on Universal Studio’s Stage 12, while the remaining 75% required digital set extensions.

“We shot with the intention of completing the background digitally,” Drain says, “but after the scene was edited, Jon decided he wanted a little more pizazz to the gold itself.”

Drain tried to simply apply digital paint over the City of Gold in each shot, “but the camera never sat still,” he says. “There was too much pitch and roll, and we needed a level of control on every piece of the set. Such is the state of digital effects these days that we went from just completing the environment to completely rebuilding the entire set digitally so that Jon could control the way the gold looked on a shot-by-shot basis.”

After Asylum’s lead modeler, Greg Stuhl, surveyed the entire stage and measured the one-twentieth-scale maquette of the environment, CG supervisor Jason Schugardt oversaw the tedious task of digitally re-creating every missing brick and piece of gravel.

“It had to line up exactly because we had actors standing on surfaces and picking up gold,” Drain says. “After we did the first shot, I consider it a compliment that Jon was pleased enough to make the entire set three times bigger than had been initially planned. It’s one of those double-edged things -- ‘Wow, we’re so happy you like the work that much to make three times more of it!’ So we created more temples, more destruction, more, more, more. It was a very daunting process, but we’re thrilled with the results.”