Eric Nash, visual effects supervisor at Digital Domain, has supervised three shows in the past 11 months: Rules of Engagement and two upcoming features, Red Planet and the Coen brothers’ Depression-era opus O Brother, Where Art Thou?. The latter project only called for some 30-odd shots, but many were difficult simply because they had to look absolutely real. Nash says it was fine with him, commenting, "That’s the stuff I enjoy the most. The flashy science-fiction stuff is less appealing to me, partly because I spent so many years working on the Star Trek TV shows. It’s a lot more challenging and rewarding to create effects that very possibly could be real; the bar is that much higher to make them invisible."

The Coens imagined using visual effects primarily to enhance a sequence here and there and to create a climactic flash-flood that saves the film’s protagonists from a triple-noose hanging. Nash acted as his own director of photography on the high-speed flood effect, which included a miniature cabin, trees and mountains in the background. Although DD’s modelmakers matched the live-action location built at Disney Ranch, the filmmakers ultimately preferred DD’s model to the real thing. "Originally, [cinematographer] Roger Deakins filmed a locked-off shot of the real cabin that they were going to show prior to the flood to establish the location, which we had to match," Nash recalls. "We told the Coens that the match would never be 100 percent, but that our miniature would be of high enough quality that they could use it for the establishing shot. They were very skeptical.

"In creating the miniature, we performed a detailed survey of the location and used some proprietary photogrammetry tools," Nash continues, "and I would say it was [an] 80-percent match. But when the Coens saw the model in the final take with the flood, they actually preferred it to their shot, and they wound up using the miniature for the establishing shot! Alan Faucher, George Stevens and their model crew did their usual amazing job."

To believably re-create the interaction of real water with the set, DD’s miniature was built at 1/4 scale on a 30-degree angle to keep the water moving toward the camera, which was tilted up at the same angle so the set would appear level. Special effects supervisor Peter Chesney provided a pair of huge dump-tanks set up on twin 60’ towers. On cue, the tanks released their 8,000-gallon payload, which completely flooded the 30’-wide x 60’-deep set and washed away the cabin, which was rigged with anchor wires from within to make it break up when it was hit by raging water. "The biggest struggle we had was getting the model to break into enough small pieces so that audiences would believe our heroes would survive," Nash admits. "We did three takes, and the third one was the best, but a piece of roof came right up to the camera and stuck on the protective glass! We had to do a bit of compositing work, cutting and pasting water to break it up so that the roof would look as if it got consumed by water as the camera was hit by the wave."

Nash set up two high-speed cameras running at 96 and 120 fps, respectively, to properly convey the scale of the flood as it engulfed the miniature landscape. "We were on the ragged edge because we were overcranking and needed a ton of depth of field from the foreground leaves to the deep background," Nash recalls. "We were outside in broad daylight, so we couldn’t add any more light. When we settled on the appropriate frame rates, the aperture was just barely holding enough depth of field. Roger [Deakins] shot the surrounding footage on Kodak EXR 5293, but we had to shoot on faster stock without an 85 filter and then compensate digitally. That was a tightrope walk."

Following a traveling, over-the-lip-of-the-wave shot looking down on our heroes, our POV is submerged along with George Clooney, who is shown in an over-the-shoulder shot as the wave slams into him. The underwater sequence was envisioned as and appears to be one continuous lyrical ballet. In actuality, it involved a painstaking compositing job with dozens of elements. "A banjo, a tire swing, picture frames, a gramophone horn and Clooney, as well as lots and lots of hair-pomade tins, were all shot underwater in Universal’s tank," Nash remembers. "Our animation team created a CG bloodhound, which was fun, and we added some digital pomade cans that we could put in specific places and choreograph precisely alongside the film elements of floating cans. The Coens wanted [the audience to] first see one can, then a couple more, with the volume of cans building and building until we get above the surface, where they’re all popping up out of the water.

"The real challenge for us was taking these varied underwater elements, which were all shot handheld and varied greatly in water color and value, and blend them with each other as well as with digital elements into one long, lyrical shot," Nash says. "Our compositing team of Claas Henke and Mark Larranaga did a beautiful job."

When Clooney, John Turturro and Tim Blake Nelson surface, DD was able to aid the key transition from underwater by reframing the shot to keep the horizon out of frame while the cans bobbed to the surface. "The sequence was shot in Super 35, so we had the extra image area to actually reframe the above-water shot as Clooney popped up," Nash states. "It looks as if the shot was operated that way, when in fact it was locked-off."

But the toughest challenge lay ahead: the actors were shot floating on a coffin in Universal’s tank, engaging in dialogue that lasts at least a minute, and everything seen behind them -­ the water, houses, and even a cow on a rooftop was entirely CG. "Because he was shooting on water and had to light the scene to be overcast, Roger Deakins used the biggest silk I’ve ever seen," Nash says. "It was like a roof that measured 120 feet across and 80 feet front to back, and it sloped right down to the waterline in the tank. The real water only extended behind them about 40 feet, and everything beyond that was digital, including the buildings and trees. The 3-D team, headed by David Prescott, fabricated all of the background elements and created the CG water, which had to blend seamlessly with the real water in the plate. We couldn’t use blue- or greenscreen because it would have reflected in the water.

"The camera was down at the actors’ eye level; their heads crossed over the silk and needed to be rotoscoped in order to matte them over the CG background. In long shots like that, [the matte edge] just begs to show off some chattering and little crawlies. An incredible amount of rotoscoping was done, but you’d never know it thanks to our paint and compositing teams."

Nash says he enjoyed paying attention to the nuances that make the Coens’ films so much fun to watch. "O Brother is a little movie, but it was a great experience because they are such a pleasure to work with," he concludes. "They’ve got the entire film in their heads before they show up for the first day of shooting. They know exactly what they want. They’re very reasonable and pleasant, their sets are very laid-back, and they do fabulous work. If I didn’t have to work with any other filmmakers for the rest of my career, I would be very satisfied just to work with the Coens."