Hoover says the production did exhaustive research of what Berlin's buildings looked like in 1943. If background buildings visible in a shot weren't from the period, Sony Imageworks' digital team removed them and painted in authentic- looking buildings based on research photos. Additionally, Hoover asked matte painter Robert Stromberg to do a matte painting for the ceiling of a famous bombed-out church. (Stromberg, an Oscar nominee for his work on Master and Commander, had previously contributed to effects that Hoover supervised for Seabiscuit.) For this film, Hoover explains, "The roof of the church had been blown away, and people had cleared away the debris and held candlelight services. We had historical photographs, and Robert's matte painting was based on that."

Sony Imageworks built a Maya version of Tom Cruise's hand and then rotoscoped everything he did, frame by frame, to erase the "missing" fingers. Boujou was used to track the digital hand in the plate photography.

Greenscreen techniques were actually used sparingly, according to Hoover. "There were some buildings where the entrances weren't true to the period. We put up greenscreens so we could replace them with digital versions that were historically correct. But that was pretty minor." And greenscreen was decidedly not Hoover's choice when it came to the tricky business of altering Tom Cruise's hand to appear to be missing two fingers. "I had tried little green sleeves, but they spilled green on the fingers we wanted to keep," he says. "I'd much rather keep greenscreen and bluescreen out of shots if I possibly can. It just ends up looking more realistic. In this day and age, with the level of resolution that we have and the criteria of audiences, it's what you have to do. The only thing I did for the shots showing Tom's hand was to have his makeup artist paint two lines on his fingers where they would have been cut off, using a shade of makeup that matched the color of his skin when it was in shadow."

When the footage got to Sony Imageworks, the digital team built a version of Tom Cruise's hand and then rotoscoped everything he did, frame by frame, to erase the "marked" fingers. Hoover remarks, "It was probably, in a subtle way, the most spectacular work that we did. We rotoscoped Tom's every movement -- while he's building bombs, signing his signature, answering the phone and handling a gun. There were a lot of close-ups where we had to roto every finger and carefully blend between his real hand and the digital hand. I kept as much of Tom's real hand as possible. On a shot by shot basis, it was a different process."

Once Sony Imageworks had rigged the digital hand, they tracked it in the plate photography using boujou. Hoover explains, "Once the tracking was done, we did a proof-of-concept match move. Because it's really on a 2D plane, it's hard to tell if the hand is actually in the right position in three dimensions. So we had to pose the hand so it looked perfect to the camera. Then we'd load it into the computer and spin it around and if it looked all twisted in that position, we'd know it really wasn't right. It took a ton of very delicate, specific tracking."

For Hitler's Bavarian residence and headquarters, The Berghof, Imageworks built the exterior digitally and matted it into plate photography of a ski area in Austria. 

Hoover observes, "Tracking is one of those frontiers that everyone takes for granted, but actually it is quite an important step. You're building the foundation of the shot. So if it's not really right you'll see problems during rendering and have to start over. You can get it 80 % of the way and think 'It's going to be fine.' And then you render it and see all the problems. So you just have to work and work at it to get all those subtle things right."

Because there were a lot of extreme close-ups of Von Stauffenberg's scarred hand, the texturing was crucial. (Sony used Maxon Body Paint along with Flame tools to achieve these looks.) Hoover says, "The scarred hand is quite important to the character, and Bryan and I came up with some rules of what to show the audience that would be tasteful. We had a lot of photographs of what the scars would actually have looked like, based upon what the surgical procedures were in 1943. We followed that quite religiously. On a shot by shot basis we delicately dialed up or down how rough or detailed his hand appeared to be."

Cruise himself conferred with Hoover before scenes in which his hands figured prominently, asking to be told if he was moving his hands in ways that would make the post process more difficult. But there was no getting around this effect, especially in post-surgery scenes where Von Stauffenberg struggles to dress himself only using three fingers. Or where he intertwined his remaining fingers with his wife's hand during a dance sequence. Hoover says, "We know from historical accounts that Von Stauffenberg didn't stick his hands in his pockets to try and hide his injuries."

Because this visual effects requirement was so central to the character and so pervasive, it meant than this "non-effects" movie wound up having a subtle visual effect in many, many shots. "We touched about half the movie," Hoover says. "But I don't think anyone watching it will know that -- at least I hope they don't!"

Ellen Wolff is a southern California-based writer whose articles have appeared in other publications, including Daily Variety, Millimeter, Animation Magazine, Video Systems and the website CreativePlanet.com. Her areas of special interest are computer animation and digital visual effects.