Meanwhile, CIS was also given an elevator sequence in which Salt pursues the president down his secret bunker underneath the White House, which also proved more challenging and creative than anticipated. "We built a very small set for that at Grumman as well for three floors with bluescreen at the top and bottom," Breakspeare recalls. "The plan was to extend the elevator shaft up and down in the shots that we saw it.

"The elevator sequence was shot by Second Unit Director Simon Crane, so he had a very definite idea about how to shoot this and what Angelina could or couldn't do practically. And so she was put in a rig harness and did all her own stunts inside the elevator shaft, but what we found is that she looked like she was hanging from a wire, and some of the moves weren't as big as they could be because we didn't have a set that was big enough.

With a completely digital environment, CIS was able to move things around and make the elevator sequence more dynamic.

"We were faced with some difficult problems. Later on, what we had discovered is we had already built this elevator shaft in CG because we had to rebuild the top and bottom. We said if we're going to replace the top and bottom in CG, we might as well replace the middle as well because it'll be too much effort to match everything. Now that we have her in a completely digital environment, we were able to move things around and make it more dynamic. We experimented with the set and had her jump two or three floors down instead of one. She looked like she was really falling and did this in one shot and everyone loved this look, so, suddenly this six or seven-shot sequence became 35 or 40 shots and became a far bigger moment in the movie."

Other action was handled primarily by Framestore, supervised by Ivan Moran (there are 700 vfx shots total), including the assassination of the Russian president at St. Bart's Church in New York City.

"We shot the whole scene in St. Bart's Church, so we had to explode the floor and put in smoke and dust and debris and have people running," explains Grasmere. "We had to build a secondary set and do all the stunts and special effects and build an entirely digital floor of the pulpit matching it tile for tile and drop it back in with the shot at St. Bart's and have the guy fall through this digital environment and have it look like he's really there. We had to match lighting and get the digital elements to look photoreal and work out the CG destruction so it looks believable over a series of 10 shots."

Speaking of explosions, Moscow-based Tikibot was the third largest vendor, handling explosions, bullet hits, muzzle flashes and blood. Phosphene worked on set extensions and matte paintings; UPP in Prague did CG creatures, including butterflies for a poignant flashback.

"I asked them to photograph real butterflies at a butterfly park with a high-speed camera, and they 3D motion tracked the butterflies to come up with how they really fly and we applied that movement to our CG butterflies," Grasmere continues. "We had to hand-articulate where they could fly and add custom animation to their flight pattern. I think they ended up looking more real than a lot of CG butterflies."

Although there was a lot of wire removal, it wasn't the automated kind with Nuke. "Because Angelina likes to do her own stunts whenever possible, so scenes like a freeway chase where she was cabled to the truck, we didn't have control of it. And all that had to be rebuilt and they were hand-held, moving shots. Many rebuilds had to be done as full CG, including rebuilding her hair and part of her face.

Like Salt, there is obviously more than meets the eye.

Bill Desowitz is senior editor of AWN & VFXWorld.