"The White House is an icon," asserts Robert Grasmere, the overall visual effects supervisor, who describes the action as hyper-real for the Philip Noyce-directed Salt. "It was a pretty daunting task because we couldn't shoot at the White House or build a set or even put up bluescreens. These were front and center shots. So the work CIS did looks pretty real -- it all came through."
The reason it all came through is because of CIS' skill and visual effects repertoire. They shot the Grumman Air Force base and constructed two White House gate posts in the parking lot with gates, and then dressed up the ground a bit, added some grass on the other side of the fence and marked out with chalk the general curve of the road that goes in front the White House. CIS shot everything in one night and had their plate.
"We got the plates back and quickly worked on a temp version while working on the textured version that looked like the White House after we'd gone to Washington DC and taken hundreds of photographs," explains Mark Breakspear, CIS visual effects supervisor. "And we used that to build our model. Version two looked real. We refined it and put in digital trees and a complete synthetic skyline of Washington. We added digital humans, so we dressed up a couple of CG characters in security and army uniforms and then walking up the steps to the portico of the White House. "
Of course, because they were only using the north side for the action, CIS didn't bother building the other side in CG. That is until they decided to re-shoot the ending to relocate this crucial sequence on the south lawn. "So we had to now build it," Breakspeare continues. "It was probably the most inefficient way to build a model in CG, with putting all of your forces off to one side and thinking you're done and then going back and rebuilding the backside.
"It was much harder because it is a lot bigger and your closest vantage point is right on the bottom. We ended up going up the Washington Monument because there's a good vantage point from the top. We worked with the Secret Service to get special permission to take our photos with a tripod."
Salt has been captured and is taken away in the helicopter outside the White House. This raised several issues: we see all of Washington DC behind the White House, so CIS opted to do brute force with roto. It was too expensive to do a complete 3D model of the city, and a matte painting was going to look too flat.
"We came up with a clever way of accessing a free data set available from the US government, which told us where all the buildings were," Breakspeare adds. "We realized that if we were take images from the right angles and project them onto the boxes from the data set, we would get a very convincing cityscape night shot in 3D. One of our programmers wrote a plug-in that would take this government software and reconfigure it into useful geometry that we could use. We did a very simple 2.5D model of Washington DC going back 20 miles with simple geometry and simple textures, but it rendered quickly. He populated the streets with cars and headlights and rendered that as a separate layer."
They used Maya  for the animation but switched mid-stream from Shake to Nuke  for the more complex compositing. Since the facility was transitioning anyway to Nuke, it seemed like the best solution. "On paper it was suicidal," Breakspeare notes, "but we had played our hand and it turned out surprisingly painless. Nuke is amazing and, quite honestly, if we had tried to use Shake for the second half of the project, it would have come up short."
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.
"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.