Entering Greengrass' Green Zone
"We put lots of tracer into the sky and flashes and extended the environment around to give lots of lighting onto CG trees placed around [the general's] house," explained Charlie Noble, Dneg's visual effects supervisor. "And at the end of the scene we rise up on a big crane move to reveal the iconic images of the 'shock and awe' bombing. And for those we referred very closely to the images we could glean from all the journalists who were holed up at the Palestine Hotel just over the river from the Green Zone -- the images that we all remember from the time. That gave us really good reference to how big the bombing was and the scale of the plumes of smoke rising up from the government buildings in the Green Zone.
Meanwhile, the interior of the Republican Palace was covered quite extensively. "We built the portico area and used the façade in Spain that kind of represented the footprint, just so it would give us clues what the lighting might be like in the strong sunshine," Chiang continues. "And then we literally built the whole environment down to palm trees and vehicles and the whole gamut of military arsenal. And we really used them in aesthetic ways and, in working with Chris Rouse, the editor, we figured out themes and what shots would be most effective to back up Paul's narrative."
While the Dneg team worked on previs for some of the big establishing shots, it was more feasible to take all the CG models with them on set where they were fed into a new realtime virtual overlay system provided by Stein Gausterade. Thus, at any given location they would align the relevant CG building to the set and then Greengrass and the camera team could pan/tilt the virtual camera around the set to see the extent of the intended additions.
According to Noble, practical framing/eyeline guides were also used. One example was for a shot of Damon's Humvee driving down the Victory parade underneath the iconic crossed swords, for which they employed a crane's arm to stand-in for one side of the swords as an eyeline guide for the cast and a framing guide for the cameras.
Matchmoving was essential, of course, to Greengrass' frenetic style, so Dneg matchmovers were on set, recording all the camera info. In addition, they developed a device that would record any zoom info, which was used about 90% of the time. "We attached zoom-encoded wheels to the cameras (that recorded the focal lengths for each shot) and then that data was sent back down the line to a laptop," explains Noble. "And then to help us out, the grips (known as Dragon Grips) offered to carry the laptops in their backpacks, making life a lot easier. This zoom encoder information played a crucial role allowing the matchmovers to snap the survey scene to the photography, giving them a head start, though it still presented a major job and some shots took several days to matchmove. The roto team also played a huge role as greenscreens were hardly used and most of the shots had to be rotoed extensively."