For most of the film's vfx work, elements of sets, vehicles or shots were captured on the set and combined with digital effects.

Another challenge came in extending the set of Aria itself. Designed as a giant cylinder with tens of thousands of glowing spheres, the practical set featured about 75 degrees of the overall design, up to a height of a few stories. Imageworks was responsible for extending that set to a full 360 degrees, which was difficult because the complexity of the set meant it was shot without a greenscreen or bluescreen.

"There was just a ton of roto to put the actual CG environment behind it, as well as painting out any lens flares and things that were bleeding through," Berney says. "There was just a lot of front-end work that needed to be done to track, roto and paint out on those shots."

On the backend, the new renderer Arnold was a big help. "We used it in the past on Monster House and it is being developed for future shows," Smith says. "But it was at a state where, because we had mostly hard surface models, that kind of thing -- buildings, tunnels, airplanes -- that we could take advantage of it and it really helped us match the kind of lighting we had on set here."

"With the Aria set, it's conceptually very straightforward: It's a cylinder and it's got 30,000 hemispheres that are glowing," Berney says. "My first reaction is, 'How are we going to achieve this in the rendering, do multiple layers, try to get the timing and the pattern and all that stuff?' We brought the Arnold developers in and I explained to them what we wanted, and they said, 'Yeah, just model it and just run it.' And I go, 'OK, will it take all day to render?' And they said, 'Not at all.' It's a pretty efficient renderer. You just basically model what you want in the real world and it's basically spot-on."

Berney goes a bit further, explaining: "It's actually calculating the energies around a scene and it's calculating pixels that way. So how that helps us now in our business and on Eagle Eye, as I said, you can actually model your lighting environment more toward the real world and you'll get better results."

"We had a lot of these pieces, and we had to match those right-on because they had to blend together," he continues. "Using this type of renderer let us get to those results more quickly."

Arnold supplemented Imageworks' use of Maya as its base tool, which is augmented with tools developed in house. Compositing is done with a number of tools, ranging from an in-house compositor to Shake and Flame suites.

Work on the film began in February and finished in August, with Imageworks doing around 280 shots. A base crew of about 30 people worked on the film, but they were frequently joined for short periods by specialists from Imageworks' talent pool, as needed.

Another difficult sequence involved inserting backgrounds in shots where a car is lifted up by a crane and in which the city skyline needed to be visible in the background. Berney says getting believable static tiles was a bit tricky.

"You don't have a lot of resources to pick up the kind of stuff you might want for an environment," says Smith. "What we end up doing is trying to do the best with [what we're given]."

The solution was to add some dimensionality to the background, enhancing it with various techniques, including reprojection, to get a believable result.

Smith says working on a project like Eagle Eye offers a nice balance to films where the effects are more visible to the viewer.

"It's nice to kind of balance it out with things that are subtle and people don't really notice," says Smith. "Then you know you've done your job."

Thomas J. McLean is a freelance journalist whose articles have appeared in Variety, Below the Line, Animation Magazine and Publishers Weekly. He writes a comic book blog for Variety.com called Bags and Boards, and is the author of Mutant Cinema: The X-Men Trilogy from Comics to Screen, forthcoming from Sequart.com Books.