Aside from the development of the Limbo City shoreline procedural layout system, a key area of R&D was in lighting and rendering.

"Weightlessness was achieved through a clever combination of actors on wire rigs in a vertical hotel corridor set and a hand-operated seesaw rig on a horizontal version of the same rig," Franklin continues. "Joseph Gordon-Levitt trained intensively with Tom Struthers' stunt team for weeks with the result that he appears as himself in the vast majority of the finished shots. Double Negative 2D lead Astrid Busser-Casas and her team removed all of the wires and rigs, carefully rebuilding the sets where necessary. Costume Designer Jeffrey Kurland came up with fantastically stylish outfits that were also vfx friendly, adding little touches like stiffened shoelaces that didn't flop about giving away the direction of the vertical. One particularly demanding shot, which shows Arthur wrapping the dreamers in cable in preparation for their journey to the elevator, was shot in the hotel room set turned on its side. Numerous wires ran across the stunt actors' faces and CG lead Stuart Farley created digital doubles of Cillian Murphy and Ken Watanabe to hide the fact that the actors themselves weren't in the rigs.

"The elevator shaft was built as a horizontal set inside the vast Cardington hangar outside of London…Joe was suspended on a mobile crane rig, which ran on the same rails as the elevator, and Double Negative added flailing elevator cables and pyro hits to the scene where Arthur blows out the elevator's emergency brakes. Corbould's team rigged the elevator to blast along the rails, propelled by a compressed nitrogen cannon. During post, Chris Nolan decided that the shots looked more effective when turned on their side, so Dneg CG lead Alex Pejic created a detailed model of the elevator shaft to extend the set, filling in the gaps left by rotating the image 90 degrees."

For the snowy action sequence, Dyas' art department built a Fortress set in the mountains of Kananaskis County in Canada. CG lead Vanessa Boyce and 2D Sequence Supervisor Richard Reed created seamless digital extensions of the practical set as well as a fully CG version of the whole base for use in wide establishers. New Deal Studios provided a highly detailed miniature (supervised by Ian Hunter) and a pyrotechnic destruction that complemented the full scale demolition provided on location by Corbould's team. Numerous digital enhancements were added to the destruction, including extra debris, dust and collapsing tower structures. Both miniature and digital models derived their textures and details from the full-size set with a great level of integration being achieved as a result.

Later, as Cobb and Ariadne advance in Limbo City, they pass through a canyon-like street that was based on an actual housing estate in Morocco that resembled Bauhaus-style architecture. Dneg CG artists lead by CG Supervisor Alison Wortman and CG lead Becky Graham provided detailed building extensions and the vfx animation team added wind-blown clouds of debris to the streets. Deeper into Limbo, the narrow streets give way to open squares with colossal towers marching to the horizon. CG Supervisor Phil Johnson developed the structures from composites of un-built Utopian high rise developments designed by Walter Gropius (designer of the original Bauhaus), Mies van der Rohe and Le Corbusier.

"Inception raises the bar in a number of areas," Franklin concludes, "especially in photorealistic daytime environments and complex dynamics work. For me, it also marked a new level of interaction with the filmmakers where I was able to talk directly with Chris and the other department heads, which made a huge difference to the end result. From the point of view of Double Negative, I think Inception is the latest example of a developing trend in which filmmakers are approaching vfx studios directly to handle shows in their entirety rather than appoint an independent supervisor and break the work up across several vendors, which results in a far greater degree of integration between the vendor and the production than is possible with the old model. I think the results speak for themselves."

Bill Desowitz is senior editor of AWN & VFXWorld.