By Chris Heard
BBC News Online entertainment staff
Sci-fi adventure film Sky Captain and the World of Tomorrow is the first major movie to be made using entire sets created with "blue screen" digital technology.
The film's entire set is digitally created
The film, which has its UK premiere on Monday and opens there next week, stars Jude Law and Gwyneth Paltrow in a retro-futuristic thriller set in 1930s New York.
Paltrow plays reporter Polly Perkins, who joins her former love Sky Captain (Law) on a mission to stop a mad scientist's plot to destroy the world.
The pair battle giant robots on a trail that takes them from the frozen Himalayas to a prehistoric jungle island.
The cast filmed their scenes against a blue screen, and were later placed into fantastic settings with thousands of spectacular digital effects filled in.
First-time director Kerry Conran spent almost a decade working on the $70m (£39m) project, beginning with a series of storyboard drawings which he converted to digital images on his laptop.
After producing a six-minute short, the process was later refined and the still graphics animated to produce a rough 3-D video using digital actors, called an animatic.
As technical aspects such as the lighting, depth and composition were enhanced, a grid was created for each slot and mapped out on the blue screen stage floor.
Using acting doubles, the film was shot all the way through in a kind of "dress rehearsal" before Law, Paltrow, Angelina Jolie and others were brought in.
Once adjustments of angles and shadows had been made to produce a cohesive rough cut, the stars spent just a month on the shoot - far shorter than the time usually needed on location.
'Sea of blue'
The film's producer, Jon Avnet, said: "What was valuable with the animatics is that it showed the actors what the shot was.
"There was enough detail for Paltrow to understand exactly what was happening and that when she's stepping on dots, it's actually an entire plane."
Paltrow said: "It was a sea of blue, literally. It was blue everywhere, blue floors, blue walls with various dots in places to orient the computer."
Law said the process was not always easy: "It was difficult at times, but at the same time you also free your mind, and your art follows.
"We were really in this kind of make-believe world, anyhow. You could say it was kind of similar to doing theatre in empty spaces."
Angelina Jolie appears in a cameo role as Captain Franky Cook
Although computer-generated imagery has been a large part of the film industry for many years, this is the first notable film made entirely digitally with live actors. Only the items they touch are real.
Scenes in classic movies such as Star Wars and Raiders of the Lost Ark were made using the technology in the 1970s and 80s, while the combination of live actors and static sets has a spectacular heritage stretching back to King Kong and Gone With The Wind.
Sky Captain uses the technology to create a vintage sci-fi aesthetic drawing on the look of 1930s and 40s serials such as Flash Gordon, as well as classic film noir and the pioneering futurism of Fritz Lang's Metropolis.
Shot with high definition digital cameras, the stars are muted in soft focus to give them the textured look of black-and-white movies.
"It's so difficult to get the effects right that you tend to celebrate every shot you get done," said Mr Avnet.