Initially, Nolan wrote an 80-page treatment about dream-stealers. Originally, Nolan had envisioned Inception as a horror film, but eventually wrote it as a heist film even though he found that "traditionally [they] are very deliberately superficial in emotional terms." Upon revisiting his script, he decided that basing it in that genre did not work because the story "relies so heavily on the idea of the interior state, the idea of dream and memory. I realized I needed to raise the emotional stakes." Nolan worked on the script for nine to ten years. When he first started thinking about making the film, Nolan was influenced by "that era of movies where you had The Matrix (1999), you had Dark City (1998), you had The Thirteenth Floor (1999) and, to a certain extent, you had Memento (2000), too. They were based in the principles that the world around you might not be real."
Nolan first pitched the film to Warner Bros. in 2001, but then felt that he needed more experience making large-scale films, and embarked on Batman Begins and The Dark Knight. He soon realized that a film like Inception needed a large budget because "as soon as you're talking about dreams, the potential of the human mind is infinite. And so the scale of the film has to feel infinite. It has to feel like you could go anywhere by the end of the film. And it has to work on a massive scale." After making The Dark Knight, Nolan decided to make Inception and spent six months completing the script. Nolan states that the key to completing the script was wondering what would happen if several people shared the same dream. "Once you remove the privacy, you've created an infinite number of alternative universes in which people can meaningfully interact, with validity, with weight, with dramatic consequences."
Nolan had been trying to work with Leonardo DiCaprio for years and met him several times, but was unable to convince him to appear in any of his films until Inception. DiCaprio finally agreed because he was "intrigued by this concept—this dream-heist notion and how this character's going to unlock his dreamworld and ultimately affect his real life." He read the script and found it to be "very well written, comprehensive but you really had to have Chris in person, to try to articulate some of the things that have been swirling around his head for the last eight years." DiCaprio and Nolan spent months talking about the screenplay. Nolan took a long time re-writing the script in order "to make sure that the emotional journey of his character was the driving force of the movie." On February 11, 2009, it was announced that Warner Bros. purchased Inception, a spec script written by Nolan.
Locations and sets
Principal photography began in Tokyo on June 19, 2009, with the scene where Saito first hires Cobb during a helicopter flight over the city.
The production moved to the United Kingdom and shot in a converted airship hangar in Cardington, Bedfordshire, north of London. There, the hotel bar set which tilted 30 degrees was built. A hotel corridor was also constructed by Guy Hendrix Dyas, the production designer, Chris Corbould, the special effects supervisor, and Wally Pfister, the director of photography; it rotated a full 360 degrees to create the effect of alternate directions of gravity for scenes set during the second level of dreaming, where dream-sector physics become chaotic. The idea was inspired by a technique used in Stanley Kubrick's 2001: A Space Odyssey (1968). Nolan said, "I was interested in taking those ideas, techniques, and philosophies and applying them to an action scenario". The filmmakers originally planned to make the hallway only 40 ft (12 m) long, but as the action sequence became more elaborate, the hallway's length grew to 100 ft (30 m). The corridor was suspended along eight large concentric rings that were spaced equidistantly outside its walls and powered by two massive electric motors. Joseph Gordon-Levitt, who plays Arthur, spent several weeks learning to fight in a corridor that spun like "a giant hamster wheel". Nolan said of the device, "It was like some incredible torture device; we thrashed Joseph for weeks, but in the end we looked at the footage, and it looks unlike anything any of us has seen before. The rhythm of it is unique, and when you watch it, even if you know how it was done, it confuses your perceptions. It's unsettling in a wonderful way". Gordon-Levitt remembered, "it was six-day weeks of just, like, coming home at night battered ... The light fixtures on the ceiling are coming around on the floor, and you have to choose the right time to cross through them, and if you don't, you're going to fall." On July 15, 2009, filming took place at University College London for the sequences occurring inside a Paris college of architecture in the story, including the library, Flaxman Gallery and Gustav Tuck Theatre.
Filming moved to France where they shot Cobb entering the college of architecture (the place used for the entrance was the Musée Galliera) and the pivotal scenes between Ariadne and Cobb, in a bistro (a fictional one set up at the corner of Rue César Franck and Rue Bouchut) and then on the Bir-Hakeim bridge. For the explosion that takes place during the bistro scene, the local authorities would not allow the actual use of explosives. High-pressure nitrogen was used to create the effect of a series of explosions. Pfister used six high-speed cameras to capture the sequence from different angles and make sure that they got the shot. The visual effects department then enhanced the sequence, adding more destruction and flying debris. For the "Paris folding" sequence and when Ariadne "creates" the bridges, green screen and CGI were used on location.
Tangier, Morocco, doubled as Mombasa, where Cobb hires Eames and Yusuf. A foot chase was shot in the streets and alleyways of the historic medina quarter. To capture this sequence, Pfister employed a mix of hand-held camera and steadicam work. Tangier was also used to film an important riot scene during the initial foray into Saito's mind.
Filming moved to the Los Angeles area, where some sets were built on a Warner Bros. sound stage, including the interior rooms of Saito's Japanese castle (the exterior was done on a small set built in Malibu beach). The dining room was inspired by the Nijo Castle built around 1603. These sets were inspired by a mix of Japanese architecture and Western influences. The production also staged a multi-vehicle car chase on the streets of downtown Los Angeles, which involved a freight train crashing down the middle of a street. To do this, the filmmakers configured a train engine on the chassis of a tractor trailer. The replica was made from fiberglass molds taken from authentic train parts and then matched in terms of color and design. Also, the car chase was supposed to be set in the midst of a downpour but the L.A. weather stayed typically sunny. The filmmakers were forced to set up elaborate effects (e.g., rooftop water cannons) to give the audience the impression that the weather was overcast and soggy. L.A. was also the site of the climactic scene where a Ford Econoline van flies off the Schuyler Heim Bridge in slow motion. This sequence was filmed on and off for months with the van being shot out of a cannon, according to actor Dileep Rao. Capturing the actors suspended within the van in slow motion took a whole day to film. Once the van landed in the water, the challenge for the actors was not to panic. "And when they ask you to act, it's a bit of an ask," explained Cillian Murphy. The actors had to be underwater for four to five minutes while drawing air from scuba tanks; underwater buddy breathing is shown in this sequence. Cobb's house was in Pasadena. The hotel lobby was filmed at the CAA building in Century City. Limbo was made on location in Los Angeles and Morocco with the beach scene filmed at Palos Verdes beach with CGI buildings. N Hope St. in Los Angeles was the primary filming location for Limbo, with green screen and CGI being used to create the dream landscape.
The final phase of principal photography took place in Alberta in late November 2009. The location manager discovered a temporarily closed ski resort, Fortress Mountain. An elaborate set was assembled near the top station of the Canadian chairlift, taking three months to build. The production had to wait for a huge snowstorm, which eventually arrived. The ski-chase sequence was inspired by Nolan's favorite James Bond film, On Her Majesty's Secret Service (1969): "What I liked about it that we've tried to emulate in this film is there's a tremendous balance in that movie of action and scale and romanticism and tragedy and emotion."
The film was shot primarily in the anamorphic format on 35 mm film, with key sequences filmed on 65 mm, and aerial sequences in VistaVision. Nolan did not shoot any footage with IMAX cameras as he had with The Dark Knight. "We didn't feel that we were going to be able to shoot in IMAX because of the size of the cameras because this film given that it deals with a potentially surreal area, the nature of dreams and so forth, I wanted it to be as realistic as possible. Not be bound by the scale of those IMAX cameras, even though I love the format dearly". In addition Nolan and Pfister tested using Showscan and Super Dimension 70 as potential large format high frame rate camera systems to use for the film, but ultimately decided against either format. Sequences in slow motion were filmed on a Photo-Sonics 35mm camera at speeds of up to 1000 frames per second. Wally Pfister tested shooting some of these sequences using a high speed digital camera, but found the format to be too unreliable due to technical glitches. "Out of six times that we shot on the digital format, we only had one useable piece and it didn't end up in the film. Out of the six times we shot with the Photo-Sonics camera and 35mm running through it, every single shot was in the movie." Nolan also chose not to shoot any of the film in 3D as he prefers shooting on film using prime lenses, which is not possible with 3D cameras. Nolan has also criticized the dim image that 3D projection produces, and disputes that traditional film does not allow realistic depth perception, saying "I think it's a misnomer to call it 3D versus 2D. The whole point of cinematic imagery is it's three dimensional... You know 95% of our depth cues come from occlusion, resolution, color and so forth, so the idea of calling a 2D movie a '2D movie' is a little misleading." Nolan did test converting Inception into 3D in post-production but decided that, while it was possible, he lacked the time to complete the conversion to a standard he was happy with. In February 2011 Jonathan Liebesman suggested that Warner Bros were attempting a 3D conversion for Blu-ray release.
Wally Pfister gave each location and dream level a distinctive look to aid the audience's recognition of the narrative's location during the heavily crosscut portion of the film: the mountain fortress appears sterile and cool, the hotel hallways have warm hues, and the scenes in the van are more neutral.
Nolan has said that the film "deals with levels of reality, and perceptions of reality which is something I'm very interested in. It's an action film set in a contemporary world, but with a slight science-fiction bent to it," while also describing it as "very much an ensemble film structured somewhat as a heist movie. It's an action adventure that spans the globe".
For dream sequences in Inception, Nolan used little computer-generated imagery, preferring practical effects whenever possible. Nolan said, "It's always very important to me to do as much as possible in-camera, and then, if necessary, computer graphics are very useful to build on or enhance what you have achieved physically." To this end, visual effects supervisor Paul Franklin built a miniature of the mountain fortress set and then blew it up for the film. For the fight scene that takes place in zero gravity, he used CG-based effects to "subtly bend elements like physics, space and time."
The most challenging effect was the "limbo" city level at the end of the film because it continually developed during production. Franklin had artists build concepts while Nolan gave his ideal vision: "Something glacial, with clear modernist architecture, but with chunks of it breaking off into the sea like icebergs". Franklin and his team ended up with "something that looked like an iceberg version of Gotham City with water running through it." They created a basic model of a glacier and then designers created a program that added elements like roads, intersections and ravines until they had a complex, yet organic-looking, cityscape. For the Paris-folding sequence, Franklin had artists producing concept sketches and then they created rough computer animations to give them an idea of what the sequence looked like while in motion. Later during principal photography, Nolan was able to direct Leonardo DiCaprio and Ellen Page based on this rough computer animation Franklin had created. Inception had close to 500 visual effects shots (in comparison, Batman Begins had approximately 620) which is relatively few in comparison to contemporary effects-heavy films that can have as many as 2,000 visual effects shots.
The score for Inception was written by Hans Zimmer, who described his work as "a very electronic, dense score", filled with "nostalgia and sadness" to match Cobb's feelings throughout the film. The music was written simultaneously to filming, and features a guitar sound reminiscent of Ennio Morricone, played by Johnny Marr, former guitarist of The Smiths. Édith Piaf's "Non, je ne regrette rien" ("No, I Regret Nothing") pointedly appears throughout the film, used to accurately time the dreams, and Zimmer reworked pieces of the song into cues of the score. A soundtrack album was released on July 11, 2010 by Reprise Records. The majority of the score was also included in high resolution 5.1 surround sound on the second disc of the 2 disc Blu-ray release. Hans Zimmer's music was nominated for an Academy Award in the Best Original Score category in 2011, losing to Trent Reznor and Atticus Ross of The Social Network.