In Richard Ayoade's new film, The Double, an over-looked and under-appreciated Simon James is usurped by his exact double, the confident and charismatic James Simon.

There's more diplopia to The Double than its doppleganger storyline though. The film is full of reflections and shadows that echo the narrative, as well as hints of the past that make up a vision of an alternative future.

It's a future that might have happened had technology not panned out the way it did - computers are the size of rooms, photocopiers are operated by specialist staff in dedicated offices, mobile phones do not exist.

There's a duality to the way the film was made, too. On paper, it's quite a lo-fi affair: based on Dostoyevsky's 1846 story of the same name, the film was shot on 35mm film rather than digital, is full of obscure film references and overlaid with a smokiness like smudged fingerprints on a screen.

It's not exactly the high-frame-rate photo-realsitic 3D filmmaking that Hollywood is into these days - and to describe it as 'refreshing' is to do a disservice to a film that goes all out to make you feel its characters' anxieties in as claustrophobic a setting as it could muster.

That said, The Double's darkened corridors are a nice change of pace to Hollywood's usual flood-lit effects approach but making the film required some pretty futuristic tech smarts from the company that put the visual effects together.

Gravitas

That company is Framestore, a visual effects and animation house whose most famous work was on last year's visual banger, Gravity. But intergalactic space thriller this ain't.

Framestore also has the advantage of having worked with Ayoade for ten years, from the days of Garth Marenghi, through his pop video career and into feature films including his debut Submarine.

None of those are titles exactly scream cutting-edge tech. Submarine was a straighter film than The Double, with life in suburban Wales needing fewer optical feats than a dark, dystopian demi-future, but it still took some ingenuity on the effects' part - like bumping some digital shots out to VHS then back just to capture the right kind of grain to fit Ayoade's vision.

But how do you handle a film shoot when your lead character and main supporting character are played by the same person? The major challenge was that Ayoade "didn't want it to feel like an effect." This meant there was no easy way out.

"Normally, a quick way round it would have been to shoot one actor on green screen and then key them off," Matt Clarke, VFX supervisor, explained. "But Richard isn't a fan of green screen anyway, because he often can see the spill and you find yourself obsessing about edges that are there that shouldn't be."

Instead, the scenes with two Jesses in were shot as though there were two actors on set, using a mixture of motion control cameras that can repeat the same move exactly multiple times, a body double and a technique called rotoscoping.

Rotoscoping is a 100-year-old process that basically now involves cutting out one Jesse Eisenberg and sticking him into a scene with the other Jesse Eisenberg. Every scene had to be shot twice very precisely, with Eisenberg using an earpiece to act 'against' himself.

The Double

"There was also talk of a CG head at one point," Clarke adds, casually. "We do have a scan of Jesse's head somewhere, but we never used it."

Framestore has built its own movie-making tech to create 3D scans, originally developed for last year's 3D effects behemoth Gravity. "We developed this thing where using a lot of cameras you basically take a photograph of every angle and it creates a 3D model from that," executive producer Simon Whalley tells us.

"And you've got all the textures because it's a photograph not a scan. So for production, it's much much quicker [than traditional scanning techniques]. The guys went down and set it up on set, so it took them half a day to get it all rigged up and ready but Jesse could just walk up, sit down, click and then he's gone. So it was as quick as that."

Real talk

But an animated head scan wouldn't have cut it because the technology is almost too good. "I think it just has to look real. It has to look authentic," Whalley explained. "I think if it was all digital and it looked authentic that wouldn't be a problem for Richard."

"You could do something photo-realistic in CG and it would look completely real but it wouldn't necessarily have the aesthetic imperfections of shooting the real thing, the nuances," added senior visual effects supervisor Paul O'Brien.

For a film full of retro-futuristic technology, it wasn't just the doubling that required lo-fi high-tech effects techniques. O'Brien, for instance, worked for weeks creating a 90s-style sci-fi TV show that appears for about 25 seconds in the finished film.

"All I knew was that I had about three or four minutes worth of this Replicator to create, and I didn't know anything about the film. I've got stacks of DVDs of The Trancer and Space 1999, and I'm going 'I don't understand how this is related - is this Dostoyevsky brought to the 90s?' I just didn't get it.

"So I'm slaving away and then I have a catch up with Matt and he shows me - he's taken maybe two seconds of my four minute piece and stuck it in a screen that Jesse Eisenberg's watching. And that's probably all he's ever going to use in the whole film - and I've been slaving away for a couple of weeks getting plastic shields to glow and all that.

"But most of our work is like that - you'd never even know it's been done. Set extensions and bits of this and that, all just to make it better."

The Double is in cinemas in the UK now and opens in the US on May 9.