Making Space

Alfonso Cuarón's blockbuster Gravity has enjoyed fantastic critical success, collecting enough stars from film reviewers to fill the galaxy it so devotedly depicts.

It is, many say, the closest thing most of us will ever get to going into space. There's no time to think about it while you're watching the film of course, when you are immersed so deeply in the beauty and terror of space, but how were those stunning images made? By taking a film crew up 372 miles above the Earth? In fact, those mesmerizing images were planned and created in Soho, London. It's a Hollywood blockbuster made in Britain, from pre-production, through filming, to its extensive time in postproduction

"I first heard about Gravity at the beginning of 2010," says Visual Effects Supervisor Tim Webber, a long-time collaborator of Cuarón's and the man he approached to help realize a film no one knew how to make, "Alfonso came in and talked us through the movie for 45 minutes and it was gripping. We all came out really excited having heard it."

At that point it was unclear to what extent visual effects and Webber's team at Framestore would be needed. "There was a stage initially where it was going to be made with actors in real space suits," Webber continues, "they would have been hung up on wires on partial sets and we would have extended it and put in the background." In the end considerably more of it is CGI than first discussed, and in fact considerably more of it is computer generated than real.

In the majority of shots the only elements captured with a camera are the faces. The vastness of space, the Earth, the stars (all 30 million of them), the space shuttles, Hubble Telescope, the International Space Station (ISS), the copious and equally villainous fragments of debris, even the space suits: They were all made by visual effects artists at Framestore.

It was no simple process - everything had to be fastidiously planned. The first step down the three-and-a-half-year road to making Gravity's visuals was the previs, a basic animation process common to all films that blocks out the action in each scene before filming starts. But for Gravity it was anything but basic - it was meticulous.

"We spent about a year planning it before we shot it. By the time we turned up on set the film was pretty much locked," says VFX Producer Charles Howell.

Webber elaborates on the need for such a detailed plan: "It needed to be heavily previs'd for a number of reasons, obviously technically as we needed to work out the camera moves but also because when you've got a 12-minute continuous shot and it's set in space where you've got a camera that can roam absolutely anywhere and you've got people that can roam absolutely anywhere too - upside down, underneath, over the top, everywhere - the degrees of freedom are much greater. Therefore to design the shot creatively so that it worked without the benefit of editing [Cuarón is famous for his long shots] takes a lot of work, so previs was a big process."

It was lit by cinematographer Emmanuel 'Chivo' Lubezki during this period - an unheard of move for live action, but a necessary one ahead of a very complicated shoot at Shepperton studios. Even the use of stereo 3D, so often criticized as an afterthought, was planned during previs with Stereoscopic Supervisor Chris Parks. The original script did read 'Gravity: A Space Adventure In 3D' after all.

Sandy's Cage

With the previs complete, Webber and his accomplices set about creating the techniques that would help simulate micro gravity - cutting out the need for hundreds of trips in "the vomit comet," the specially designed aircraft that NASA uses to provide a few seconds of near weightlessness. Both Tim and Alfonso had been up in it themselves for research, but instead chose a combination of motion-controlled cameras and light rigs.

Collaborating with Bot & Dolly Motion Control and the on-set special effects team (the masters of physical, in-camera effects as opposed to the computer-based world of visual effects), cameras were strapped to huge robotic arms and George Clooney and Sandra Bullock were put in a variety of different rigs, many newly developed for the film. Then the solution of the lightbox was hit upon and the cramped LED box known on set at 'Sandy's cage' took over a large part of the filming responsibility. In its standard configuration, the box would be a 10m cube, with huge LED panels containing almost two million lights making up its walls. The use of LEDS allowed Chivo to light the actors which much greater flexibility than traditional film lights - the different colors reflecting off the Earth, moonlight, sunlight and starlight could all be replicated.

Bullock would be strapped to a rig in the center of the box as the camera moved around her, achieving the illusion that it is she that moves. The camera could zoom in and out from any position and it would race towards her and stop dead, just centimeters from her face.

It was a highly unusual, VFX-led filming process. "When I was on set with the lightbox and the robots I thought 'I've never seen a setup like this," says Framestore VFX Supervisor, Rich McBride. "I'd just never heard of anyone doing anything like it. I knew this film was going to be groundbreaking."

"We were providing motion-control moves for the rigs, but also generating a full immersive digital environment on-set using LED screens," explains CG Supervisor Chris Lawrence. "Having to control that in real time was an interesting challenge! I don't think there's great precedent of that being done before on a movie. At the time we did it I don't think anyone had done it the way we had with a box that completely surrounds an actor and having to bring live CG elements in."

Cuarón himself has said that he sees the technique as the next step in cinematography because of the amazing complexity of color that LED lights can give, so we may see the it become more common. After six months at Shepperton, the film was shot, but it certainly wasn't finished. Cuarón had captured the human performances - the raw emotions of Bullock's character Ryan as she tries to stay alive in an inhospitable place - now it was time to head back to Framestore to create the universe around her.

Physics Lessons

For Cuarón, accuracy was paramount. He wanted the film to feel like a space documentary gone wrong and for everything to be rooted in reality wherever it could be. "There was an awful lot of research to be done in the way things look and the way things work in space, the way things move," says Webber. "We had to retrain the animators to an extent as they are so used to portraying weight. It's one of the hardest things to portray and our animators have it in their blood. Then suddenly there is no weight. The physics of outer space are completely different, it's not just the zero gravity, it's the zero air resistance, and so once something starts moving it will keep moving and it won't ever slow down. Things like that. We had little physics lessons with a whiteboard and discussed the implications of the physics with Alfonso."

Webber continues. "He's is a stickler for reality up to the point where there is no other way. We went to every length to be real and to desperately find ways to fit in with the story in a way that was possible in space. But every now and then you have to break it. At one point we were talking to an astronaut about how a shuttle disengages and he told us that one initial process of it take four minutes. Obviously we weren't going to sit there for four minutes while something happened! That would make for a dull film."

Building the Galaxy's Biggest Junk Pile

One of the most difficult tasks was building everything. Just as they would be on a traditional set, every element had to be made in CG. "Building the space suits, the space shuttles, the Hubble Telescope, the ISS and everything else was a huge challenge because people know what they look like," says Howell. "The interior sets, which are all CG inside the ISS, were phenomenally detailed too, and every bit of that had to be modeled by someone. It took over a year to build everything. We never really stopped - we were constantly adding detail."

Leading this digital construction team was Ben Lambert, who is proud of the lengths they went to make the models as accurate as possible. "With the ISS in particular it's made up of around 50 modules, each sent up at a different time over the last 25 years. It's the galaxy's biggest jigsaw, but also its biggest junk pile - there's actually a lot of redundant technology up there. So we couldn't just throw a great big sci-fi kit all over it, make it look cool and put shiny chrome aerials on there. We had to source photographs really carefully. You could probably look at one of our interior shots and a photo of the ISS and work out what module the scene is in, it's that accurate."

Another demanding process was getting the faces shot at Shepperton to line up exactly inside their CG space suits - a difficult task even when the camera has been programmed. "You could plan an entire shot, but you couldn't plan exactly what Sandra was going to do once she was in the box," says Compositing Supervisor Anthony Smith. "It's like we made three films - we previs'd a film, we shot a film and then we made another that was based on what we shot. Everything had to be fitted to what happened on set."

When it comes to the animation some might assume much of the movement was achieved through motion capture, but as it was impossible to observe movement happening in zero gravity, much of what could be captured wasn't relevant, despite being very useful as reference. The vast majority of the animation was actually painstakingly key-framed by hand. It wasn't just the two actors that needed animating either: much like the Earth looming in the background, Gravity's camera is in many ways another character. "We spent as much time animating it as we did the astronauts," says Animation Supervisor Max Solomon. "It's used to disorientate the audience and to try and break the sense of there being an up and a down. We kept it shifting constantly."

A Long Shot

Alfonso Cuarón's characteristic longs shots made the whole process more difficult. A common remark from the VFX team is that there was nowhere to hide, no quick ways of establishing a shot - everything they created was on full display, maybe for ten minutes at a time. Their work had to stand up to intense scrutiny.

"The amount of planning and additional work that came about because of the long shots was enormous, it shouldn't be underestimated." says Chris Lawrence. After hitting a button the team would often have to wait more than two days to see if a particular simulation had worked. It wasn't just the long shots; the whole process took a very long time and an awful lot of computer power.

To render Gravity on a single core machine with a single processor in it and be ready for 2013 you would need to start before the dawn of Egyptian civilization. Renders rarely look right the first time and comments need to be given and addressed - typing into a program called Shotgun, Gravity's VFX coordinators wrote the equivalent of four copies of War and Peace while taking notes during feedback.

One sequence that had people tearing their hair out is ironically one of the film's most calming, when we see Bullock's character Ryan curled up in the fetal position, floating in the relative safety of the ISS. It was filmed with one of Bullock's legs strapped to a stool, with three robots, one for the camera, one to control a spotlight behind the ISS porthole and the other to move the porthole all revolving around her.

In the finished shot it is her that spins around, both legs free, removing a space suit, which never really existed. "It was one of the hardest shots," says Rigging Supervisor Nico Scapel. "We'd already built the suit, but now we had to take it off. We were really worried about it for a while." Entire sections of her had to be made in CG, including the leg that had been strapped to the seat on set, and there are countless techniques used at every point.

"It's always difficult when you have interaction with a live actor and CG dynamics because you need to match the movement with something that has been shot," says Simulation Supervisor Sylvain Degrotte. "I'd like to see what the audience thinks is CG and what is life."

"There are always bits people will assume are CG, like the wide shots of the shuttle, because they know it can't be filmed," says Webber. "But there are bits that people just assume have been filmed, for instance a mid-range shot when she's working on the Hubble [image above, right]. Lots of people have seen it and asked us what we did there - they had no idea that it's basically all CG apart from her face. It's like on Children of Men, [for which Tim supervised the delivery of a CG baby, and was nominated for a VFX BAFTA] when I last worked with Alfonso, when someone came out of the cinema saying something along the lines of 'I can't believe they got that woman to give birth on screen' and then you just think 'yes!'"

That's the aim for Gravity: that those years of extremely hard work by over 400 people went unnoticed and people walked out of the cinema wondering how they got a film crew up into space. That's when you know you've done a good job.