Case Study - Gravity

UK Screen member, Framestore, created the stunning visual effects on the award-winning movie, Gravity.

More than 400 Framestore staff worked on the movie for about three years, including making the pre-vis, filming and post production. The following describes some of that activity, which was an integral part of the whole film-making process.

 

Pre-visualisation

Meticulous pre-vis and planning took over a year prior to shooting. This was driven by:

  • Long shots of up to 12 minutes continuous shooting. The director, Cuarón, is known for long shots in his features. The team had to plan all the camera moves in these shots in advance to achieve the right creative result without the benefit of editing.
  • The location of the action in space meant that characters, objects and cameras could all move freely in any direction rather than being bound by set trajectories and by gravity. This enhanced level of freedom made the planning of camera moves significantly more complex.

  

The film was also lit in pre-vis by cinematographer Chivo Lubezki. This was a first for a live action film but necessary because of the extremely complicated shoots at Shepperton Studios.

 

Production

With pre-vis complete the combined team of VFX, motion control and physical special effects specialists set about creating the techniques that would help simulate micro gravity during the shoot, using a combination of motion controlled cameras and light rigs. The team developed an LED lightbox to surround the actors.

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 the cinematographer Chivo to light the actors which much greater flexibility than traditional film lights – the different colours reflecting off the Earth, moonlight, sunlight and starlight could all be replicated. Bullock would be strapped to a rig in the centre of the box as the camera moved around her, achieving the illusion that it is her that moves. It was a highly innovative, VFX-led filming process which resulted in a groundbreaking and critically acclaimed film.

‘We were providing motion control moves for the rigs but also generating a full immersive digital environment on-set using LED screens. Having to control that in real time was an interesting challenge! I don’t think there’s a 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.’ Chris Lawrence, CG Supervisor

Cuarón himself has said that he sees the technique as the next step in cinematography because of the amazing complexity of colour that LED lights can give.

 

Post Production

After a six month shoot the film moved into post production.

Modelling

Around 80% of the film is CGI, with the actor's faces often the only live-action elements in the scenes set outside of the space stations. All the movement, including the astronaut's limbs, hands and fingers was key-frame animated by hand. Inside the various spacecraft Sandra Bullock is mostly live action, but the set and props are still CGI.

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. 2,217 CG models were built. There are more than 30 million computer generated stars in the film's star field

‘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. 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.’ Charles Howell, VFX Producer

 Animation

For Cuarón accuracy was paramount. He wanted the film to feel like ‘a space documentary gone wrong’. The animation team had to completely re-learn their craft to cope with the physics of zero gravity.

‘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. 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, 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.’ Rich McBride, VFX Supervisor

As it was not possible to observe movement happening in zero gravity, much of the motion capture data was only used as reference. The vast majority of the animation was painstakingly key-framed by hand.

Amongst the many challenges, Cuarón needed a way of visualising flames and explosions in a zero gravity environment. As this is something that has never been seen by the human eye, the artistic interpretation of these unique moments in film was the creation of the VFX team, informed by their physics lessons at the whiteboard.

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