CGSociety :: Production Focus

11 October 2013, by Paul Hellard


Alfonso Cuaron has soared to new heights from the days of his celebrated 'Children of Men' in 2006. As a life-long, self-confessed 'space fan', Cuaron has been hoping to create this movie for longer than technology has been around to have it created. There are echoes of James Cameron holding onto plans for Avatar until the stereo tools were available.

In his newly released GRAVITY, Alfonso Cuaron called for high resolution animated previz to be the basis for the majority of elements in his story. The Shuttle spacecraft and the International Space Station (ISS) are right in the way of a stream of space debris. This ultimately destroys the craft and brings on the ultimate challenge. This premise points to a fair percentage of CG being required from the start.

I caught up with Framestore VFX Supervisor Tim Webber on the phone this week, standing outside the front of the National Film Theater in London. He tells me he first had a meeting with Alfonso Cuaron about GRAVITY in late 2009. "He'd not written the script but he was very clear about the story," says Webber. "It was pretty intense even back then, him talking through the story and in many ways it hasn't changed, all the way to the screen." Framestore and the surprisingly few studios were assigned to the VFX work, to create this unique cinematic masterpiece. Not a science fiction so much as a space drama.

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Completely new techniques were required to pull off this very real looking drama in space. In keeping with Cuaron's style, the opening shot was 13 minutes-long, instantly pulling the audience into the drama. This new tech were brought into play to create the stage of zero gravity. "The previz was a pretty intense process," understates Webber. "It had to be created to an advanced stage and then used to illuminate the faces of the actors as they are seen floating outside the Shuttle holding bay in orbit." This stage was almost entirely CG. in fact, everything but the faces of the actors in the helmeted visors. Even the fingered gloves of the crew fiddling with the computer board before the drama begins, were rendered to the appearance of being completely real. But they weren't. "This was mostly keyframe animation, while there was some motion-capture at some stages as well," says Webber. "Of course, it's really hard to use motion capture to depict a zero gravity environment, but again, we could have done small mo-caps and spent all that time on it, but then you'd have to fit it into the shot and keep it looking natural."



One of the main rigs was used on GRAVITY was based on a camera robot arm and the LightBox. Moving the lights on the robot arm was proving cumbersome, so the actors were moved inside the LightBox and this was moved around them, with the least movement to them as they could muster. "We came across a company called 'Bot&Dolly' that shot ads in San Francisco," explains Webber. "They put a camera on a robot. This was a similar robot that was used to assemble cars and furniture in a factory. It was a bit like a motion capture but with more flexibility and more speed. We added extra features as well, and everything was computer-controlled. Everything was being run off a 'platform of geeks', as the cinematographer always called it."


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The Previz of 360-degrees of the surrounding sunlit station, crew and planet Earth was created to either be full rez in the shot, or projected onto the face of the actors in shot, used as a precise reference to induce inferred insitu lighting. "We had Previz not as you would normally do, so you could generate an idea just of what the shots are," says Webber, "but almost into full animation in some parts. We wanted to take most of the movement off the actor so when they are shown 'upside down' they wouldn't have their veins up and becoming all red-faced, which is what happens in real gravity. We need to keep the actors at all times, reasonably vertical. So, that was the reason most of the movement was done by the camera."

Another rig used to keep the actors was the TiltPlus rig, in which they stood, which allowed Framestore to tilt them a few degrees forward and back, giving the crew quite a lot of control, and a degree of comfort to the actor.

Other pieces of action in the movie were not required to be animated, as they would only be required as a lighting guide. Webber says the difficulty was that with performances, they had to be exactly right, or the angles, lighting and even prop placement would be incorrect. "You have to get all the subtleties pinned down, particularly because of the long shots, before you can commit to the broad strokes of a lot of this. It was really critical. If an actor does something slightly different along the way, will interrupt what they have to do later in the shot."

In order to run the Lightbox and the other various methods Framestore used, they had to create the Previz, get all the action and the camera moves pinned down. They did a pre-light as well, just to pin down the performances as much as possible.

There is a scene with Bullock, where she takes her space pressure suit off and curls up in the foetal position in the circular door frame of the ISS, floating in zero gravity. "There was just nowhere to hide the rig really," says Webber. "One of the rigs we came up with was a bicycle seat and it had to show minimal impact on her body. As she was quite a few feet up in the air sitting on the seat, we had to digitally replace a lot of her legs and hip, as we cleaned up the rig.

Each individual shot had its own unique set of challenges. When she was flung away initially from the Shuttle, while on the satellite arm, the lights are spinning around, as are the backgrounds also changing. The sun is setting so the colors are changing at a prescribed rate. The Shuttle, Hubble and surrounding debris is in the background, as is the curvature and detail of the vast Earth. All these images having to be choreographed between what is going on on her face, the lighting on the suit, making sure it all looked aesthetically pleasing at the same time."



Tony Clark was the VFX Supervisor at Rising Sun Pictures in Adelaide Australia. He oversaw the production of 17 shots, near the end of the movie GRAVITY. He first had the flag up for the job in mid 2010, for 15 months. From late 2010 through to the end of 2012.

Rising Sun Pictures (RSP) contributed 2.5 minutes of footage to the climactic end sequence of Gravity. The stereoscopic, fully computer-generated shots included hard surface space station & re-entry vehicles, plasma & flame effects, some destruction, earth environment, atmospheric effects, parachutes and digital matte paintings. "This is from when the Sandra Bullock character arrives at the Chinese space station called the Tiangong, through to when she splashes down in the water on Earth in the Shenzhou capsule. If you look at that sequence, it's all the exterior shots," says Clark.


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RSP collaborated with Framestore, utilising their look for the film and rolling that in to the RSP assets. Additionally the RSP team sent high resolution cameras up in to the atmosphere on a weather balloon to capture low orbit reference photographs, which were later included as part of the digital matte paintings for the environment.

"We never really had any idea of what the rest of the work looked like until about halfway through our schedule," Clark confirms. "Framestore was clearly pushing really hard, though it was very early days in terms of R&D for us as well. When they sent through a 'style-frame' of what it was looking like, it was clearly very detailed. It was a shot of the Soyuz station orbiting the Earth, heavily backlit. We could see from that shot that it was going to be something extraordinary."

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While Framestore did their rendering in their proprietary engine Alfred and Arnold, the render engine of choice for RSP was Houdini Mantra. They spent a long time building detail and matching the looks as per the Framestore direction with Tim Webber at the helm.

Framestore's pipeline is famously enormous. RSP took the asset for the Tiangong which Framestore were using for a couple of shots. They brought that asset into their system. This one asset had thousands of textures and millions of polygons: a very dense model. The entire model was highly appointed in physically-based lighting.

In this physically-based rendering model, some incredibly significant reflectance calculations are being generated. "It's like ray-tracing, but on steroids," says Clark. "We were originally looking at times of many days to render, but with many, many months of optimising, in the end we got that time down to close to 12 hours. Bringing these times down took some deep study of the elements of each shot. Knowing where the important detail is. We're actually really lucky to have a great team of artists and technicians who can pore over a machine and look what's going on. We quite literally had people working on the lighting and optimisation of the renders for months. These are all costly shots to execute because of the level of detail that everybody wanted to achieve."





In the first wide exterior shot of Sandra Bullock arriving at the Tiangong in low Earth orbit, we are starting to see light streaking from the extremities of the solar panels and antennas being buffeted around. This is plasma, flames being generated off the sharp edges of the large, gangling space craft. This whole structure is still in orbit, but hitting the upper reaches of the atmosphere, going at tens of thousands of kilometres an hour. As the sequence progresses, the effect needs to become more pronounced. More immediately violent and hot, around the edges, some parts are actually being shaken out of place and being ripped away. This revealed a whole range of internal geometry that RSP modeled and placed in situ. What made the lighting of this sequence an even complex challenge for the RSP crew was that there was an additional balancing act. The sun was rising over the vast crescent Earth in the background, with all the complex mountainous and cloud textures and cities rolling underneath. There were a number of conflicting effects going on in the one shot.

Re-entry of a spacecraft is something that everyone know happens, but no-one has been able to film it from outside the craft, as we all know. There's nothing on YouTube other than earth-bound shots of Skylab breaking up and some shuttles on their way in. Creating this for a movie is open to interpretation, which makes for an extra challenge. "What does 'real' look like?," asks Clark. The videos of NASA testing various ceramics in the face of fast air speed gave some clues as to the colors and glows to prepare. "There's reference of the shuttle and Apollo missions re-entry."

The Tiangong station isn't built as a particularly strong structure and as people know space stations don't hold together when they re-enter. When pieces are ripped off the Tiangong, before they leave screen, they explode into many pieces which need to be created and modeled. They all are being super-heated along the way and showing ionisation effects of their own. There's a lot going on in every shot. Quite a few monumental management tasks.

Rising Sun Pictures had also to create views of the Earth which were a range of altitudes, from the point of re-entry, down through to the kind of height where the chute is deployed at 30,000 feet. There were a lot of public domain resources that the matte painting team used, but also there was a high-altitude balloon deployed to capture their own aerial shots. "We hired a group of engineering students from the university here in Adelaide," explains Clark. "Tim Horus Ballooning was supplied with a high-end prosumer camera and we gathered some incredible shots. As the balloon ascended, the payload is spinning around, so we set up the camera to shoot a five shot burst, and we stitched those shots together in a 12K panorama from about 45,000 feet. A lot of unique events happen as you look out along the horizon tangent. This gives you a really strong sense of what it's like at the edge of space." The Horus Ballooning project gave RSP thousands of images to use to help show what it was like to be at that required altitude.

Rising Sun looked back at some of the research during the production of Green Lantern, on atmospheric shaders, and brought that into the mix to replicate the light scattering model. "In that movie, we had a couple of fighter jets flying around at 60,000 feet and we had a lot of draw on computationally there," says Clark.

The Tiangong station was built at Framestore and the digital asset was sent across to RSP to finalise and use for the re-entry sequence. "They built the Tiangong model because they had to get Sandra Bullock into it," explains Clark. "Framestore built a full sized model of the Shenzhou re-entry capsule which they took to a lake outside of London and dropped into the water from a crane."


More imagery will be included as more are released by Warner Bros.