Reverse Engineering 'Gravity'

Framestore's Tim Webber explains the unique workflow in Alfonso Cuaron's space adventure about floating in zero gravity.

Sandra Bullock, George Clooney and director Alfonso Cuaron on the set of Gravity. Click on any image to see a high-res version. All images (C) 2013 Warner Bros. Entertainment Inc.

Gravity marks yet another milestone in virtual production. It's this year's Life of Pi, only Sandra Bullock is lost in space with George Clooney as her tiger, so to speak. It's about adversity and rebirth and notably the first movie that realistically simulates the zero gravity experience of floating in space.

Alfonso Cuaron (Children of Men) spent nearly five years finding the right way to make Gravity as realistic as possible: an IMAX documentary gone bad. Working with cinematographer Emmanuel Lubezki and VFX supervisor Tim Webber of Framestore, Cuaron decided to make it almost entirely in CG (placing the actors' faces into the virtual environments with the only physical sets being the interiors of the two space capsules and portions of the ISS space station).

For that, though, they needed a process of reverse engineering in keeping with the photorealistic look and the director's penchant for long, continuous shots. They choreographed Gravity like an animated movie, beginning with complete previs by Framestore and The Third Floor (lighting as well as composition and camera movement), and then breaking the pieces apart and making them fit as needed. There would be very little cutting to cheat shots and the immersive experience was bolstered by Prime Focus' 3-D conversation (which began during previs).

"In some ways, it was doing things backwards and then forwards again," Webber explains. "So we had to finesse the animation to quite a large degree before we started shooting it. Having said that, we also had to factor in flexibility because you're working with actors, so when you have shots that go on for a minute and there are long dialogue passages, you need to make sure there is room for the actors to breathe. Certain sections required adapting live to how the performance was going."

Yet Lubezki needed a way of integrating live action and CG as well as real and virtual lighting to believably simulate zero gravity. He found his answer in the "Light Box," a 9-foot cube with panels comprised of thousands of LED lights. And they relied on Webber to make it work for scenes involving Bullock. They were assisted by the Alexa mounted on computer-controlled devices with robot arms and a special wire rig for tilting and rotating Bullock.

"It gave us huge flexibility with the LED lighting," Webber observes. "To spin it around the character was hard enough, but it also had to change color and required detail in the light to get the right surface texture, to get the right lighting on her face. When Sandra's supposed to be isolated in space, and she finds herself isolated in this box, it worked quite well. And when she's spinning away and shut in this box and can see a massive picture of the Earth on the walls, it gave her a guide for what was going on around her."

Outside the box, Bullock and Clooney were both manipulated like marionettes by a unique 12-wire rig manned by a puppeteer for more extreme angles.

Gravity additionally required a totally different mindset from the animators, who were used to dealing with weight. "We retrained them about what goes on in space and they had to break their habit of animating in certain ways," Webber continues. "It was unnatural at first. We also used some simulation and other tricks just to see what would happen if someone got thrown against the space ship and bounced off or if someone's being tugged along by someone else with their safety tether. You would discover unexpected results and that provided good ideas for bouncing around and how hard it was for George to control Sandra by his tether."

The animation also had to be extraordinarily detailed, and they had plenty of NASA reference footage and images for reference. Not only were the space ships and the universe a challenge, but also little details such as when Bullock fixes the electronics on the Hubble telescope: turning knobs and pushing circuit boards in and the subtlety required in the gloves.

Meanwhile, the debris storm was also daunting, simulated in Maya. "What's difficult about that is you have to simulate the debris and the damage it does, and you have to animate the character and you're trying to marry those two bits of motion in a way that's interesting and dramatic and then you've got to get the camera to move within all of this," Webber conveys. "And you've got to do it again without the use of cuts to cheat.

"Because of these long, exploratory shots where you see stuff in the wide shot and then you go into the close-up and then you see it from the other way around, everything has to be choreographed to make sense and to be continuous."

This marked the first time that Framestore used Arnold for rendering. It was a big leap forward to go down that physically-based route, according to Webber. "To get it finished we had to develop a lot of extra code: 71,000 lines of shader code were written for Arnold to make it work and to get the surface qualities of all the different materials and fabrics have to hold up during these long shots."

Webber also helped plot the orbital path so that it was plausible as well as beautiful. The Earth was a mixture of techniques: renders that are based on atmospheric light scatter but Framestore also used matte painting with finely detailed surface textures.

"We mixed it up with lighting and interesting geographic landscapes," Webber suggests. "At one moment, you'd be over a nice, cool ocean; then you'd go from the warm deserts to the city lights of Europe at night to a lightning storm."

The star fields originally had 200,000 stars and were based on how real stars are laid out in the sky. But it wasn't enough so they added 2 million smaller, dimmer stars to fill it out. The camera's going everywhere so you have to fill the whole 360-degree view.

Even after they were done, however, Cuaron decided to change the opening 13-minute shot (the longest in the movie) by turning the space shuttle upside down. "Quite often it's helpful in visual effects to flip shots around so you can examine them with a fresh eye and spot errors. Alfonso looked at the space shuttle upside down and realized it was a better position. It took two months of tweaking because nothing is simple with such a long shot. They had to slightly re-animate and then completely re-render a long section as it turns the right way up because it goes through a spin. And some extra modeling went into revealing more clearly other parts of the shuttle and Hubble that had not been seen close-up. And that it joined back into the shot with the stereo cameras.

"It was worth the extra work, Webber insists. That meticulous care helps elevate Gravity above other space adventures. "It gave you a better view of the Earth and it was more disconcerting seeing it upside down and then right side up."

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Bill Desowitz is former senior editor of AWN and VFXWorld and the owner of Immersed in Movies (www.billdesowitz.com). He's also a columnist for Thompson on Hollywood at Indiewire and contributing editor of Animation Scoop at Indiewire. Desowitz is additionally the author of James Bond Unmasked (www.jamesbondunmasked.com), which chronicles the 50-year evolution of 007 on screen, featuring interviews with all six actors.

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