127 Hours is the true story of mountain climber Aron Ralston’s remarkable adventure to save himself after a fallen boulder crashes on his arm and traps him in an isolated canyon in Canyonlands National Park, Utah. Directed, Co-produced and co-written by Danny Boyle, the film stars James Franco as Ralston. The film received near universal critical acclaim, including a Best Actor award for Franco from the New York Film Critics Online. Tribute of a different sort has been paid by the many reported faintings that have occurred during the film’s graphic – though unsensationalised – amputation scene.

With a $18m budget, 127 Hours was a very modestly scaled project by Hollywood’s standards. VFX were essential, but they would have to be utterly invisible, seamlessly integrated into a gripping human drama. Boyle turned to London-based Union for the work. The team delivered 350 shots encompassing complete CG environments, dust and fluid simulations, CG horses, set extensions, limb removals, prosthetic enhancements and complex rig removals.

VFX Supervisor and Co-Founder of Union, Adam Gascoyne was involved right from the start and attended the nine week shoot on location in the Canyonlands National Park and at the Salt Lake City sound stage where a replica of the crucial canyon was built. The replica was 60ft long and 30ft high, which meant that a significant amount of set extensions would be required. Says Gascoyne, “We used a LIDAR scan of the set, cleaned it up, textured it in Maya and then did the set extensions in Nuke. Matters were complicated by the fact that there was no room for a green screen above the canyon set. Because of its shape the lighting rigs had to go directly above it, and the only way of lighting it evenly was to use white silks, so we had silks as opposed to green screens, which was…interesting. As was getting the LIDAR gear into the real location, but we managed.

“We contributed around 50 shots to the amputation sequence itself,” continues Gascoyne, “We projected textures onto basic models inside Nuke and with a little bit of help from Maya and quite a lot of compositing help we managed to achieve some excellent results. We worked closely with the physical effects make-up guys, who’d built a prosthetic arm that was used on set. Our job was to come in and help when needed. Basically this entailed blood addition, tidying up the edges of the silicon, and adding more connective tissue. Also, maintaining the look and keeping it completely consistent throughout the sequence was vital.”

Union were a perfect fit for Boyle’s production and methods of working. “Danny likes to pop in several times a week,” reveals Tim Caplan (VFX Producer and Co-Founder), “He is very hands on and likes to give direct feedback to the artists, which is easy to do with a company like ours.”