Edinburgh Napier University

As Head of Disney UK Research in the last decade, Professor Mitchell helped to spearhead the company’s push on interactive digital technology during a time of what he describes as an ‘industrial revolution’ of computerised imagery techniques, which fed into billion-pound grossing films such as Finding Dory and Pirates of the Caribbean 5.

Hired by Disney initially to work on videogames such as Split Second and Disney Infinity, Professor Mitchell suggested to the corporation that they could begin patenting many of the visual technologies that were being developed for Disney Interactive. He remembers:

Technology breakthroughs

He began to lead the company’s research for interactive graphics across all Disney businesses, setting up a Disney Lab in Edinburgh to employ local talent which soon attracted researchers from around the globe. Funding from InnovateUK allowed Prof Mitchell and his partners in the industry to come up with several breakthroughs in technology, which proved essential to Disney’s film operations.

He explains:

"And to be first with techniques enabling that is incredibly valuable in such a highly competitive field.”

Among Professor Mitchell’s innovations is technology that captures actors’ performances live on set, for use in CGI animations. Previously, performance capture for CGI had to be done separately and added in digital postproduction to acted scenes. Professor Mitchell’s techniques use far fewer sensors for action capture, so acting wasn’t impeded, with the sensor data fed into a physics-based algorithm that computes a physically plausible position and motion for the character.

His team assisted on Star Wars: Rogue One production which included one of the first complete digital resurrections on film. The character Grand Moff Tarkin – not seen since the 1977 original - was needed for key scenes, but actor Peter Cushing had since passed away. Professor Mitchell remembers: “We assisted the capture of an amazing actor’s performances [Guy Henry] using photographic reconstruction methods, and the Industrial Light and Magic Visual Effects team were able to remap that with archival processed footage of Peter Cushing.”

Improving image quality and production speed

‘Denoising’ is another of Professor Mitchell’s research techniques that has substantially contributed to the success of films such as Finding Dory, which made over $1bn at the box office. Problematic discolouration - or ‘noise’ - can arise from the light samples that go into making each pixel used in these films. He and his team established new methods to improve the rendering of high-quality images from 3-D models, which drastically reduces erratic colouring and preserves fine detail, whilst cutting an average 8 hours of render processing down to just a few minutes.

The highest image quality movie visual effects typically take many hours to render each of thousands of frames, at significant costs. Working with Edinburgh Napier colleague Dr Babis Koniaris, Professor Mitchell has also helped to solve this problem by processing renders into a flexible light field video format able to provide animated immersive views over 120 times a second.

Reducing the gap between the digital and physical

These techniques have the potential to save film makers time. For example, a crucial scene for “Pirates of the Caribbean 5: Dead Men Tell No Tales” had been shot on location at dusk but incorrectly filmed. Professor Mitchell’s techniques allowed the relevant section to be ‘cleaned up’ digitally in post-production, providing the director an option to use the processed footage and avoid a reshoot.

Professor Mitchell is now the Technical Director of Rendering for games giant Roblox Corporation and assisting two UK companies as CTO, where he is continuing his work in digital innovation. He muses:

"It’s challenging to figure out how to make everything happen computationally within fractions of a second. Real-time rendering reduces the gap between the digital and the physical, and this is what’s always excited me most."