Big Hero 6 uses a custom-built piece of software called Hyperion, its sole purpose is to calculate the way light reacts off different objects on its way to the 'camera'.
It can calculate in real-time the way it would pass through a glass of water if the audience were staring at it, or the way it would pick up colours as it passes through a stained glass window.
That may not sound like much but when you consider that the film's main location features over 83,000 separately created buildings you should start to get an idea of the scale.
Another way of looking at it is that as the film's director reported to Engadget, the software Hyperion "could render Tangled from scratch every 10 days."
In total the film became such an undertaking that the team quickly realised that humans physically wouldn't be able to cope, so they built automated systems which would self-maintain the supercomputers with any problems being sent through to the team as alerts on their iPhones.
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