The major plot point in The Prince of Persia is the “Dagger of Time” that can rewind time for the wielder up to two minutes, allowing them to change recent events.  While older studios may have simply rewound the film wheel to create the effect, that’s not sufficient for today’s discriminating audience.  Double Negative was called in to find a better way to do it, and wound up creating a a new technology called ‘event capture’ that combines photography, video, live action, CG, and a lot of math.

To accomplish this, multiple locked cameras were set roughly along the path of the final camera. “It’s sort of set up like bullet time,” said Ellis. Up to nine witness cameras were used, with each requiring the delivery of precise calibrations, lens, and set details. This was used to record the live action scene. Taking the resulting footage, Dneg roto’d out the character or characters, resulting in nine shots of roto per character which were intersected with each other in 3D, providing a cookie-cut of that person mapped on basic mesh which was accurate to the roto and camera positions with the real-world textures. The technique required a sharp image with little motion blur, but a maximum depth of field. Selection of the appropriate texture per frame was handled by transitioning from one of the nine cameras to the next.

via CGSociety – Prince of Persia.