'Avatar' digs deep for interactivity on iTunes.

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Given "Avatar's" technological achievements, it's no surprise 20th Century Fox is turning to James Cameron's sci-fi blockbuster to break new digital ground with the film's release on Apple's iTunes.

Starting Tuesday, the film will be available in HD--the first in the format for Fox on iTunes--and offer interactive extras that will enable viewers to deconstruct 17 scenes in splitscreen that reveal how the f/x for the sequences were created.

As a scene plays, the screen is broken up to simultaneously show various f/x layers. Another feature lets users move a cursor across the screen to reveal what part of a scene was greenscreen on set. …