No other single event has been so extensively visually documented, therefore the onus was on Double Negative to make sure that their recreation of the Lower Manhattan area and the destruction was completely accurate.
The endless coverage of the disaster was a double-edged sword, as Double Negative’s Visual Effects Supervisor, Mike Ellis, pointed out, “It was a bonus to have all the footage to refer to, but on the other hand it meant that there was absolutely no room for error”.
Double Negative’s work covered two main stages; pre-collapse & aftermath which meant building the towers and complex, many of the buildings around them and the surrounding streets, then adding dynamic effects such as smoke, burning, falling paper and debris. The second stage was post-collapse which involved building Ground Zero in CG along with all the rubble, smoke and dust.
Double Negative also produced a large number of ‘invisible effects’ shots for the film.