Like many action sequences, the Chunnel scenes in “Mission: Impossible” began as animatics — that is, pre-visualized mini-movies that use drawings and sometimes models to work out the pacing and music placement in a scene. John Knoll used CGI he learned to develop for “Star Trek: Generations” to make the animatics for “Impossible.” The shots were then carefully laid out on a storyboard to let the filmmakers know what and how to film things. Joe Letteri, the film’s associate VFX supervisor, described the process thus:
“[W]e have storyboards of the whole sequence to help us understand what we’re doing. These evolve from simple animatics to help the director visualize the action to more sophisticated storyboards that were done once we started getting more of the details in place. It helps us to maintain our continuity and to make sure that the story’s progressing as it needs to. This train is traveling at speeds upwards of 200 miles per hour with Tom Cruise on top of the train.”
Despite the overwhelming volume of action films in the world, there are really only so many ways one can shoot a chase scene. Letteri sensed that some originality would be needed, and that was where the director came in. One can throw helicopters at trains in tunnels all day, but it still needed to be personally directed by a knowing director in order to be interesting. The FX team showed off their toolboxes, and Brian De Palma could extract what he needed. Letteri explained:
“People have seen helicopters before, and they’ve seen tunnels before, but what we’re giving Brian the ability to do here is to tell the story the way he wants to. We’re giving him the ability to create an action that has never been possible.”