While the story and logic of the script for 'Inception' have taken some flak, one thing everybody agrees on is that the visuals are arresting.
Wired talks with the film's visual effects supervisor, Paul Franklin (Batman Begins, two of the Harry Potter movies, The Dark Knight).
(...)For something like the Paris-folding sequence the script basically said, “Ariadne [played by Ellen Page] looks down the street as it folds in on itself, forming a giant cube universe.” It reads as a great description, but it doesn’t explain the process of how the elements transition into the end result. So, in designing these effects we had to address a lot of the outlying questions: How does the lighting change? What happens to the people walking and driving on the road? Should it fold as if on a hinge?
These decisions started as conversations describing different ideas, and then we went through the process of having artists producing concept sketches. From there, we created rough computer animations [called previsualization] to give us a working idea of what this one line of script would look like in motion. It’s a very fast, interactive process.