Among the many dreamscapes in Christopher Nolan's new sci-fi flick "Inception," one of the most memorable is the image of a chic modern hotel that defies the rules of gravity. At one point, Joseph Gordon-Levitt's Arthur careens down hallways that shift and turn upside down; at another, he fights an array of armed men in zero-gravity rooms, bouncing off walls and ceilings like a martial-artist-cum-astronaut. Comparisons to "The Matrix" are inevitable, but what makes these sequences unique is that few computer effects were used.

"There's...