bullet time

The Matrix DVD contains an extensive interview with John Gaeta, the visual effects director for Manex, about how the film's bullet time sequences are composed. The movie's Web site at www.whatisthematrix.com contains a shorter synopsis. A brief walkthrough of the process:

1. The entire shot is "sketched" using 3D modeling software, describing who is going to be in what position when the camera is in a certain spot.

2. The "bullet time" room is set up with bright green walls, floors, and ceiling, while a series of identical digital cameras are positioned in holes behind movable bright green panels. Computer-guided lasers are used to place each camera as precisely as possible, based on the computer-generated "sketch". High-speed full-motion cameras may be placed at either end of the sequence.

3. The actor or actors are rigged up with wires, if necessary, in the center of the room. The cameras are all fired in sequence by a single computer, coordinated down to the millisecond. The entire take lasts for only a couple of seconds in real time, if that.

4. Now, the post-production begins. First, the wires are removed digitally.

5. Since the digital cameras can only be spaced so close together, computer software is used to interpolate the missing frames to produce a smooth effect.

6. 3D modeling software is used to create a virtual background for the shot, based on photos of the actual room. The "sketch" is used to move a virtual camera around this room to exactly match the positions of the digital cameras.

7. The background and actors are composited together, frame by frame, to produce the complete shot.

End result: a few hundred man-hours and computer hours to produce between three and fifteen seconds of eye candy. Of course, it falls to the director to make sure they were hours well-spent; special effects are only as good as the story around it.

Bullet Time is used to capture part of a movie in slow motion, however it differs from slow motion as the end result gives the effect that the dynamic camera movements occur in 'real-time' whereas only the on-screen action is slowed down (or paused all together).

The goal of Bullet Time is essentially the same goal of slow-motion, to allow viewers to better interpret the smaller/faster elements of an action scene. Bullet Time works better than slow motion in cases as it allows the camera to be moved while the slow-motion action takes place. As an example, in the movie 'The Matrix' the rooftop scene where Neo dodges a volley of bullets from an Agent's Desert Eagle is easy to comprehend because of the action running at around 30 times slower than real-time. If you now imagine this scene played through at full speed, you would miss the fine detail in the scene because the bullets, already very small, move way too fast to be captured on camera or for us to see. As a result it would look like Neo is just falling over, and quite frankly wouldnt be worth putting in the movie.

Bullet Time, apart from having been used in 'The Matrix', now appears in computer games. The PC CDROM title 'Max Payne' allows players to trigger at will the Bullet Time effect so they too can easier interpret the action around them. Many believe this one effect, ripped from 'The Matrix' was responsible for the game becoming such a hit.

Basically it's just a tag on the box. Anyone can still use slow motion and technology similar to Bullet Time. They just can't call it Bullet Time.