Graphics Reference
In-Depth Information
5.3.3 IBR in Movies
As previously mentioned, an notable early use of image-based rendering in movie
production was in the “Bullet Time Shots” scene in the movie
The Matrix
[Wa-
chowski and Wachowski 99]. George Borshukov, who was in charge of technical
design in
The Matrix
, earned his PhD degree in computer science at the Uni-
versity of California, Berkeley. He became familiar with image-based rendering
through his involvement with the production of Debevec's short film
The Cam-
panile Movie
. In the “Bullet Time Shots” scene of
The Matrix
the camera swings
around the main character 360 degrees while the character moves in extreme slow
motion. The character was not created with CG; photographs were captured by
cameras placed in a circle around a live actor. The cameras were set to capture the
images in sequence around the circle, with a slight time delay between adjacent
cameras in order to capture the motion of the actor. Assigning each sequential
image to a frame in the animation creates the appearance of a camera sweep-
ing around a slowly moving character. Image-based rendering was then used to
create in-between frames for the appearance of smoothness. The objects in the
background were recovered separately, as it was difficult to capture the back-
ground using the circular camera arrangement.
IBR had been used in the entertainment industry prior to
The Matrix
.The
1995 music video
Like a Rolling Stone
[Gondry 95], directed by Michel Gondry,
shows characters frozen in midair produced using IBR (
Figure 5.14
)
. It is said
that this music video provided inspiration for the “Bullet Time Shots” scene in
The Matrix
. The visual effects for the
Like a Rolling Stone
video were handled
by the French/American digital effects company BUF Compangie. Researchers
at BUF had been developing tools for stereophotogrammetry since the 1980s,
even before IBR was actively studied in mainstream computer graphics. These
tools were developed to reconstruct a 3D model of an object from a collection of
photographs captured from different viewpoints. The captured photographs were
also used to create the texture to be mapped onto the reconstructed 3D model in
the rendering process. This work represented an early version of image-based
modeling and rendering.
During a visit to BUF Compagnie in France, Michel Gondry became inter-
ested in how the IBR tools under development there could be used in actual film
production. Gondry wanted to create a scene where a camera whizzes through a
room filled with people frozen in mid-motion. The engineers at BUF did a test
with Gondry himself as the subject. Using two synchronized still cameras, they
captured a pair of photographs where he was jumping in the air surrounded by
buildings. Then they demonstrated that, once the 3D environment was recon-
structed, it became possible to create a scene where a virtual computer camera
