Graphics Reference
In-Depth Information
1.
2.
Reflectance function
Diffuse
component
Diffuse
reflectance
function
Light
Reflectance
function
Specular
component
Specular
reflectance
function
3.
4.
Specular (
u
,
v
) map
Reflectance function
Diffuse (
u
,
v
) map
Viewpoint
1
Viewpoint
2
Viewing direction
Viewpoint
N
Figure 8.34
Steps in capturing face reflectance fields for
Spider Man 2
using a light stage.
(The normal direction is practically constant using any of the reflectance
functions captured from different viewing directions).
3. The reflectance functions are densely resampled over the sphere of viewing
directions; this simplifies the process of reflectance map lookup in varying
surface direction.
4. The face is rendered using the reflectance maps and the environment map
for the particular scene and animation frame. The diffuse and specular re-
flection extracted from the reflectance functions for pixels across the facial
surface are stored in a
texture map for the face, which is referenced
in computing the lighting using the environment map for the incident light.
(
u
,
v
)
A major challenge in the production of the movie was the efficient acquisition
of the face reflectance fields—the actors' faces could not be recaptured with every
