CHAPTER ELEVEN: Rendering Passes and Compositing 359
Occlusion Passes
An occlusion pass is a close cousin of the shadow pass, only it represents
ambient occlusion instead of a shadow. Figure 11.25 shows an occlusion pass
for a complete scene.
[Figure 11.25]
An occlusion pass captures
the distance between each
of the surfaces in the scene.
In your composite, you can multiply occlusion passes with an entire scene,
or with a diffuse, specular, refl ection, or ambient pass. Figure 11.26 shows an
ambient pass of the scene before and after it is multiplied with the occlu-
sion. Multiplying an ambient pass with an occlusion pass can provide a ter-
rifi c replacement for very soft fi ll lighting, because the result resembles very
soft illumination with soft shadows.
[Figure 11.26]
An ambient pass (left) is
shown multiplied with the
occlusion pass (right).

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