Digital Lighting & Rendering, Second Edition

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).