2008

On the left is an atmosphere element, in this example, a light fog on the back side of
the fountain.
On the right is the Z-depth. The fog uses the depth of the image and objects to
determine its density. The Z-depth element contains these depth values.
Compositing Rendered Elements
In general, you can composite elements using additive composition, which
is independent of the compositing order.
The main exceptions are the background element, atmospheres, and shadows.
■ Background: The background is not trimmed against geometry, the
background should be composited under the other elements.
■ Atmosphere: The atmosphere element should be composited over all other
elements.
■ Black-and-white shadows: Black-and-white shadows should be composited
over the rest of the image (aside from the atmosphere), to dim color in the
shadowed areas. This technique does not take colored lighting into account.
In other words, the layers when you composite using black-and-white shadows
appear like this:
Top: Atmosphere
Second from top: Shadow element
Middle: Diffuse + Specular + ... (other elements)
Bottom: Background
6150 | Chapter 18 Rendering