Apple Shake 4 - Manual (Page 968)

968 Chapter 32 The Cookbook
Keying Tips
This section covers keying techniques.
Keying Clouds
This script can be found in doc/html/cook/scripts/clouds.shk. The images used are the
moon.iff and sky.iff files found in the
Tutorial_Media directory.
This is one potential technique for keying clouds, but may also be useful for flames. It
discusses several approaches.This script puts the moon behind the clouds:
You might think a color-based key would work, but in this image nearly everything is a
shade of blue, so that won’t work the way you want.
Another tactic would be to use a LumaKey node. In this attempt, the moon is corrected
(using a Compress node, an Other–AddShadow node to add the white glow, and then
positioned with a Move2D node) to adjust the color and position of the moon. A key is
pulled on the clouds with LumaKey, and a Layer–Atop is used to layer the moon only
where there is alpha in the background. This displays two typical problems with this
sort of keying—there’s a black edge, and there is not complete opacity in the thick part
of the clouds. This is not what you want.