Help with a Shader
A quick (or not so quick) question: Is there any way to access the level of illumination using a shader? I realize that Shadow Glow (in the DCG's Shaders Plus collection) turns the Glow channel on or off depending on the lighting, but it only works on the glow channel of its subshader. Is there a more general way to produce a grey scale indicating how much light is falling on a given point? For example, to use in a mixer or color gradient?
Hopefully there will be an easy/obvious answer... *crosses fingers*