This operator simulates a simple cloud and sky reflection using anti-aliased noise. Unlike other reflective solutions, this one does not use a reflection model, thus avoiding the costs of ray-tracing.
This type of reflective shader was popular in the 1980's. Despite its obvious limitations, it remains useful today thanks to its speed and simplicity.
If the Surface Normal (
N) input is not connected, the global variable by
the same name will be used instead. Typically, you will not link
unless you want to displace the surface before performing the cloud
calculations. Bump Noise is one of many candidates for surface
displacement. If you do need
N itself, you will find it in the Global Variables operator.