This operator takes two values for alpha based on the surface orientation relative to the camera and blends between the two with a rolloff as the bias control, effectively removing the silhouettes of the geometry edges.
It works well with a dent bump or with a displacement for generating smoke effects on particle systems.
Alpha Para determines the alpha value of the geometry that faces the
camera. "Para" stands for "parallel", which describes roughly how the
Surface Normal (
N) and the Direction From Eye To Surface (
I) are relative
to each other when the geometry faces the camera.
Alpha Perp determines the alpha value of the geometry silhouette, where
the Surface Normal (
N) is roughly perpendicular to the Direction From
Eye To Surface (
I) – hence Alpha "Perp".
Alpha Roll changes the mix of Alpha Para and Alpha Perp in a smooth, non-linear fashion.
If the Direction From Eye To Surface (
I) and Surface Normal (
are not connected, the global variables by the same names will be used
instead. Typically, you will not touch
N unless you had applied
additional displacement to the surface using an operator such as Bump Noise. If you do need to access the global variables directly, they are
available from the Global Variables operator.