How is a MIRROR Without a Coating Handled?
Authored By: Mark Nicholson
How is a MIRROR Without a Coating Handled?
This article is also available in Japanese.
Question: I have a MIRROR surface or object, but I have not defined a coating for it. How is its reflectivity accounted for?
Answer: If a surface or object has the material type MIRROR, and no coating is specified, then the surface is assumed to be coated with a thick layer of aluminum, with an index of refraction 0.7 - 7.0i. The aluminum layer is assumed to be thick enough that no light propagates past the layer.
This means that an uncoated mirror surface has a reflectivity of less than 1, just as an uncoated refractive surface has a transmission of less than 1.