specular-color computes the base color of conductors based on spectral data.
The base color is output in linear and sRGB formats. The base color is the reflectance
at normal incidence (0°) and is often noted f0.
specular-color can also compute the perceived color of a conductor at another angle,
set to ~82° by default. This value is particularly useful when used in combination with
the Lazanyi-Schlick model to better approximate the behavior of metallic surfaces at
grazing angles. See Hoffman 2019, "Fresnel Equations Considered Harmful".
specular-color <spectral data file>The spectral data files can be obtained from Refractive Index.
For instance, to compute the base color of gold:
specular-color data/gold.txtTo set the second angle, use -a to specify the angle in degrees:
specular-color -a 75 data/gold.txt