reflectlight VEX function
Computes the amount of reflected light which hits the surface.

vector reflectlight(float bias, float max_contrib)

vector reflectlight(vector P, vector D, float bias, float max_contrib)

vector reflectlight(vector P, vector N, vector I, float bias, float max_contrib)
Computes the amount of reflected light which hits the surface.
bias is typically a small number (for example 0.005) used to help eliminate selfreflection.
max_contrib tells the renderer how much the reflected light will contribute to the final color of the pixel. This is typically the maximum of the reflection component of a lighting model. This has no effect on the resultant color. This value should typically be less than 1.
There are also two “general” forms of reflectlight which take a position (P) and direction (D). There is also a form which takes a position, direction and incident ray (I) and computes the reflection vector.
See optional shading and image filter parameters.
surface mirror(vector refl_color=1; float bias=.005) { Cf = refl_color * reflectlight(bias, max(refl_color)); }