Category: mental ray > Light
Shader Family: Light
Output: Color
This shader models physically correct light sources. Ideal for point lights, the light intensity falls off with the inverse
square of the distance. If physical correctness is not important, this falloff can be modified by changing the exponent. In
general the falloff is where is the falloff exponent and is the distance between the light source and the illuminated point. For directional lights there is no falloff since the
light rays are parallel.
The sphysical_light shader reads the direction, spread, and exponent parameters directly from the light source.
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The name of the shader node displayed in the render tree. Enter any name you like, or leave the default.
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Specifies the light energy. Since this shader is physically correct, its energy is distance-dependent and not normally in
the range 0...1. This is normally a copy of the light source energy, but keeping it separate makes it possible to adjust direct
and indirect illumination separately.
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If the shader is attached to a spot light source, this is the cosine of the opening angle of the inner solid cone.
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Optimization: if the illumination is less than the threshold, the illumination is discarded and no shadow rays are cast. The
default is 0 (zero).
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For flat area lights only (rectangle and disc): the default cosine illumination distribution is made more narrow by taking
cosine to the cos_exp power. The default is 1.
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