Category: mental ray > Photon Volume
Shader Family: Photon Volume
Output: Color
This is the volume photon shader that matches parti_volume. It shares the same parameters (refer to this shader for all parameter descriptions).
The and options are handled somewhat differently for the parti_volume_photon shader and are discussed further in the table below.
The options for and are ignored since there is no direct illumination in the photon shader.
All other parameters, especially , need to be identical to the parameter settings in parti_volume in order to preserve consistency in the algorithm.
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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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The color of the scattering medium. This determines the color of the indirect light that is scattered by the medium. It also
acts as a multiplier of the photon energy for the photons in the photon volume map.
Note that in mental ray there are three data structures where photons can be stored: the GI, the caustics and the volume photon
photon map. The first two can be independently color corrected.
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The minimum refraction level at which photons are stored. This is handled differently for caustic and GI photons. For GI photons the maximum level is set with the global option photon_refraction_depth. Caustics photons storage is very different. It depends on more variables. First, the global option photon autovolume can be
set or not. If it is not set then caustic photons are only stored after at least one refraction or reflection. If it is set,
and the light source is inside the volume then caustic photons can be stored. If the light source is outside the volume, then
caustic photons are only stored after at least one refraction or reflection.
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