In order to compute volume caustics and global illumination in participating media, the media need volume photon shaders. A volume photon shader will usually have the same name as the corresponding volume shader, but with " _photon" appended. Details on photon tracing in volumes can be found in the mental ray manual.
The volume photon shader that matches parti_volume. It has the same parameters.
color "parti_volume_photon" ( integer "mode", color "scatter", scalar "extinction", scalar "r", scalar "g1", scalar "g2", scalar "height", scalar "nonuniform", scalar "min_step_len", scalar "max_step_len", scalar "light_dist", integer "min_level", boolean "no_globil_where_direct", array light "lights")
All other parameters, especially extinction, need to be identical to the parameters of parti_volume, this to preserve consistency in the algorithm.
Deprecated transmat_photon is the material photon shader that matches transmat, used for an enclosing surface of a participating medium or volume that is not a mental ray hull object. It simply continues to trace the incoming photon in the same direction without any interaction with the current object. Such a volume container should be invisible to photons itself.
color "transmat_photon" ()
There are no parameters.
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