parti_volume

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 scatter and min_level options are handled somewhat differently for the parti_volume_photon shader and are discussed further in the table below.

The options for light_dist, no_globil_where_direct and lights are ignored since there is no direct illumination in the photon shader.

All other parameters, especially extinction, need to be identical to the parameter settings in parti_volume in order to preserve consistency in the algorithm.

Name

The name of the shader node displayed in the render tree. Enter any name you like, or leave the default.

scatter

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.

min_level

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.