Scene Requirements
In order to work correctly with the misss_physical
shader, it is necessary to set up the scene following these
requirements:
- Version: this shader will not work with version of mental ray
prior to 3.3.
- Link/include: link the subsurface shader library and include
the subsurface.mi shader declaration file in the .rayrc file, or in
the scene file itself, if this is not handled automatically by the
modeling package that mental ray is built into.
- Raytracing must be activated.
- Caustics and/or global illumination must be enabled. (Caustics
only is preferred to global illumination only.)
- A light, preferably focused on the subsurface-scattering media
object must specify an energy value as well as emit caustic and/or
globillum photons.
- The misss_physical
shader must be used both as a material and a photon shader, or the
material Phenomenon must be used. It must have a light that emits
photons in its lightlist.
- Subsurface-scattering objects or their instances must be
flagged as receiving and casting caustics and/or global
illumination.
The following .mi scene fragments ensure that the conditions are
met:
- At the beginning of the scene file:
min version "3.3.0.7"
link "subsurface.so"
$include "subsurface.mi"
- In the options block:
trace on
caustic on
globillum on
- In the light definition (example):
energy 10000 10000 10000
caustic photons 250000
globillum photons 250000
- The shader and material definition:
shader "myshader" "misss_physical" ("lights" [ "lightinstancename" ])
material options
material "materialinstancename"
= "myshader"
photon = "myshader"
end material
- In the object or its instance definition:
caustic 3
globillum 3
The shader provides useful feedback when executed, using info
messages. In any case verbosity level 5 is suggested to debug your
scene. The shader statistics reports are especially valuable to
estimate correct values for the following parameters:
- depth: look for information in "channel 0 1 2" and "photon
statistics".
- max_radius and max_photons. Look for information in
"multi-scatter photon per samples statistics".
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