Location:
The Render Manager > mental ray (Global Renderer)
The Render Manager > (select a pass) > mental ray
Set a current pass and choose Render > Render > Renderer Options from the Render toolbar.
Tab: Irradiance Particles
Options: Particle Map File [Properties Reference]
Irradiance particles are also able to gather light information from the environment shaders that simulate a global environment for the reflective objects in your scene. For more information about environment mapping, see Using Environment Map Shaders [Texturing].
Select the Enable checkbox if you want to gather light from the environment shaders in your scene.
Set a scale factor for the Intensity of the effect.
Specify the number of Rays used to evaluate the irradiance coming from the environment shader. Here are a few guidelines:
For outdoor scenes, the Environment Rays should be set to the same number as the Accuracy Rays (which are discussed in Setting the Number of Rays).
For indoor scenes, where the environment is only seen through a small window, it is better to increase the Environment Rays value above that of the Accuracy Rays value.
When possible, a better solution is to turn the Environment option off and use the Portal Light (mia) shader instead.
