Defining global illumination using irradiance particles in a scene is faster and more straightforward than applying traditional global illumination. All of the objects in a scene participate in irradiance particle calculations, so you do not need to concern yourself with setting up casters and receivers.
The following is an overview of the process of setting up irradiance particles. The irradiance particles options listed below and others that are not discussed in this section are all described on the Irradiance Particles tab of the mental ray Render Options Property Editor [Properties Reference].
To create an irradiance particles effect
Make sure that your scene contains at least one light source. Use a physically accurate light with an appropriate intensity setting.
Set the mental ray options for the pass (or render region) that you want to render with irradiance particles.
On the Photon Global tab, select Irradiance Particles / Final Gather as the Indirect Illumination Algorithm.
On the Irradiance Particles tab, select the Enable checkbox to activate irradiance particles.
Irradiance particles are preprocessed and rendered when you render your scene or draw a render region.
On the Photon Global tab, the Importons options are now available for editing. For the most part the default settings provide satisfactory results, but you can tweak them if you need to further optimize the effect. See Storing Irradiance with Importons.
Return to the Irradiance Particles tab and adjust the Accuracy and Interpolation values. These are the main settings that will help you achieve quality and good rendering times. See Setting Accuracy and Interpolation for Irradiance Particles.
Set the Environment options if you want your environment shader to contribute towards the irradiance calculations, see Storing Indirect Light from the Environment.
Set the Particle Map File options to use the map and specify its behavior. See Using the Irradiance Particle Map.
