Maya 2012 Tutorial
How to Add Global Illumination with Maya Mental Ray
Global Illumination occurs around us every day. Whenever light strikes an object, the light changes color and bounces on to the next object. The new object is then lit with color from the previous object.
To see this in action, stand in front of the red wall on a bright sunny day. The sun strikes the red wall and anything the light bounces to turns red.
To accomplish this in Maya we must first activate Photons for the light and then turn on Global Illumination in the Render Settings.
Follow the steps in the topic, Adding Mental Ray Textures. You should have a sphere, floor and area light in your scene.
Select the light and in the Attribute Editor, Caustic and Global Illumination section, click Emit Photons.
Open the Render Settings panel by clicking the Render Settings icon.
Click the Indirect Lighting tab and open the Global Illumination section.
Click the Global Illumination checkbox.
Render your current scene and notice that the red from the floor projects onto the sphere.
If the Global Illumination is too intense, decrease the light's Photon Intensity setting in the Attribute Editor.
In the light's Caustic and Global Illumination section you can alter the Photon settings. The Photon Intensity value is similar to the standard light intensity slider.
Global Illum Photons controls the actual number of Photons released by the light.
Global Illumination Options
In the Render Settings, Indirect Lighting tab, Global Illumination section, you have access to Accuracy, Scale, Radius an Merge Distance settings.
Can't Find Mental Ray?
If Mental Ray doesn't appear in the Render Settings, Render Using: menu, choose Window > Settings/Preferences > Plug-in Manager. Make sure Mayatomr.bundle is loaded.