Maya 2012 Tutorial
How to Enable Final Gathering with Maya Mental Ray
Final Gathering is a Mental Ray rendering technique that emulates the way light works in the real world.. 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 can use Global Illumination and/or Final Gathering.
Follow the steps in the topic, Adding Mental Ray Textures. You should have a sphere, floor and an area light in your scene.
Render your scene by clicking the Render Current Frame icon. Notice how the sphere is dark on the bottom and not illuminated by the red floor.
Open the Render Settings panel by clicking the Render Settings icon.
Click the Features tab and click the Final Gathering checkbox.
Render your current scene and notice that the red from the floor now casts onto the sphere. The additional realism does come with price in additional rendering time.
Lighting with Shaders
In this example we lit the scene with an area light. You can also light your scene by adding an object and assigning the object a Surface Shader. Change the Surface Shader Out Color and the object illuminates the scene when Final Gathering is used.
To see an example of this type of lighting, see topic, Object Lights with Mental Ray.
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.
More Final Gathering Settings
To access the Final Gathering settings, click the Indirect Lighting tab, Final Gathering section. The sliders and parameters can be tweaked to fine tune your lighting.