Beginning Maya 2008, mental ray for Maya uses native mental ray light linking. Shaders are no longer responsible for their own light linking. All the Maya linking information is automatically handled by the mental ray core and shaders automatically receive the relevant light information.
All of the mental ray shaders provided with Maya have been set to automatically work with this new feature. The light linking mode has been preset for you.
This feature also simplifies your workflow for integrating custom mental ray shaders. Previously, to make use of Maya light linking, shaders would have required special purpose code. This code can now be safely removed. Refer to the examples and readme.txt in Maya2012/devkit/mentalray/docs/writingShaders for more information.
If you have a scene created using Maya 8.5 or any earlier version of Maya, you may need to re-export your .mi files to mental ray.
All mental ray shaders have a choice of 4 light linking modes. You can set this mode under the Light Linking section of the mental ray shader node.
Illumination using the lights parameter. If no lights are specified, then the instance light list is used. If no instance light list is specified, then all lights in the scene are used.
Illumination using the specified lights in inclusive mode, In other words, instances of groups of light instances are evaluated to all light instances in the group.
Illumination using the specified lights in exclusive modes, in other words, using all lights except for the specified ones.
Use the instance light list. If no instance light list is specified, then all light instances in the scene are used. This is the default.
