Light parameters are message attributes. Connect any output attribute of a light node (not the shape node) to, for example, the desired element of a light array of your custom material shader.

These extensions should enable you to create pretty much any shading network supported by mental ray. It can be either exported to a file or rendered from within Maya. Some restrictions apply:

• Cooperation between proprietary mental ray shaders and the Maya base shader library is not always seamlessly possible. Although much work has been put into making the Maya base shaders compatible with standard mental ray shaders, some restrictions still apply. Custom shaders might thus have to be designed in a special way, if cooperation between the Maya base shader library and custom shaders is desired.
• The mental ray Phenomenizer represents a shader declaration, not a definition. Therefore, it cannot be directly linked into a shading network.