Using Light Lists

Certain types of shaders such as surface materials, textures, and volume shaders, allow you to create arrays of lights called light lists. These light lists let you specify which lights in the scene will contribute illumination to the shader's effect. Many of the shaders in the mental ray category make use of light lists.

Essentially, the list list associates lights to a material. The material then applies the illumination from these lights to the shaded surface of the object to which it is applied (if the material is shared, all objects that share it are illuminated by the lights in the light list).

When the light list is not used, the light-object relationship is no longer driven by the material, instead lights can be associated to objects in your scene using the selective light property. If an object has no specific light associations, then it is illuminated by all of the lights in your scene (which is the default behavior). For more information, see Using Selective Lights.

Add	Adds an empty entry named Item to the light list. To fill the Item with a reference to a light in your scene, click the Pick button.
Clear	Removes all Item entries from the light list.
Item	An entry representing a single light in the lights list.
Pick	Allows you to choose a light in your scene that will be used to compute the effect. Click the Pick button. In the pop-up explorer, select the light you want to use. Right-click outside the explorer to end the picking session. The Item text box displays the name of the selected light.
	Click the Edit Array Item icon (the " blue socket") to open a pop-up menu with the following commands: Remove: Deletes the light item from the light list. Once a light is removed from the list, it no longer influences the effect. Move Up/Move Down: Promotes or demotes the light item in the light list. The position of a light item in the light list indicates its order of evalution. Changing the evaluation order can impact the results of the final effect.

Setting the Light List Mode

The light list mode controls how the lights defined in the light list are used for illumination. The modes are as follows:

Use Light List: Enables the light list. In this case, the illumination is done using all the lights in the light list.
Inclusive Light List: Enables the light list in inclusive mode. In this case, the illumination would also be evaluated for all lights in a group.

Note that currently, Softimage does not push light groups to mental ray and, therefore, the Inclusive Light List mode behaves the same as the Use Light List mode.
Exclusive Light List: Enables the light list in exclusive mode. In this case, all lights except the ones specified in the light list are used for illumination.
Ignore Light List: Disables the light list. In this case, objects are illuminated by their associated lights (if defined), otherwise all of the lights in the scene are used.

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