It is also possible to change the behavior of different shaders by assigning their attributes to override sets.

In this tutorial, we will demonstrate how to add an Out Matte Opacity override to a set containing three different surface shaders applied to three separate spheres.

_{RGB surface shaders (left). Alpha channel (right).}

• Select the shader or shaders whose attributes you wish to modify and create a set for them.
• Select the set and open the Arnold section in the attribute editor.
• Then click on Add:

• Double click on outMatteOpacity to add it to the Arnold Override Attributes (ensure that the surfaceShader node is also associated with the set):

You should see that the Out Matte Opacity attribute has been added to the Extra Attributes of the Arnold set override.

• Change the Out Matte Opacity to black. Now, when you render, you will see the green sphere is utilizing the Out Matte Opacity attribute via Arnold's set override functionality:

_{Out Matte Opacity set to black}

_{Alpha Channel with Out Matte Opacity set override enabled}