I am using maya 2016 and arnold 4. When I create a custom AOV it is empty. No objects are rendered. there is nothing in the alpha either? What am I doing wrong in creating the custom AOV?

[Stephen.Blair]

What are you doing? If you just create a custom AOV and don't set up anything to write to that AOV, it will be blank.

[Anonymous]

Thanks Stephen, I guess that is the part I can't seem to figure out. How do I write an object to that AOV? I ultimately want to work with lightobjects (like 'light selects' in vray). Like this tutorial: https://ddankhaziportfolio.wordpress.com/2017/04/26/light-groups-in-arnold-5/

[Stephen.Blair]

For that, you need to move to Arnold 5

In general, you can either assign a default shader to a custom AOV, or you use the aov write color/float shaders in your shading trees.

[Anonymous]

Thanks Stephen. Just to be sure, this suggestion below only works for Arnold 5?

'In general, you can either assign a default shader to a custom AOV, or you use the aov write color/float shaders in your shading trees.'

[Stephen.Blair]

You can do that stuff in Arnold 4

Light Path Expressions are Arnold 5 only

[Slava_91]

For working with light group in arnold 4 you need alShaders, only alSurface supports lightgroup in a4, but they are not very practical, so better upgrade to Arnold 5