I cannot figure out how to simply output a particular material to its own AOV. I read the documentation, but it's all about how to replace one thing with another thing. I.e. how to create an AOV for object IDs, overriding the object material with a Utility shader. Well that is fine, but it does not help me understand how AOV Write nodes work in general. So I can't apply those general principles to my specific situation. The documentation just leads me down the garden path to a place I don't want to be.
What I need is to simply render out a particular material to its own AOV. I need to do this with emissive materials because they are not showing up in my light group AOVs.
The thing is, I thought I could just create an AOV Write RGBA and connect the output of an Arnold Standard Surface to both the passthrough and the AOV_input of the AOV Write RGBA. So the material will show up in the beauty pass as well as the AOV. But I cannot connect the output of Arnold Standard Surface to the AOV_Input slot. It accepts a map, but not a material? This is very strange.
Please tell me how I can output a particular material to its own AOV.