How to use AO with aiStandardSurface shader?

[litote]

Is there a way to incorporate ambient occlusion shading with an aiStandardSurface shader to render it within Maya? I know you can output a separate AO pass for compositing in other apps, but how do you use it withing Arnold to add shadow detail on top of an aiStandardSurface shader? Can you input an AO map or combine it with the aiAmbientOcclusion shader in some way to render within Maya?

[lee_griggs]

You could use a Mix shader. I am curious as to why you are doing this?

[litote]

@Lee Griggs Not sure myself. I suppose the point of AO layers is to give options in compositing to further define geometry with the shading, so probably you would not normally try to mix it in Maya, but render an AO pass as an optional compositing layer? I notice some texturing apps like Megascans have an AO map, so presumably that is what it is for, or for resource-cheap lighting in a game engine?

[litote]

I tried using an aiMixShader but this blends them, making them faded. I think using an aiMultiply node is the way. Am I missing something?

[lee_griggs]

Yes probably for game engines. I wouldn't touch it myself.

[lee_griggs]

If it works then go for it. Can you share images of what you are doing?

[litote]

@Lee Griggs

This is the node network I used for Arnold 5. The AO map is added to the aiImage node linked to the aiColorCorrect node, which I use to lighten the shadows to suit, using the Gamma parameter. The beauty/diffuse map is in the second aiImage shader also linked to the aiMultiply node -- this composites the AO map together. The third aiImage node has the normal map which connects through the aiNormalMap node:

[nalbright6DJJ7]

Ambient Occlusion should only modify the results of indirect light.  As such I plug my AO maps into the aiStandardShader.Advanced.indirectDiffuse and indirectSpecular. 

If you're mixing AO with your albedo, you're suggesting that even when a light ray is directly hitting your pixel, the light is somehow not influencing it, which is wrong.

[biboxih944]

Step 1: Create a new scene and populate it with objects  3 more pictures. Go to File and click on New Scene.

Step 2: Create a new render layer. and 2 more pictures. Great 

Step 3: Create an occlusion pass. 2 more pictures.

Step 4: Render, Adapt, Render, Adapt, Render. 6 more pictures.