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How to use AO with aiStandardSurface shader?

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Message 1 of 9
litote
32682 Views, 8 Replies

How to use AO with aiStandardSurface shader?

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?

8 REPLIES 8
Message 2 of 9
lee_griggs
in reply to: litote

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

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 3 of 9
litote
in reply to: 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?

Message 4 of 9
litote
in reply to: 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?

Message 5 of 9
lee_griggs
in reply to: litote

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

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 6 of 9
lee_griggs
in reply to: litote

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

Lee Griggs
Arnold rendering specialist
AUTODESK
Message 7 of 9
litote
in reply to: 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:

1113-ao.png

Message 8 of 9
nalbright6DJJ7
in reply to: litote

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

 

AO.PNG

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.

Message 9 of 9
biboxih944
in reply to: litote

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.

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