Ambient Occlusion behind Glas

[Schmidhuber]

Hello everyone,

to get AO behind glass I have done 2 renderings so far. One rendering with glass, one without glass. I then used the 2 renderings in Photoshop.

Is it possible to render AO behind glass in one rendering process or is there another possibility?
Thanks for your input

[skientia]

It seems that there was an omission of what is presumably an AOV compositing setup.
If so, what are the intentions and what does the setup consist of?

Any particular reason(s) for using AO?
It's an obsolete rendering method, present for some edge cases.

[frankmci]

Internally, Octane considers AO and Refractive Rays as different categories of illumination. Octane Glass/Specular Materials by default allow Refractive Rays to pass, but not Ambient. I suggest you use the Ray Switch node in the Opacity channel of your glass material to make it at least partially transparent to AO rays. Depending on the color/thickness of your glass, you may need to experiment with what value between 0-1 looks correct to your eye.

[Schmidhuber]

Ambient Occlusion should be multiplied in Photoshop as an extra layer.
I hope the pictures make it more understandable - it's about AO behind the glass - not in the glass.

[skientia]

Under the assumption that AO AOV is used as the "shadow-booster technique", and given the lack of single-checkbox option for this scenario, compositing is seemingly the most straight forward approach to have such control in post with necessary AOVs and masks.

[frankmci]

Ah, I thought you were trying to avoid compositing all together and wanted control of the AO through the glass surface.