Hiding an opacity mapped plane from an AO pass

[SonyBoy]

This is another thing in Vray like the "Affect Channels" shader rollout that seems to confuse everyone and I wonder if there couldn't be a better more intuitive implementation of it.

I have some simple logo glyphs driven by a texture that are opacity mapped to a plane, with alpha driven by the texture's luminance. In the beauty pass this works great, however I'm unable to figure out how to prevent the plane from contributing to the AO pass in the same render. I simply want this plane to be ignored completely.

What is the correct setup for this? Neither creating inclusive or exclusive sets for the pass, either on the dirtmap OR on the render element has the desired effect, with just about every possible outcome apparently an option except the one I want -- simply to make the plane invisible to the AO calculations. Reading the docs for this stuff always makes my head spin and totally lacks visual examples to help understand the dizzying array of inclusive/exclusive options. And I totally fail to understand how the "Affected By" and "Exclude" sets work together (at least as far as I decipher from the opaque docs, there is some relationship between these two sets).

Can I completely ignore the exlcusive set on the render element, and only use the sets on the dirtmap? Can I use either? Do I have to set BOTH up, or do they cancel each other out? Is there any difference between creating an inclusive or exclusive set (except for the obvious?).

Why is this so difficult, and why isn't it possible to simply exclude objects completely from the universally used AO pass -- EASILY?

[hermit.crab]

VRayExtraTex works by applying a single texture to the whole scene. Objects within the VRayExtraTex's exclude list will not be assigned the selected texture.
VRayDirt's Exclude list disables calculations for specific objects by not shading them, while Affected By considers excluded objects as invisible (calculation-wise).
If you want an object entirely removed you should render the AO separately with the objects hidden.

Hard to say what is the correct setup without an understanding of what you're trying to achieve. The question is what do you mean by invisible?

[SonyBoy]

Thanks Aleksandar, however I'm afraid I find your explanation just as confusing as the documentation. You say "Affected By considers excluded objects as invisible (calculation-wise)". This suggests that these objects would therefore not be included in ANY calculations, and would not contribute to AO shading with the dirt map. But this is not what I am seeing. See the attached set of images to explain my specific problem. I want the plane to have zero contribution to the AO pass. No combination of exclude lists and/or using the "Affected By" list seems capable of producing this result.

Are you saying this isn't possible and I have to remove the mapped plane from the pass entirely? This obviously necessitates a completely separate render, which can be highly expensive. This begs the question then what on earth are the exclusion lists for. This is pretty common scenario and one where I'd expect some sort of ability to flag the plane to be completely ignored during the AO pass calculations so that it is effectively invisible to the renderer.

[vlado]

The VRayDirt texture has an option “Ignore invisible objects” which should help opacity-mapped objects.

Best regards,
Vlado

[SonyBoy]

THANK YOU Vlado. Turns out toggling that option on gives me precisely the result I wanted. No messing about with exclusion sets etc. Easy when you know how