Is there a way to make the AO pass "alpha\refractive" sensitive ?

[geoundici]

Hi everyone,

I'm sorry if there's already something about this and I haven't found, but I have this question:

since I'm working with files and objects from different modellers in this architect studio, I find myself with a lot of objects that have a glass material in them ( tables, furnitures etc), but I can't assign them the same "new" material, they have differences and details that I cannot substitute with my own materials (multi sub material). So when I make an override AO passage, I can't turn off with a click all these glass materials, as they have different materials applied, or are supernested\grouped objects. It's a mess, I know, but that's my situation, so: is there a way so I can do just ONE AO override material passage, with the AO "sensitive " to the "refraction\alpha" characteristic of all the materials? So with all the materials already setup by others, and I have dozen..., I could just make this override without turn off all the glass objects in my scene. I'm in a hurry and I can't clean up all the scenes they are giving to me, wiìhich could be the best scenario, of course.

thanks for any help.

[maru]

As far as I understood your problem is that you cannot render AO pass of objects that are transparent (e. g. glass), even when using CTexmap render element. Unfortunately I don't think there is currently any easy fix for this.

My idea would be to put mtl override on the whole scene with some random grat material, and then render the CTexmap element with AO assigned.

You can then use "render only elements" option to render the AO pass only, it should render much faster than the beauty. 

[Jpjapers]

would it be possible to use a slot similar to the the material override slot that would stop a certain material from being overridden i.e. the glass material? That way it with a CTexmap of AO the glass would still render as glass/completely transparent?

[Frood]

As far as I understood your problem is that you cannot render AO pass of objects that are transparent (e. g. glass), [...]

I think the opposite is his problem: He wants no AO of/on objects with highly transparent materials which is reasonable (if refraction + glossiness are both high). So his idea is to link AO exclusion/effect to transparency - would be perfect in this situation. This problem is as old as AO shaders are. Vray has a "work with transparency" checkbox, MR has at least object ID exclusion (self and others).

A nice feature request could be to add at least material ID and/or object ID excludes to the (corona) AO shader but it would not help here since at least all transparent materials have to get some ID assigned. But if the AO shader could respect transparency/translucency besides opacity it would help in those situations generally.

Geoundici, maybe the different "glass"-materials have something in common so that another pass could be used to mask your AO pass out? This way at least occlusion _on_ those materials (but not from) could be eliminated. Depending on your scene and materials a (clamped/leveled) refraction pass or even albedo will do it.

Good Luck!

[Jpjapers]

Is the problem that the stuff behind the glass doesnt get any ao because realistically in the ao pass the glass is solid white and therefore no ao is visible through it?