Need help with Ambient Occlusion pass

[Barkwally]

Well as far as I know, the beauty pass, is everything.
Except the occlusion.
So you have reflection, transparency, shadows, everything.
And then you add the occlusion to get some extra candy. :D
I always render the occlusion as a separate pass, so that I got more control in the comp afterwards.

[spiralof5]

Thank you, I've read that but there is something I'm still not grasping.

yeah I guess I understand............but it still doesn't make a lot of sense. Think of it this way.

Occlusion is to help do away with direct lighting as is Final Gathering. Final gathering does a heck of a lot more than just darken corners in a lit room. Why would I want the look of a direct lighting when what I'm trying to achieve is the exact opposite?

I don't see how throwing ambient occlusion on top of direct lighting helps my situation?

[Barkwally]

Well occlusion is only there to help you get more detail out of your scene.
To get the feeling of depth.
Its not for lighting.
You have to try it to see the difference.
And the thing with doing it as a separate pass is that you can tone it down if you want afterwards in comp.

[yenvalmar]

and also render blazing fast... you should simply bake your final gather occlusion beauty etc into texture maps. look up texture baking theres a ton of threads about it.

as to the definition of a beauty pass, you are very confused. if that uses direct or indirect lighting is a matter of how you set your render globals. configuring a separate beauty pass and occlusion pass will INCREASE render times. unless you also change the settings of the beauty pass to be faster than they were before. you can allow for lower settings on the FG to save render time, if you know you are going to use an occlusion pass also to add the fine details, and in fact this is one of the reasons its commonly used at all, aside from that it also will further enhance even a really nice beauty pass because the AO shader just.. makes it look better when you put it on in post as another pass :)


you will need to use many lights for faking effects of indirect illumination, if you want the indirect look without ever using true indirect lighting, either computed at render time, or baked into texture maps, on your beauty pass. it takes a lot of manually creating and tweaking normal lights to acheive a good render, thats why we rarely saw it before GI IBL occlusion etc became common.

it requires an artistic eye and a knowledeg of real life lighting, to know everything that it SHOULD look like, to fake it all with a million spot lights. but it can be done.

[spiralof5]

yeah I hear ya.

I read something that better explained what I meant I guess. Since ambient occlusion in all purposes is really the occluding of ambient (light), than it really should be used with an ambient only pass, a direct lighting pass with no shadows, and a shadow pass and an ambient occlusion pass (I think that's what it said.)

For purposes that I am using now though, can just do with an ambient occlusion pass. Lots of people are using the mib_fg_occlusion but for now its just not working. I have an enclosed structure, and I feel like the mib_fg_occlusion is only taking it's sample points from my environment (i'd have to test this)

The only reason why I say so is that my scene is very dark, almost to the point that too much is being occluded (just black). Since mib_fg_occlusion doesn't have any parameters, I can only assume I did it right.

[spiralof5]

also, what am I supposed to do for reflections? How do I get the occlusion to happen for that?

thanks,

Scott

[tedious]

also, what am I supposed to do for reflections? How do I get the occlusion to happen for that?

If you want to see reflections of the occlusion, then when you create the layer that'll be your ambient occlusion pass, don't use the preset, don't assign ambient occlusion as the shader for the whole layer. Instead, go into that layer, pick the regular models, and assign the amb occ shader to the non-reflective models, then assign a purely reflective shader to the reflective models. That way you'll get an ambient occlusion pass that includes reflections of occlusion where you want it.

You don't really want the ambient occlusion to be darkening anything but the ambient/diffuse shading in your scene anyway, if it darkened transparent, refractive, reflective, or incandescent surfaces it could just look weird.

-tedious

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