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Ambient Occlusion required?
show user profile  zeefusion
I have just been thinking about Ambient Occlusion. There is a lot of talk about it a few years a go about it being necessary to add realism to an image. How ever these days it seems to be used as an artistic tool.

Am I right in saying modern rendering technology now includes calculating Ambient Occlusion effects anyway through GI without having to then do it manually? Or is it still needed?
read 3995 times
12/13/2011 4:44:36 PM (last edit: 12/13/2011 4:47:04 PM)
show user profile  Coxy
I still use it, mainly because some times I like to save as much time with MR as possible and also because it is so quick for a little added detail. I think it is a situational thing.

i.e There are not always times when you can stick 4-7 bounces on an image with no filtering and very high rendering settings and sit there for 8 hours per frame waiting for it. Sometimes you might need to stick with GI, a skylight and some shittier FG settings and use the AO pass to fill in some of the details missed.

Also it works as a really nice mask for materials, dirtying up the corners of brickwork etc.

I think there is always value in having things that you have lots of control over personally. I don't think you can uniformly say it is or isn't required, just depends on the problem.
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12/13/2011 7:49:21 PM (last edit: 12/13/2011 7:52:26 PM)
show user profile  Mr_Stabby
AO, GI and FG essentially all do the same thing, they just all have a different approach to it. GI traces light from light source to surface, AO traces light from surface to light source (or ambience in most applications).

Imagine a curve of exponential growth, in case of GI you have simple geometry (like surfaces that face the light directly) on the high end of the curve and difficult geometry (like crumpled paper) on the low end. The curve represents how much "attention" they are getting in relation to how much they need. While in theory if you shoot enough photons you will eventually get all the details covered but as you can imagine this is very inefficient.

To the rescue comes AO, essentially its trying to treat every triangle equally by starting with the surface. This communist concept while noble also has an inherit fault - light doesn't travel backwards. Because of this it has no idea which way to shoot its rays or photons or whatever its currently called. Theoretically it could just shoot them in every direction until it reaches the light itself and deduct the correct pattern from there but this is even more inefficient then trying to capture every detail with GI. So what can it do? Well there is a type of light that travels in every direction at the same time while occupying every point in space - diffuse. By exploiting that approximation it can get quite accurate and speedy results in the small scale while being notoriously inefficient in the large scale.

As it stands today FG, AO and GI are still separate entities but in advanced rendering engines like MR can be combined to get good results all around. So ya you still have to turn it on, specify its scope and impact manually. They could be combined into a single global lighting system but that way they would just lose flexibility for no real benefit over the current modular implementation.

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12/13/2011 8:10:27 PM (last edit: 12/13/2011 8:10:27 PM)
show user profile  zeefusion
Thanks both. That was very helpful.
read 3950 times
12/13/2011 10:34:35 PM (last edit: 12/13/2011 10:34:35 PM)
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