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ambient occlusion
show user profile  zeefusion
After viewing some examples there seems to be variations in the intensity of the resulting AO. Some I have found are a dark grey and others are very white such as these:

Is there a correct intensity? Does a lighter AO give better/worse results.


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8/8/2012 12:54:37 PM (last edit: 8/8/2012 12:54:37 PM)
show user profile  Westcoast13
I'd prefer it to look like the lighter one. I only like my AO to be in the corners etc. With the darker one you would have to lighten your image a lot and you'd lose a lot of the AO pass then.

All IMO, other views more than welcome though!

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read 2732 times
8/8/2012 12:56:50 PM (last edit: 8/8/2012 12:56:50 PM)
show user profile  Dave
Well it's just light/shadow. There would be no standard way of doing things as it will vary for each scene. When we bake the AO into the diffuse we usually do it on a multiply[blending mode] layer, so white = nothing. If you rendered your AO with such a large degree of shadow falloff, then the whole scene will darken as a result.

It's worth noting that your top picture there might not be a grey-AO, but rather an AO much like the one underneath, and just applied to a grey material. Since you don't see the white, (shadow is the only important thing), you can literally have any colour mixed with an AO.

It looks to me like we're actually looking at two very similar AO passes in your examples. The only difference is that one has been applied to a standard grey material, while the other is a raw render.

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8/8/2012 1:05:29 PM (last edit: 8/8/2012 1:05:29 PM)
show user profile  zeefusion
Makes sense, thanks for the help guys. I always try and get a more white result but I was curious :)
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8/8/2012 1:10:25 PM (last edit: 8/8/2012 1:10:25 PM)
show user profile  STRAT
aye. AO is quite a subjective pass. it's your choice. there is no right or wrong. there is no this or that way. each method is the same as the next. just depends on how you want your final image to look.

they can both give equal results. what's important is how you layer and blend in photoshop or post. this is what best controls AO density and feel.

the second image is more akin to a conventional AO pass, due to it's contrasts. layering would be easier and more effective in this one.

a lot of peeps say you shouldnt use it anyway. Well, as mentioned, it's subjective. Personally, i always use a touch of it. but very very subtly and locally. it can make the image. conversely, it can ruin your image.
Nubes over use it and it make's their imagery smudgy and dirty and fake.


read 2716 times
8/8/2012 1:12:47 PM (last edit: 8/8/2012 1:13:26 PM)
show user profile  zeefusion
I have to admit I don't always use it as from what I understand, most up to date rendering solutions have fixed the AO issue and there is little need for it. It is more of an after thing to increase the look of your image. But as you rightly put it, it can also ruin renders as well.
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8/8/2012 1:19:42 PM (last edit: 8/8/2012 1:19:42 PM)
show user profile  BishBashRoss
Aye, agree with Strat. The second one is better as you are at less risk of getting banding as it doesn't need a levels/curve correction to get the pure white areas. Also like Dave says the first one doesn't look like just AO.

read 2707 times
8/8/2012 1:21:37 PM (last edit: 8/8/2012 1:22:18 PM)
show user profile  zeefusion
Here is a different darker example. I think this is the result from one of the scripts that create an AO pass.

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8/8/2012 1:27:17 PM (last edit: 8/8/2012 1:27:17 PM)
show user profile  STRAT
thats a very spread or diffuse AO. something more to show as a proof render rather than a useful AO pass for post work

also, on what you mentioned, there is or was no broken issues to be fixed. ao has always been. it's just GI render engines and peeps's use of them are becoming better than before. less use of AO is needed generally.


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8/8/2012 1:29:11 PM (last edit: 8/8/2012 1:30:25 PM)
show user profile  Chris123643
yeah the second image looks alot like the ones I do... although Ii don't always bother, it does improve the image most of the time but when it comes to having to edit the original image, it seems a bit too much work to have to re-render the AO pass...

I've noticed the Ambient Occulsion option under the vray:GI settings. Anyone ever use that?

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8/8/2012 1:51:49 PM (last edit: 8/8/2012 1:51:49 PM)
show user profile  ScotlandDave
What you should have with any AO solution ( it`s in AR for C4D can`t remember for MR or VRay ) is the ability to change ray length or radius or similar value, and what that does is control how tight or how wide the AO calculation is - ie a really sharp AO just for tightening up corners etc or a more blanketed effect that covers a larger surface area of the scene and looks more like GI..

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read 2682 times
8/8/2012 1:57:45 PM (last edit: 8/8/2012 1:57:45 PM)
show user profile  STRAT
chris - yup, i subtly use that in almost every render


read 2677 times
8/8/2012 2:13:00 PM (last edit: 8/8/2012 2:13:00 PM)
show user profile  zeefusion
The global AO setting in V-Ray from what I understand is to boost the GI solution. So if you used LC for both primary and secondary the results would be crap but it would render at a good speed. To boost the results you can turn on the AO setting.

So in theory if you used IR + LC or BF + LC you wouldn't necessarily need the global AO setting as the GI solutions are good enough but would render slower compared to the above.

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8/8/2012 2:16:28 PM (last edit: 8/8/2012 2:16:28 PM)
show user profile  STRAT
zee - not per se. no. you can use LC+LC to render perfectly, provided you used the correct settings. no need for AO.

AO only enhances whatever's there.

If you use IR + LC or BF + LC as you say, you wouldn't necessarily need AO at all, but if your samples and settings and understanding how to correctly use those solutions isn't good enough then yes, AO helps.
Using IR + LC or BF + LC wont automatically give you a good gi solution, meaning AO is sometimes required


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8/8/2012 2:22:46 PM (last edit: 8/8/2012 2:24:10 PM)
show user profile  zeefusion
true, it does depend on your settings and of course what you are rendering. I guess it is down to the user and how they want to go about getting a decent render in little time.
read 2656 times
8/8/2012 2:48:40 PM (last edit: 8/8/2012 2:48:40 PM)
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