GI vs AO vs GI+AO Vegetation Comparisons

Started by WAS, September 05, 2018, 07:28:37 PM

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WAS

Sorta just an test looking on what the effects of GI and AO are on scenes without much global representation.

It almost feels like GI + AO is what you'd see to the naked eye with strong summer sun on a patch of vegetation like that, but may be just my preference. Interested in your interpretations.

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GI + AO at 1
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GI + AO at 0.5
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GI + Contrast & Atmosphere Adjustments
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Oshyan

GI + AO looks to me like an HDR-processed image. The shadows seem too light to me, although it's hard to be sure what the sun angle is and thus what the environment contribution should be. That being said, it's also odd that the GI+AI is overall brighter than either one. I guess you are doing this with two Enviro Lights? In that case I guess putting them both at 0.5 strength might make for the more "correct"/matching exposure? I'm not sure.

In any case the current GI approach is cache-based and not great at fine details. A pathtraced version of this image ought to look better/more realistic. I'm curious if you would find that to be the case though. Can you share the scene and objects?

- Oshyan

WAS

#2
Quote from: Oshyan on September 05, 2018, 07:38:11 PM
GI + AO looks to me like an HDR-processed image. The shadows seem too light to me, although it's hard to be sure what the sun angle is and thus what the environment contribution should be. That being said, it's also odd that the GI+AI is overall brighter than either one. I guess you are doing this with two Enviro Lights? In that case I guess putting them both at 0.5 strength might make for the more "correct"/matching exposure? I'm not sure.

In any case the current GI approach is cache-based and not great at fine details. A pathtraced version of this image ought to look better/more realistic. I'm curious if you would find that to be the case though. Can you share the scene and objects?

- Oshyan

Yeah it is sorta like an HDR image. Sun is at default position; 300 by 25, with default camera direction, just looking down into the vegetation. I'm rendering a version with half intensity on both enviro lights to see if that's a better balance than doubling up. So far it seems shadows are crisper.

Though to that effect, to the naked eye outside looking at the vegetation in the sun right now, there is a LOT of ambient glow from translucency and the shadows don't look that dark. I'd imagine a camera looking at it would create those dark shadows through contrast focusing. Shadows in the bushes are pretty much interior lighting intensity levels.

Matt

#3
I do prefer the versions with the additional AO light. But I think this is only because the original scene is a little underexposed for the shadows. I think that if you simply increase exposure and/or make the atmosphere more hazy you would get a more realistic result. The AO light doesn't account for bounced light within the vegetation, whereas the GI light does. You can also push the GI light above 1, but that isn't quite realistic either.
Just because milk is white doesn't mean that clouds are made of milk.

WAS

#4
You're right. I added some comparisons with higher haze settings and tad more contrast. Much more natural, while obtaining a "ambient occlusion" look.

Dune

I think I agree with Matt in that the additional AO gives it just a bit more reality, but it also depends on the species of plants how dark shadows should be. Some leaves let more light through than others, more reflective leaves will have more reflected light in the shadows as well.
I tend to up GI to get lighter shadows on the whole, and also decrease opacity of the leaves to get less dark shadows. Adding more haze or more cirrus also helps in getting a tad more light in shadows, so I use that as well.

WAS

Quote from: Dune on September 06, 2018, 02:12:40 AM
I think I agree with Matt in that the additional AO gives it just a bit more reality, but it also depends on the species of plants how dark shadows should be. Some leaves let more light through than others, more reflective leaves will have more reflected light in the shadows as well.
I tend to up GI to get lighter shadows on the whole, and also decrease opacity of the leaves to get less dark shadows. Adding more haze or more cirrus also helps in getting a tad more light in shadows, so I use that as well.

I tried some opacity and got a few holes at a reasonable setting so just left it alone from there. The last tests with some thicker haze, tad more glow on haze and balancing the lightness it creates with contrast bumped 10% looks pretty snazzy, simulates that whole AO look. These veggies are pretty translucent in direct sun being nrwgrowth ground cover. Could go further with the haze or like you said a localized Cirrus or something if you have some distance to see. Over was a fun little test though

Dune

If you lower opacity with a pf input holes are likely, as some areas will drop below 0.5000001. I just lower it without any input (unless I need the holes).

ajcgi

It's a lovely test scene either way. Excellent attention to details as always. ;)
I think they all have their merits depending on the shot you're working on.
Personally I'd go for the more contrasty top GI only one, but that's possibly my photographic preference.

WAS

#9
Quote from: ajcgi on September 07, 2018, 06:04:56 AM
It's a lovely test scene either way. Excellent attention to details as always. ;)
I think they all have their merits depending on the shot you're working on.
Personally I'd go for the more contrasty top GI only one, but that's possibly my photographic preference.

Thanks, yeah I try to avoid photographic effects like contrast and darkening over the naked eyes more middle ground. This I was basing testing off lighting in grass here. In the sun there were just no strong shadows ass the vegetation was just too translucent for the strong sun, and the model literally contains the same exact species including a random skunk cabbage coming up. To the naked eye it actually looks a lot like the AO only. Summer light casting see yellows, and dark shadows only really occuring deep within the grass and leaves.