Author Topic: GI+AO=Realism  (Read 5902 times)

Offline Mohawk20

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GI+AO=Realism
« on: April 18, 2009, 09:36:56 PM »
I was just converting some XFrog bushes to tgo, and rendering preview images (so I can easily pick which I need later on), when I decided to try something I read about a while ago.

Someone achieved realistic lighting by adding a second envirolight and setting it to Ambient Occlusion, while the first envirolight was still in Global Illumination.
I tried and below is my result.
Just a simple, basic scene. Only extra nodes to default is 3 XFrog buxus objects and an extra envirolight (with default settings of 1 for all sliders).
The first is only GI, the second is GI+AO, the last one is only AO. GI+AO gives the best result as it's a bit lighter and thus has a bit more detail.
« Last Edit: April 18, 2009, 09:52:16 PM by Mohawk20 »
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Offline Oshyan

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Re: GI+AO=Realism
« Reply #1 on: April 18, 2009, 10:29:33 PM »
I wonder if a similar effect could not be achieved simply by increasing Strength on Surfaces for the Enviro Light. Also did you record render times for these different scenes?

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Offline Mohawk20

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Re: GI+AO=Realism
« Reply #2 on: April 18, 2009, 11:01:41 PM »
Did you record render times for these different scenes?

No, but I believe it was between 8:50 minutes and 9:30 minutes. I can render them again to check...

If I increase the strength, should a setting of 2 for all options be enough, as it now is 1 for all options, only twice? It would seem logical...

Tomorrow I'll render comparisons with GI at 2 and AO at 2, and post them together with a render of both at 1 as above.
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Offline Oshyan

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Re: GI+AO=Realism
« Reply #3 on: April 18, 2009, 11:11:28 PM »
Sounds good. Be sure to record render times too!

- Oshyan

Offline cyphyr

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Re: GI+AO=Realism
« Reply #4 on: April 18, 2009, 11:48:30 PM »
tried this in my latest Ground cover mash up, works great, though the render times are up :)
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Offline JimB

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Re: GI+AO=Realism
« Reply #5 on: April 19, 2009, 12:39:22 AM »
A technique I tried with really nice results (not with Terragen, but XSI and Mental Ray) was to mix AO and GI based on direct sunlight negating the AO where it hits a surface. Gives a really good result, as AO can sometimes be too much, but when only visible in what are logically the shadow areas can give a nicer "feel" to the image.
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Offline Seth

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Re: GI+AO=Realism
« Reply #6 on: April 19, 2009, 02:35:05 AM »
I used this lighting technique several times with success... i just suggest to lower the Ambiant occlusion...

Offline Mohawk20

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Re: GI+AO=Realism
« Reply #7 on: April 19, 2009, 07:19:27 AM »
I just suggest to lower the Ambiant occlusion...

I thought about that as well, and will do that in a next scene, but later today I'll just do the quality comparisons.
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Offline cyphyr

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Re: GI+AO=Realism
« Reply #8 on: April 19, 2009, 11:06:37 AM »
The Ground Cover Mashup had AO at 0.7 and GI at 1.3 on surfaces and 1, 1 on atmosphere. Actually I'm not too sure what the atmosphere settings do for closup up work, I suspect they only effect cloud layers and such.
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Offline Tangled-Universe

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Re: GI+AO=Realism
« Reply #9 on: April 19, 2009, 02:59:51 PM »
I use this technique quite much. Usually I keep the GI as is, but when I increase it, it is never above 1.5, usually around 1.25.
Like Franck (Seth) said I also lower the AO. Often the AO is set at 0.25 - 0.5.
There's an increase in rendertime, but not extreme.

Offline Mohawk20

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Re: GI+AO=Realism
« Reply #10 on: April 19, 2009, 07:29:20 PM »
Well, I did some rendering and here are the results.
I rendered at 0.75 detail with 1,1 GI in the render settings, on only one core, as I was rendering another project on the other core.

     GI @ 1 strength= 0:08:37s
     GI @ 2 strength= 0:08:42s
    AO @ 1 strength= 0:08:25s
    AO @ 2 strength= 0:08:27s
GI+AO @ 1 strength= 0:10:54s

And below the renders in the same order.
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Offline Seth

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Re: GI+AO=Realism
« Reply #11 on: April 20, 2009, 02:48:27 AM »

Like Franck (Seth) said I also lower the AO. Often the AO is set at 0.25 - 0.5.


same here ^^
oh and you may want to apply the AO only to the surfaces and not to the atmo... sometimes you can have good result too ;)

Offline moodflow

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Re: GI+AO=Realism
« Reply #12 on: April 20, 2009, 07:35:01 PM »
Yes, you just have to play around with the GI settings until the scene "pops"!   8)
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