emitter size / light distribution issue

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wojtek-w
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emitter size / light distribution issue

Post by wojtek-w » Thu Aug 14, 2014 11:24 pm

hi everyone!,
it's been a while since my last visit and i'm glad i'm back.

Here's my try of an evening scene with cold/warm light mix.
Unfortunately i'm not able to set light propely. There's still a lot of noise from the external lights.
The attached image has less than 400 spp but it's not my first attempt (i tried diffrent settings) and even with 1500 spp problem is obvious.
I know that increasing emitter's power helps but i'm affraid not in this case:
Current power of external lights is set to 10,000,000 , efficacy is set to 200, gain (in material settings) is set to 10
inner lights' settings: power 5,000,000; efficacy: 200; gain:3
overall lighting is evening sun (time is set to 19:44)
In render sun layer's gain is lowered to 0,5, internal light layer's gain is 1 and external light layer's gain is 0,1
I don't know if further increase of external light power makes any sense. I belive the size of emitters maybe a problem but i'dont know how to trick / hack this.
Any idea how to improve settings to obtain more or less clear render? I'll appreciate any suggestion.
Attachments
night_140814d.jpg
about 390 spp; still lot of noise from external lights.

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Zom-B
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Re: emitter size / light distribution issue

Post by Zom-B » Thu Aug 14, 2014 11:35 pm

wojtek-w wrote:I believe the size of emitters maybe a problem but i'dont know how to trick / hack this.
Yes, increasing emitter size is a good way to speed up convergence, while keeping polygon count as low as possible!
wojtek-w wrote:Any idea how to improve settings to obtain more or less clear render? I'll appreciate any suggestion.
Yes!
your LightLayer trick is the way to go, and yes, you can push it even further (emitter strength x 10, and LightLayer intensity down to 0.01)!
You can clearly see that your ground light cause still to much noise.

Do you use ArchGlass for your Glass in this scene?

BiDir PT could perform here best because of the small light emitters in the ground...

Also consider to do two renderings with Sky+Sun and another with the mesh lights and then combine both in PS or Gimp.
Having your sun+Sky rendered also helps tweaking the final stufff for the meshlight rendering, with more CPU power on the meshlights!
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wojtek-w
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Re: emitter size / light distribution issue

Post by wojtek-w » Fri Aug 15, 2014 12:55 am

thank You Zom-B for such fast answer!

I have few more question though (for You or anyone who can answer).
1. what is a relation between emitter power and area? If I have first emitter 1m2 and other 0,1 m2 then should i set 10x more power to smaller one? Does it work that way or is it more complex?
2. Is there any limit for emitter power? Can i set 1,000,000,000 or higher?
3. What is the difrerce between emitter's power and emitter's gain?

thank you once again for help

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Zom-B
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Re: emitter size / light distribution issue

Post by Zom-B » Fri Aug 15, 2014 1:27 am

I hate Indigos Light normalization, maybe because I simply don't understand it!
So I never use it :lol:

Yes, for most emittance modes the light output is related to the scale of the mesh...

I use uniform light for 99,9% of my work. Setting the value to 10000000 and if needed I use a small 16x16 colored texture (baked directly in C4D on the fly) and raise the B value for more output if needed.
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galinette
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Re: emitter size / light distribution issue

Post by galinette » Thu Aug 21, 2014 7:37 am

Also, make sure you are using bidir mode.
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