need help with colored emission

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need help with colored emission

Postby miohn » Sun Mar 30, 2014 10:45 pm

miohn Sun Mar 30, 2014 10:45 pm
Hi,

sorry if this has been already covered, but cannot find it.

If I make a material with texture emission and put a rgb spectrum in
the first slot, I get a colored light.
But its extremly noisy, even if I raise tzhe sampling rate to 2000 or more.

Is there a better way to make a red lightning material?

thanks
Mike
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Re: need help with colored emission

Postby bepeg4d » Mon Mar 31, 2014 6:25 am

bepeg4d Mon Mar 31, 2014 6:25 am
please, could you share some images?
take in mind that the complexity of the emitter geometry it's important in terms of speed and noise.
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Re: need help with colored emission

Postby miohn » Mon Mar 31, 2014 9:28 am

miohn Mon Mar 31, 2014 9:28 am
Hi beppe,

this means, that the geometry needs to be higher polycount
to get less noise?

screen_redlights.jpg
screen_redlights.jpg (32.32 KiB) Viewed 2972 times


I think, I have the RGBSpectrum in the wrong slot maybe?
How should this setup correctly?

regards
Mike
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Re: need help with colored emission

Postby bepeg4d » Mon Mar 31, 2014 10:10 pm

bepeg4d Mon Mar 31, 2014 10:10 pm
hi,
the cyan pixels are overexposed, if you decrease the power a lot, the noise should go away.
the problem is that the first slot has a double function, texture slot for coloring the light, but also efficency that is related to the scale of the emitter. by default, the efficency is set to 0.025 for a standard artificial emitter, so if you use an rgb you should lower the value in SLV mode to something near 0.025.
if you use a texture, lower the power ;)
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Re: need help with colored emission

Postby miohn » Tue Apr 01, 2014 12:12 am

miohn Tue Apr 01, 2014 12:12 am
Hi beppe,

thanks! And yes you're right!
Decreasing the power to about 0.5 or 0.05 ... kills all noise.

But I get too less lighting and no blooming effect.
I need a much more powerfull light.
So only way is to combine it with an extra area light
which is set unvisible to camera?

regards
Mike
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Re: need help with colored emission

Postby atome451 » Tue Apr 01, 2014 8:25 am

atome451 Tue Apr 01, 2014 8:25 am
You should keep de power of the emiter to a higher value but use a more darker red, as suggested by bepeg4d.
If you use a texture, change the power of the ImageTexture, not the power of the emiter.
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Re: need help with colored emission

Postby miohn » Tue Apr 01, 2014 9:01 am

miohn Tue Apr 01, 2014 9:01 am
ahh o.k. now I got it!

thanks very much!
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Re: need help with colored emission

Postby roeland » Tue Apr 01, 2014 8:49 pm

roeland Tue Apr 01, 2014 8:49 pm
What you are seeing here are artefacts of how Octane converts the RGB colours to a spectrum and back. The color coming back for the light source is not exactly red, but it will be slightly more magenta or yellow. And since the light source is much brighter than the maximum brightness displayed in the tone mapped image, it will get clipped to magenta or yellow instead of red. You can try a few things to improve the appearance:

You can set the color to not exactly red, but add a small amount of green or blue. This will make the color rendered for the light source clip consistently to yellow, magenta or white, depending on which colour you add.

You can also use a Gaussian colour instead. A wavelength setting of 0.850 and a width of 0.045 give a very saturated red, which will always clip to red if it is too bright.

Alternatively you can tweak the "saturate to white" input in the camera tone mapping settings. If you set it slightly above zero, very bright objects will tend to be displayed as white, so you also don't see the noise anymore.

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Re: need help with colored emission

Postby miohn » Tue Apr 01, 2014 10:07 pm

miohn Tue Apr 01, 2014 10:07 pm
Hi Roeland,

thanks for your detailed explanations!
Will try them all.
But in the end, there is still PSD available for
final adjustments.

thanks
Mike
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Re: need help with colored emission

Postby nfms » Tue May 12, 2015 11:28 am

nfms Tue May 12, 2015 11:28 am
roeland wrote:What you are seeing here are artefacts of how Octane converts the RGB colours to a spectrum and back. The color coming back for the light source is not exactly red, but it will be slightly more magenta or yellow. And since the light source is much brighter than the maximum brightness displayed in the tone mapped image, it will get clipped to magenta or yellow instead of red. You can try a few things to improve the appearance:

You can set the color to not exactly red, but add a small amount of green or blue. This will make the color rendered for the light source clip consistently to yellow, magenta or white, depending on which colour you add.

You can also use a Gaussian colour instead. A wavelength setting of 0.850 and a width of 0.045 give a very saturated red, which will always clip to red if it is too bright.

Alternatively you can tweak the "saturate to white" input in the camera tone mapping settings. If you set it slightly above zero, very bright objects will tend to be displayed as white, so you also don't see the noise anymore.

--
Roeland


Thanks for this golden advice, the gaussian colour does the trick perfectly.
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