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Scattering color of standard volume doesn't affect color of light exitting.

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Message 1 of 4
hkmaincontact
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Scattering color of standard volume doesn't affect color of light exitting.

If an object with a standard volume shader scatters a completely red color, why is the light that comes through to the other side still the same color, as when it entered the volume? If white light enters such a volume, and then all the red wavelengths gets scattered, shouldn't that make the light exitting on the other side be tinted to the more bluish/greenish spectrum? Like rayleigh scattering? I would have thought such an effect would just work with Arnold. Am I missing something?

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Message 2 of 4

The scatter color is the color of the light that gets scattered. So it's red that is out scattered, not white-red.



// Stephen Blair
// Arnold Renderer Support
Message 3 of 4

Exactly... Red is the color of the light that gets scattered (In this example).

So white light enters. The red wave lengths of the white light gets scattered. The rest gets through (Or gets absorbed). So that leaves primarily blue/greenish wavelengths getting through. Yet the light getting through has the same color as when it entered, unless I artificially color it with the transparency channel of the volume shader.

It feels like the shader is not very physically based, but just scatters a color. Not the light itself.

Right?

Message 4 of 4

I noticed the same thing 🤔

Technically the more a light ray travels in a volume that scatters a certain color wavelength, the more the surviving not scattered light that we can see from the light source will be tinted of the opposite color. That's why the sun appears yellow at  midday and more and more red the lower it gets, all the blue wavelength (and green too at sunset) has been "stolen" from it by the sky. 

@Stephen.Blair Have you ever seen a Sunset Egg? That shows exactly what the OP was talking about. 

SunsetEgg.jpg

I suspect it is not possible to create a mini "Rayleigh sunset effect/ sunset egg" in Arnold.. at least not straight out of the box. Would be cool though, and more physically correct.

Or maybe there is a trick to get something similar

If not it would be neat to add it to a later version maybe 😄!

 

 

 

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