Reason why VRayFastSSS2 is output to VRayLighting element in V-Ray Next

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In V-Ray Next, VRayFastSSS2Mtl is output to VRayLighting element.
Also, the phase function affects the output.

(In V-Ray 3.6, negative values were output to the SSS part.)

Is this a specification change in V-Ray Next?
And for what reason did this change happen?

Simplification of SSS composition?
do not need the following complicated things?
http://www.chaosgroup.com/forums/vbu...746#post560746

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Why hear this? When upgrading from V-Ray 3.6 to Next, it is necessary to change the expression of Beauty composition of the scene containing SSS.

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bump !!!!
Is there a document about this change?

[vlado]

By default VRayFastSSS2 uses a simple approximation to single scattering which is similar to diffuse lighting and is computed in a similar way - which is why it goes into the VRayLighting render element. It generally makes the material appear slightly more realistic. If you set the single scattering to "none", it will go away (see attachments). In previous versions of V-Ray, we attempted to move this contribution to the VRaySSS2 render element and subtract it from the lighting, but it tended to produce negative results sometimes and made more problems than it solved. This is why it was moved back to where it was originally - to the VRayLighting render element. Adding this simple single scattering to the VRayLighting element removes the negative results and makes compositing with the light select elements more predictable.

If you don't need this single scattering approximation, you can set it to "none".

Best regards,
Vlado

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Hello, Mr Vlado

It is necessary to renew the composition formula at the time of using "Simple", but I understood that the specification was changed.

Thank you for the details.

Best wishes,
-------
Yuji Yamauchi
OakCorp Support

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Question. Even if single scattering approximation is "none", it looks like SSS is calculated.
What kind of algorithm does "none" mode sample SSS.

Brute forced multiple scattering?

What is the difference from Raytraced mode.