[Bf-cycles] "Is SSS ray" output and ray visibility

Matthew Heimlich matt.heimlich at gmail.com
Sat Jan 17 15:42:39 CET 2015

I think what Greg is going for is a lamp that would only affect glossy
materials, for artistic highlights on eyes and such. Currently this is
impossible because there's no way to turn off the influence of a lamp on a
material with SSS. So it's not so much a request for turning off the SSS of
the material, but rather the influence of the individual lamp.

On Sat, Jan 17, 2015 at 9:33 AM, Sergey Sharybin <sergey.vfx at gmail.com>

> That's probably possible, but sounds a bit malformed. Internally SSS ray
> only exists in medium with SSS shader and used for light attenuation in the
> medium. From this point of view SSS ray visibility makes no sense sine
> disabling it would basically mean removing SSS closure from the object.
> That's not what you want i bet.
> So main question is what you consider SSS ray.
> Is it any ray after subsurface transmission as SSS ray? This is somewhat
> weird for scenes when having multiple SSS objects, especially when having
> smoke.
> Or is it first bounce after SSS transmission as a SSS ray? In this case
> you wouldn't be able to make SSS ignoring reflected light.
> What's the real-life example of such a setup you're trying to achieve?
> (assuming Cycles is more or less physical based your setup seems a bit
> weird :)
> On Sat, Jan 17, 2015 at 6:51 PM, Greg Zaal <gregzzmail at gmail.com> wrote:
>> Hey folks :)
>> Is it possible to have a Ray Visibility switch for SSS, and possibly an
>> "Is SSS ray" output for the light path node too? Or possibly just combine
>> it with the Diffuse ray.
>> Why would this help?
>>    - At the moment it's impossible to have a light that only influences
>>    glossy rays - artists sometimes like to control their specular highlights
>>    separately (e.g. make them more prominent in the eyes) without affecting
>>    the rest of the lighting. If you have no SSS shaders, you can just disable
>>    everything except glossy in the Ray Visibility panel - but if you do have
>>    some SSS, it is doomed to be lit as well.
>>    See here: http://i.imgur.com/n2bNWvp.png - one red light underneath
>>    that influences everything, and one blue light above that's only supposed
>>    to influence glossy (sphere materials left to right: diffuse, glossy,
>>    glass, SSS)
>>    - I wrote a light manager add-on that is able to "turn off" the World
>>    lighting temporarily by disabling all the Ray Visibility switches. Sure
>>    this is a hacky solution, but it's more reliable than fiddling with the
>>    nodes.
>> So yeah - is this even possible? And if so, who I do I have to buy beer
>> for to make it happen? :)
>> Cheers,
>> Greg
>> _______________________________________________
>> Bf-cycles mailing list
>> Bf-cycles at blender.org
>> http://lists.blender.org/mailman/listinfo/bf-cycles
> --
> With best regards, Sergey Sharybin
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