JonnyRay's Tutorials

kitakoredaz

Thnaks I had read the new Post about SSS, then it teached me clear how scatter and absorb work .:lol:

Then, my curernt problem (and it is waht I hope to learn) is,, the Units of these Scatter and absorb value,
when I tweak parameter, Usually I clear understand each parameter units.
(eg % for strongneth, simply represent the value , or scale (cm), or frequency, or time etc)
But about the shader Scatter and absorb R,G,B value, I can not clear, what units they represents.

It cause me difficult to predict exactly and make the Susurface effected Color (untill layer with outer collor)
Though I can tweak each value Roughly and I can see the effect (calculated scatter and absorb R, G, B value with
subsurface color and strongneth,) after test render.

eg when I set one of absorb Color value to zero, the shader seems can not calculate.

it turn black. that means, maybe formula divide the value I think. (we can not use 0 for absorb value)
but actually , about some gem in real world, I know all red or green spectlum are almost absorbed. (not all)

About AOA subsurface shader, we may need to set absorb value at least more than zero?

like that,, I hope to know the units of scatter color value too.
Is it frequency how scatter each color value to the behind mesh?

if it is simply strongneth of scattered color, we may need not use scatter value I think,,
maybe we can get same effect, just change subsurface color,,, then fix scatter value of R,G,B.

I may need to serch more about Renia dodge too ^^; without it, I can not adjust and make surface color
which I hope to get with a few test. without prediction with clear knowledge, it make me uneasiness,,

JonnyRay

kitakoredaz said:

Thnaks I had read the new Post about SSS, then it teached me clear how scatter and absorb work .:lol:I'm happy it helped. I've updated the 2nd image to include the subsurface layer to show that the scattered light is assumed to be reflecting off the subsurface layer.

kitakoredaz said:

Then, my curernt problem (and it is waht I hope to learn) is,, the Units of these Scatter and absorb value,
when I tweak parameter, Usually I clear understand each parameter units.
(eg % for strongneth, simply represent the value , or scale (cm), or frequency, or time etc)
But about the shader Scatter and absorb R,G,B value, I can not clear, what units they represents.
As I understand it, the RGB value on Scatter is intended to indicate what part of the light spectrum gets scattered by the surface. This can be different than the underlying subsurface color. Think of it as "If the subsurface color is orange, but the scattering color is red, then the yellow part of the light gets filtered out".

It cause me difficult to predict exactly and make the Susurface effected Color (untill layer with outer collor)
Though I can tweak each value Roughly and I can see the effect (calculated scatter and absorb R, G, B value with
subsurface color and strongneth,) after test render.

eg when I set one of absorb Color value to zero, the shader seems can not calculate.

it turn black. that means, maybe formula divide the value I think. (we can not use 0 for absorb value)
but actually , about some gem in real world, I know all red or green spectlum are almost absorbed. (not all)

About AOA subsurface shader, we may need to set absorb value at least more than zero?

This one confuses me as I thought that the absorb should indicate what part of the light is removed; so a value of zero should mean that no light is removed. We may have to see if we can get info from Will on this one.

like that,, I hope to know the units of scatter color value too.
Is it frequency how scatter each color value to the behind mesh?

if it is simply strongneth of scattered color, we may need not use scatter value I think,,
maybe we can get same effect, just change subsurface color,,, then fix scatter value of R,G,B.One thing to consider with SSS enabled shaders is that you may need to adjust the surface strength values to conserve energy properly. So, if my SSS strength value is set to 20%, then my diffuse strength value should be reduced to 80%. If you're using the "velvet" setting, that should be calculated into the total as well. The end goal would be to get something close to 100% to be the "most realistic". However, also keep in mind that "realistic" does not necessarily mean "better". :)

mjc1016

JonnyRay said:

One thing to consider with SSS enabled shaders is that you may need to adjust the surface strength values to conserve energy properly. So, if my SSS strength value is set to 20%, then my diffuse strength value should be reduced to 80%. If you're using the "velvet" setting, that should be calculated into the total as well. The end goal would be to get something close to 100% to be the "most realistic". However, also keep in mind that "realistic" does not necessarily mean "better". :)

Can we get that bolded, highlighted, turned into a flashing neon banner?

kitakoredaz

Hi,, thank you,,, I may close to understand 70 % ^^;

As I understand it, the RGB value on Scatter is intended to . This can be different than the underlying subsurface color. Think of it as “If the subsurface color is orange, but the scattering color is red, then the yellow part of the light gets filtered out”.

Yes,, I can understand it. I think they are intended to change subsurface effect from same subsurface color.
can be option, to change Subsurface effect, from same subsurface color (or map),
and can change them.

But,,, If the each value of RGB simply represent , what part of color,

we may need simple Color picker style parameter, as same as diffuse or subsurface color, I think^^;
or simply represent about each R,G,B value, with parameter limits, R 0 to 255, or 0 to 1.00 ,,(100%)
about these case, I can tweak and decide the Scattered lay color easy,,, ^^;

about absorb color, limits is min 0 to max 1,
about scatter color , limits is min 0 to max 10.

So that I am little confuse,, if there is clear meaning , and these are not same units.
or it is same, about 0 to 100% ? (though we can not apply 0, as we checked already)

Then,, now I hope to know,,the correct reasonable way to adjust this shader^^;

that means, we may start better from subsurface color = white?
or we may start from subsurface color = black?

how we decide them? I know they should change with scatter, and absorb color already,

but eg, If I change shader about skin material which used by daz default shader,
to SSS, and hope to make sss translucency effect,

basically, at start point, we may set subsurface color with white,
then adjust each value?

Strictly speaking, if it is desigend , to apply sbusurface color map to get real subsurface effect for each human skin?
at start point? after that adjust Scatter R,G,B and absorb R,G,B ?
I think,, about Scatter R,G,B and absorb R,G,B,, it should be decided proximately for each material,,
as same as Reflaction index, so that there is preset eg SkinA and SkinB?

JonnyRay

I think the questions now are getting closer to how did Will (aka Age of Armour) implement these values in his shader. I'm not really qualified to answer those questions, though. :( It might be better for this to go back to your thread in Nuts-and-Bolts and see if we can get Will to offer some specific information there.

I'll ping him with a link to that thread and see if he can help.

Takeo.Kensei

AOA just used the SSS node from shader mixer which contains the presets from the Bssrdf paper from Jensen's Siggraph paper http://graphics.ucsd.edu/~henrik/papers/bssrdf/bssrdf.pdf

I never use AOA SSS but I guess the SSS colors/value/terms are done the same way as in Ubersurface ; you pick a SSS color from the sRGB space which is then translated to correct scattering and absorption. terms. You just pick the color you want to see as SSS. It is easier this way for end users

kitakoredaz

Thank you Jonny,, I am sorry, forget main subject of this toppic ^^;
I feel so interesting about this shader, and shaked my hand ,to understand from start point,(I really new comer about 3d basic
material things,,) ,,

Anyway, I decide to move my current question to my topic, and read the AoA kind guide,,to understand more clear ^^;
thank you Jonny,, kindly help me. and Takeo thanks.

(if some one join or advice or teach about AoA shader, , I apreciate , so that please write there.
http://www.daz3d.com/forums/discussion/37029/

Now My question is not how to make good artistic, or realistic render, I have not reached the point yet.
I simply need to know how to use and try this standard shader for new ds 4.6 correctly the way the AoA desigend :red:
I hope to use it as same as daz default shader,, ^^; not plan to study other shader, now,,

JonnyRay

I have added the following articles about subsurface scattering (SSS) to the OP.

Light and SSS Surfaces
SSS - Why Should I Care?
Additional Points about SSS

JonnyRay

I've just published Hair Rendering - Current State on my blog. There isn't a great deal of practical information there, but if anyone were curious about state-of-the-art hair shaders, I think I've gathered a bit of history and some links to some of the most important academic papers on the subject.

I was gathering this information for a hair shader that I'm working on for DAZ Studio. I figured since I had the notes anyway, I might as well share them. :)