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Diffuse Strength + SSS Strength = 100%?
Posted: 02 May 2013 02:43 PM   [ Ignore ]
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Okay… so I was just told that Diffuse and SubSurface Strength on any shader in 3DL should always add up to 100% for it to work as it is supposed to…

Is this true?  I’m looking at a render of Bree, the only thing I changed was dialing down the diffuse to 50% (because the SSS was at 50% in the default…) and I’m a little… unclear as to why I would be told this…

Oh, I only did it to the skin, Lips through Toenails..

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Posted: 02 May 2013 02:57 PM   [ Ignore ]   [ # 1 ]
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Well, there’s the idea that if you are trying to be physically correct, or even plausible, the outgoing light (specularity+diffuse+SSS) should not exceed the incoming light, which would be the case if their strengths added up to 100% (or even a bit less, since some light is lost - absorbed and remitted as heat).

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Posted: 02 May 2013 03:04 PM   [ Ignore ]   [ # 2 ]
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It is a new one on me but I use SSS strength maps so I always have it on 100% and Diffuse on 80%.

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Posted: 02 May 2013 03:06 PM   [ Ignore ]   [ # 3 ]
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The math is beginning to make my head spin… unless it’s not based on incoming light and only based on what’s reflected… So If I set everything at 33.3, Diff, Spec and SSS I would be “correct?”

Let me just add this: I have never seen light coming through the ear the way I see on some renders.  I don’t know how to even get that…

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Posted: 02 May 2013 03:35 PM   [ Ignore ]   [ # 4 ]
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There’s often more SSS than is strictly realistic, which can produce excessive light coming from unexpected places (as can not having sahdows on on lights with Translucence on).

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Posted: 02 May 2013 06:43 PM   [ Ignore ]   [ # 5 ]
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people is obsessed with SSS since the eons of times…in real world is a minimal parameter when many others values do more for a realistic skin.
in MaxwellRendes I saw about 3-4 skin maps like dermal, subdermal, oil map…OIL MAP???

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Posted: 02 May 2013 06:57 PM   [ Ignore ]   [ # 6 ]
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ZilverG, I know! I know… what you say is true.  It’s just that those guys using Firefly have lorded it over us so long… I wanna SHOW THEM! raspberry

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Posted: 02 May 2013 09:39 PM   [ Ignore ]   [ # 7 ]
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wancow - 02 May 2013 06:57 PM

ZilverG, I know! I know… what you say is true.  It’s just that those guys using Firefly have lorded it over us so long… I wanna SHOW THEM! raspberry

It’s harder to get that glowy-eared translucent plastic kewpie doll look in 3Delight, but if that’s what you’re going for, crank the velvet up to 100% and set it to a medium tone on top of everything else.


I don’t think SSS should approach or exceed diffuse.  When I try to render with skins with settings like this they look unnaturally luminous and don’t seem to react to scene lights, and if I’m not creating a supernatural character, that’s not usually what I want.

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Posted: 03 May 2013 06:29 AM   [ Ignore ]   [ # 8 ]
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Due tothe physical law of Conservation of Energy, (diffuse+specular+sss ) = 100% total. Bowing to richard, SSS ought to take the absorption into effect.

This ain’t the real world.

Would it be nice if the shader, somewhere, took this into account and did the balance for us? Yes.

Are the results accurate? Well, no not really.

SSS is actually a much larger part of the visual appearance of many things, human skin being a particular example of where it is very important.  Diffuse reflectance is actually pretty damn low on the percentage of what we actually see.  But what we have here in Studio and other renderers is not a physically accurate representation: its a best guess, an approximation, a replica.

This is also ART.  Some of it really OUGHT to be up to the eye of the artist, attempts at photo realism somewhat to the side.

Until Studio has a shader like ezSkin (yes, I know, its not a shader per se; but you know what it does have: conservation of energy built in, or at least an approximation there of), Studio is going to be more on the artistic interpretation side and less on the realism side.

And I’m not dissing Studio, you’ll find me in the Studio forums over the Poser forums 9 times out of 10.  These are simple facts.

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Posted: 03 May 2013 06:33 AM   [ Ignore ]   [ # 9 ]
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wancow - 02 May 2013 03:06 PM

The math is beginning to make my head spin… unless it’s not based on incoming light and only based on what’s reflected… So If I set everything at 33.3, Diff, Spec and SSS I would be “correct?”

Let me just add this: I have never seen light coming through the ear the way I see on some renders.  I don’t know how to even get that…

No, that would not be correct.

To be “correct” your diffuse would need to be way down (this number 0f 6% sticks in my head from something i read, but I may be wrong), with specular somewhere above that and the majority of it coming from SSS.

If you use the US2 shader, you might be able to get some backscatter, I have not tested it; but there is a backscatter boost built in.  I find it unlikely that you are going to see much backscatter with other shaders without a serious sss map (and I don’t it even then).

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Posted: 03 May 2013 06:38 AM   [ Ignore ]   [ # 10 ]
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zilvergrafix - 02 May 2013 06:43 PM

people is obsessed with SSS since the eons of times…in real world is a minimal parameter when many others values do more for a realistic skin.
in MaxwellRendes I saw about 3-4 skin maps like dermal, subdermal, oil map…OIL MAP???

That’s not quite accurate.  SSS is the PRIMARY factor in what you see when you look at human skin.  Diffuse reflectance and specularity are minimal in comparison.

in your brief mention of these maps… well yes, to be truly accurate you are going to need all of those and probably more, and all of those that you mention would be involved in sss calculations: oil would apply more to specularity, but if its reflected by the oil is not going to penetrate and scatter, the dermis is going to absorb some and reflect some and some will penetrate (we are talking about light here) and the same with subdermal (though this is where a lot of the scattering happens).


I have begun to truly realize what an awesome process this is, and it does not surprise me in the least that we are not able to simulate it casually.

 

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Posted: 03 May 2013 06:47 AM   [ Ignore ]   [ # 11 ]
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oh, and you NEED global illumination of some kind or a ton of lights (which is not as accurate or desirable IMO).

And when you start adding in the various control maps, you’re “Accurate” percentages go out the window.

Fudge it.  Use light tricks.  Use all the tools in your arsenal, because its a COMPLEX process that changes in an eyeblink…. so just do your best, and satisfy your own eyes.

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Posted: 03 May 2013 07:39 AM   [ Ignore ]   [ # 12 ]
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evilded777 - 03 May 2013 06:38 AM

.. SSS is the PRIMARY factor in what you see when you look at human skin.  Diffuse reflectance and specularity are minimal in comparison.

The top layers of skin are almost totally transparent, think of when one peals skin away. If one were to try to mimic reality they would put the ‘Diffuse Map’ in the SSS channel and have a semi opaque setting in the diffuse it would seem. I’ve seen some skin textures where they do this. I’ve played with doing this on various materials but haven’t done enough yet to put up any conclusions, other then at times it gives the exact same results putting the diffuse map in diffuse or sss. So, I’m guessing the differences come with lighting and various settings I haven’t worked out all of the details on yet.

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Posted: 03 May 2013 08:09 AM   [ Ignore ]   [ # 13 ]
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I always render with a map in the SSS Chanel, most often the diffuse map because I’m too lazy to create custom SSS maps… however, most of what’s been said here I really didn’t know or had never thought of.

Thank you Evilded, you really shed quite a bit of “Light” on the situation for me.  You jacked up the intensity!  You turned off the damn limits! raspberry

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Posted: 03 May 2013 11:28 AM   [ Ignore ]   [ # 14 ]
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evilded777 - 03 May 2013 06:38 AM
zilvergrafix - 02 May 2013 06:43 PM

people is obsessed with SSS since the eons of times…in real world is a minimal parameter when many others values do more for a realistic skin.
in MaxwellRendes I saw about 3-4 skin maps like dermal, subdermal, oil map…OIL MAP???

That’s not quite accurate.  SSS is the PRIMARY factor in what you see when you look at human skin.  Diffuse reflectance and specularity are minimal in comparison.

in your brief mention of these maps… well yes, to be truly accurate you are going to need all of those and probably more, and all of those that you mention would be involved in sss calculations: oil would apply more to specularity, but if its reflected by the oil is not going to penetrate and scatter, the dermis is going to absorb some and reflect some and some will penetrate (we are talking about light here) and the same with subdermal (though this is where a lot of the scattering happens).


I have begun to truly realize what an awesome process this is, and it does not surprise me in the least that we are not able to simulate it casually.

Hmm.  I wonder if geometry shells fit “tight” enough to simulate an epidermis?  Probably not, but it might be worth trying.  Most of the time I just don’t think about the biology because it’s so irrelevant to how models are built and rendered (we are very squishy, complicated creatures compared to these!).

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Posted: 03 May 2013 11:42 AM   [ Ignore ]   [ # 15 ]
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SickleYield - 03 May 2013 11:28 AM

Hmm.  I wonder if geometry shells fit “tight” enough to simulate an epidermis?  Probably not, but it might be worth trying.  Most of the time I just don’t think about the biology because it’s so irrelevant to how models are built and rendered (we are very squishy, complicated creatures compared to these!).

You know that thought occurred to me too… experiments might be revealing…

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