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DAZ uber iray diffuse translucency ,three "Base color effect" options

waitinfuture

Inspired
Hi, I have serched and tried to find how actually , DAZ uber iray , Bse>Diffuse>translucency>base color effect , option work. (as clear RGB value, which will be used as final translucency color)

As you know, this option is important, because iray use "translucency color " as Filter for SSS effect first.
then with "base color effect" option, it change how circluate SSS effect too.

But I can not still find, how it is circulated. I can only try and test then see shader generate effect, but really hope to know clear formula, what RGB will be send for SSS effect. (or what is final translucency color,
after base color effect.

I can easy find, when Base color is "scatter only", Base color have no effect about translucency.
but the problem are, when I set Base color effect as

1. "scatter and transmit"
2 "scatter and transmit weight"

I have read many times, the section of DAZ uber iray document. then can understand abstractly how each option work. but to easy set SSS what I planed, I really hope to know, how "base color effect options" decide, translucency color which send to second layer as SSS base color as mathmatics formula. of (RGB)

Please teach or help me , if someone already found or asked DAZ then get answer, how base color (RGB)
circulate for addtional translucency color , with transulucency weight value, about case 2 and case 3.
then hope to find stable formula.

final translucency color = f(base color, translucency weight, translucency color)

I know already, we can ignore "reflactant SSS tint", it is just for modify old iray shader mat
it just be multipled for "Base color" then the multipled color are used for real "base color"
about this case, I keep it as "perfect white", that means, reflecant tint SSS have no effect about "base color"
and function, what I hope to find.

The reason why I hope to find clear formula, with each value of shader, I have tried to help ,
Thomas Larson DAZ import plug-in improvement. who offer "cool blender plug in" for daz studio contents.

Diffeomorphic: DAZ Importer version 1.2
Diffeomorphic / Import DAZ — Bitbucket

It is really enhanced already, it can import rig , most of mat and texture for blender.
then at current, he keep trying to convert daz iray mat, for blender cycles node,
mainly use principled BSDF to get more reliable PBR material.

it have been improved, but As you know, cycles and iray is clear different render,and shader differently work.
then we may need to convert and get aproximately same mat produced by cycles and textures which we used for daz iray mat.

glossy or metalness thing is not so difficult, but about refraction, translucency, and SSS we need more tweaking. because DAZ made uber iray shader with many option.
I can almost found how refraction thigns work, (though it is not so simple to covnert for principled bsdf)
But the translucency color and SSS parmeters effect much for figure skin. (it is purpose we use this plug-in for blender), then hope to produce most relibable stable converion manner.

I am not professional for those shader things, then hope another daz studio users who have more mathmatic, and shader knowledge help me, or you can direct tell your knowledge to Thomas Rarson. to enhance his plug-in. he never asked me, to help his plug-in ,it is just what I hope to do. simply because,
I like blender, and hope to use daz contents with blender (and redner cycles)

Anyway, even though it is not for blender plug-in, Do not you simply hope to know, each base color effect option how circulate, and used for translucency and SSS effect? At least I hope to know, but unfortunately, I could not get answer from DAZ official about these things, it is out of their support things.
and I am not native speaker, and can not use daz formula anymore, for some my personal reason.

then I can only ask another daz users to help and teach me. (and it is not nvidia matter, because daz add those option for base color effect,,)

hope someone find this topic, and will offer answer . (though it is prediction, we can test, then if ti work well,
we can use the formula, as an approximation.
 

kobaltkween

Brilliant
Contributing Artist
Iray has SSS much like Luxrender's. It's really great for homogeneous, translucent media like glass, water, fog, etc. It's not so great for skin, plants, animals, or anything completely solid. Firefly and 3Delight both have BSRDF that's designed for skin and doesn't work for volumetric absorption. Cycles/Superfly has both. That said, I've found absolutely no way to make Cycles reproduce the _beautifully_ slightly translucent teeth I made in Iray.

I'm not sure a formula will be able to produce reliably similar results in Cycles, because Iray uses one type of scattering where Cycles more usably uses two. In Cycles, you don't want to use the same method for scattering in glass as you do in skin, a difference that's less about scattering settings and more about how all the settings come together. Also, I just discovered that Blender's SSS doesn't quite work properly when it's inside a refractor. I'm very sure that Iray, as a spectral renderer, has no such problems.

That said, if you're using Blender 2.79 or higher, any opaque material can be made with the new principled (PBR) shader node. I find it absolutely great for skin because it has a separate diffuse and SSS color. Because of that fact, the many different shading styles you can go for with skin, how vastly different those styles react to light, and how strongly skin tone affects scattering amount and color, I would strongly recommend taking the time to customize a skin shader using the Principled node. I would hope that the plugin converts most basic materials to just a texture or color and the PBR node. If it doesn't now, it probably will soon. And you can just set up materials really quickly by hand with it, as long as you have the textures.
 

phdubrov

Noteworthy
Contributing Artist
If you want the exact solution, look into the MDL Handbook (mdlhandbook.com) about glossy transmission and diffuse transmission and into the source of Ubershader in shaders/iray/daz_3d.
 

kobaltkween

Brilliant
Contributing Artist
Scattering volume inside refraction boundary or something else?
As far as I can tell, once the ray has gone through a refractor, something goes wrong so the scattering dims. If you have, say, a plain refraction node set to an IOR of 1 and white, it should be perfectly transparent. If part of your object with SSS (as a solo node or as part of a PBR node) is within or behind that refractor, it will be much darker.

I found this out testing out my eyeball for SculptJanuary's Monday challenge. Other use cases would be plants in water, people in water, etc. It's not the end of the world, and the darkening effect can be useful, but IMHO, it's a notable issue.

That said, you can get volumetric shading in Blender without exactly having a volume. If you make a pool and just make the water a plane, its volumetric shading works just fine.
 

waitinfuture

Inspired
I thanks about all replys about my question, but what I serch around is, the clear mathmatical value difference,
when I set "base color effect" as "scatter and transmit" , scatter and transmit weight, or "scatter only".

I know, blender SSS shader, and principled BSDF sss are differentl shader. then I can not perfect conversion as same as daz iray material.
but it is not main problem. because it is j for plug-in auto- conversion process. we expect, at least SSS color and texture show reasonable skin color,
as same as daz studio. not expect plug-in auto conversion which show pefectly same detail effect.

Actually if I manually tweak skin with cycles node with use vendor offer mat textures, it is not so hard.I already know, how cycles SSS work with node parameters.
and I understand, it can not re-produce, all effect, which iray volume shader offer.
(I already play with MDL handbook, or asked about SSS in nvidia MDL forum, then those shader and render difference is not matter what I asked about
daz iray shader option.

As phdublob said, yes I can learn about MDL , and how iray shader composit. but this option is not madd by nvidia. it is just added by DAZ developer, for their default iray shader
as daz manner. then I test with many values, with each option, but I still can not get how reminder color are sent as translucency color for iray diffuse transmisison BSDF.

Even though I can not convert all iray SSS effect by cycles shader, at least I can use translucent BSDF. of cycles. for iray diffuse transmission BSDF.
and daz uber iray> diffuse>"translucency color" is color value which used for, iray diffuse transmission BSDF.
But if I set base color effect option, as "scatter and transmit", the color which used for diffuse transmission change with base color.
then I hope to know, clear formula..

clear example is,
I remove all glossy reflection, reflaction value. then concentlate only about, diffuse reflection and transmision for uber iray shader.
I set shader property values (for diffuse) like that. I do not use thin wall, but not add any SSS effect.
so it only show diffuse refleciton and diffuse transmission shader effect of iray.

base color = 0.8, 0.8, 0.8 (this color will be send for diffuse reflection) (layer 1 )
translucency color = 0.7, 0.5, 0.3 (this color will be send for diffuse transmission shader,, ) (layer 2)
translucency weight = 0.2 (translucency layer are mixed by weight value, with Layer 2 (non transmisison base layer)

if base color effect "scatter only"
the weight value is used for mix base layer effect, for translucency layer.

So I can convert it for cycles without problem, I can use mix factor, for (base shader, and translucent shader), then it show same mat.
I can use same values for cycles principled bsdf, and cycles translucent shader .
(the translucency color is cycles translucent shader color, base color can use for principled bsdf base color, then just use mix shader).

it actually show almost same effect. and same mat.

My quesiton is,, when I set "scatter and transmit" for base color with uber iray shader,
the RGB values which may used for "iray diffuse translucency" and how mix value work.

there are only 4 parameter, now I need to take count in.

1. base color, 0.8, 0.8, 0.8
2. tarnslucency color 0.7, 0.5, 0.3
3 translucency weight,0.2
4 diffues effect otpion.

daz document discirbe, abstractly, "remidner color" is sent, but what forumla I use, I think I can not reproduce it
eg I thought, reminder rgb of base color = 0.2, 0.2 0.2
then it will be sent as addtional transmisison color, then final transmission color = (0.9, 0.7, 0.5)
then it will be mixed with base reflection layer, with layer weight.

it was wrong.

like that I tried with many assamption, (eg I multiple additional reminder color with translucency color, then added with transmission color etc)
but I can not still find, such simple value circulation (it should be simple enough,) and daz document never tell me, clearly.
I do not know, why daz need to hide, such formula, just base color effect option. and without those knowledge,
I think, we just mix shader value, without clear mathmatical manner, but with really abstract manner. even though it is for material which expected to
render with PBR manner.
 

waitinfuture

Inspired
Hi, thanks agentunawares, but unfortunately when I try it, those conversion are hidden as uber iray shader blick.
I can use shader mixer for use custom MDL, or re-produce, shader with MDL handbook by daz offer MDL blicks.
but about how uber iray shader cicrulate, with base color effect option, I feel I do not have way.

But I may re-try what you suggested, because when I tried to check node mixing way in shader mixer, I did not have enough knowledge, then just thought it is hidden.
if I can use, another node, to expand daz customize nodes, to check how it is cirulated.

(so I hope, if someone could find it, just dicribe it your assamption. or what you can see by reading code, etc.
I do not think, it need to be as secret. even though daz use additonal node, for mixing, it is just about, "how base color work for translucency"
as daz documet said. we only need, actually how it will be circulated.

I serched around about this in daz forum, but all things are just abstractly discribed. (eg I feel, the transmission effect more strong etc,,,)
yes I can see with same effect, but do not we need, to know, actually how RGB change for tarnslucency? it is base filter color for SSS.
we love SSS , then use for daz figure mat more real, why we do not know base filter color how set with daz offer option?
 

waitinfuture

Inspired
Unfotrunately all those shader properties about diffuse are included in one "PBR metaricity base" blick. it is not circulated out of this blick.

I can not check , how this blick are discribed as MDL. (I do not suppose, daz offer convert shader , which made in "shader mixer blicks" as MDL file which we can readable.
if this "PBR metaricity base" are offered by nvidia, then daz just re-use it, I may send letter nvidia, to teach me, only about my question. but I believe it is daz custom MDL blick.

I can save it as dbm , as user custom blcik, but it just record input values,, so I feel I have no way by sneaking shader mixer.
(and It may need not sneak as if I make mod ^^; I believe, ds user have right to know, how shader circulate color for main property values of default shader which used for daz prodcut mat,,

anyway, thanks Hive wire 3d forum members, to reply this topic, I really feel thanks. (and still hope if some daz user or just for quriosity, try same thing, and already found formula by test ,, please offer it here)
 

waitinfuture

Inspired
>phdubrov

thanks, now I read agaiin all reply, then I could find the MDL file of PBR metaricity base in my PC programs folda. I seems just believed it encrypted (before I felt so)
then I tried to serch file with name. it is not encrypted. So at least I can read this MDL. maybe it is not so difficult. if I could found clear how circulate.(I believe so)
I may up-load here, only about how base (RGB) circulated for translucency (RGB) with options.
thanks again!
 

kobaltkween

Brilliant
Contributing Artist
Um.... So no, there's not going to be a simple, consistent conversion because they're not the same shading phenomena at all.

Translucence, both in Iray and in Cycles, isn't designed for volumes. It's meant for single poly surfaces, like curtains and leaves. You shouldn't be using it for skin at all in either Iray or Cycles. I mean, you can manage to get good results doing that, but you're basically using a hammer as a screwdriver.

Iray SSS isn't equivalent to Cycles SSS, which is the same on its own or in the Princpled node. It's equivalent to Cycle's Volume Absorption or Volume Scatter. It's about as related to the SSS node as it is to the Diffuse node.

In my experience, there is no a consistent, texture and light independent mathematical relationship between Iray SSS and Blender SSS. You can probably find one between the volumetric nodes, but the SSS ones, not so much. Which isn't to say you can't just come up with a "makes decent skin given average lighting and average caucasian skin texture" setting that will work most of the time.
 
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waitinfuture

Inspired
>kobaltkween

When we use importer plug-in (of different renderengine and shader), we do not hope it offer perfect conversion, but hope reasonable conversion.
and plug in vendor just hope to offer best conversion. (of couse user hope it too), and usually hope to auto-set textures which offered (or we bought) for daz studio iray mat
with set reasonable value for cycles shader.

I think, at least we can use "translucency map" "translucency weight", and some proeprty values of iray volume and surface translucency, as same as base color map, metalness map, roughness map,,normal map etc.

About iray volume have those properties,
"ior" , "apsorption coefficient," "scatter coefficient," and volume shader, , df::anisotropic_vdf have, " directional_bias" as parameter.

As iray developer recommended, daz offer user parameters , which cicrulate "scatter coefficeint" and "absorption coefficeint" without we directly tweak those coefficient values.
but represent as "remaind color" with distance value, from transulucency layer surface.

Iray vdf can circluate, diffuse transmisson, and refraction as filter for absorption , scattering.

but blender SSS shader made only for diffuse transmisison, and scattering effect. if we hope to convert iray refraction, with volume absorption, scatter, (eg make smoke or god ray,, etc)
we need to mix use blender volume shader. (and it not means, both shader work same manner, parameter of shader, need to convert, or we can not use them)

But we do not need perfect conversion about all special materials. (We use daz figure, it is almost main purpose for daz studio, and main purpose of this plug in.
to use "daz figures" in blender without many customize . ,)

Then we can concentrate ,conversion of iray skin mat (without refraction, diffuse transmission (filter color send to volume for absorption, scattering) , volume absorption + scattering),
to more simple cycles (diffuse transmisison + scattering = cycles SSS) aproximately.

then , how "diffuse traslucency"color will be circulated and mix with "diffuse refraction " is base to convert iray mat skin for cycles mat. skin
even though we need to adjust SSS color and color RGB radius for cycles, from scratch. Actually before I do not hope plug-in offer SSS values for cycles.but
I simply hope to import translucency map, with correct weight values for cycles translucent shader.

At least, if plug-in can generate daz product "iray translucency map" and set "mixing weight" with correct value, for cycles SSS, It enhance importer.
(then user can start modify skin mat, with those map, and values witch plug-in convert aproximately) and can show more reasonable skin than,s
skin which just remove translucency and no use SSS.
 
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