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@KurzonDax : The veins are really only visible with strong backlighting, so will probably require a separete shader setup for that stiuation.
no - that one would be a easy map in translucency (and opacity)... that's how you bring every plant and lids to "alive" looking.. the veins are important.. because in a BUNCH of grapes/lids some will have backlight.
And you want the grapes looking sligthly different from each other (important for photorealism)..
Good point.
Here is a link with some intentionally heavy backlit grapes that shows the vein patter very well.
https://graphics.stanford.edu/courses/cs348b-competition/cs348b-03/grapes/
refraction is 1.37? ... i simply guessed it is between water and skin and set it to 1.38
...
Thinking about the rough, grey film.... could be possible to make that with flakes and bump... alpha mapped...... (just thinking loud)
I arrived at the 1.37 IOR based off of several articles about grape juice and wine. I could not find an examined value for just the grape.
checked the link - great resource - and they use VERY RIPE grapes .. i used a image which shows them still hanging on the vine branch..
?
need to find a good free grape bunch mesh.... something around/recommended? - i dont want buy or model one just for the sake of learning iray
The one I'm using is a free model I found using yobi3d.com. It's in MAX format though. I used a trial version of 3ds Max to export it to OBJ. The OBJ didn't import completely cleanly though. Specifically, the creator had some tiny leaves on the stem that didn't come in very well, so I deleted them. I'm using a cleaned up version of the diffuse maps that comes with it.
http://www.cadnav.com/3d-models/model-16621.html
the hardest test for grape renders is how do they look in snow and overcast sky
...
First very dissapointed because it looks now more like a olive to me.. i found this imag as reference... there is hope my setting are not so much off
Sorry to ask this, as I'm sure it's been covered but you guys just keep going and the thread's a little hard to keep up with when you have life, work and projects going on.... Is there a way to make skin look a bit more life like and translucent?
Been working on my normal maps for my skin I'm making for Dawn. Getting to where I'm liking it, mostly but still looks a bit flat to me and I really love when I see images where things are set up to give that "light playing off of peach fuzz" look if that's possible at all...
Don't get rid of that...when I get these done, you can use that for them...
well - Our grapes: what looks like a side project in the wrong thread - is actually very helpfull to answer exactly your question... a grape is difficult because it has it all - base - translucency, scatter, backscatter... same as skin.... But bringing all the parameters in a good looking balance which works also under different light - is difficult!..
Same for your render... it starts with the base texture.. when i tell you MY way... then you must start with overworking your base color texture....
It is way more easy to give you suggestions when you post your settings AND a screenshoot crop from your basetexture (it's not allowed to post your whole texture in the forum - when it is copyrighted)
@mjc1016 ahh.. there are the olives
,,,
I see you fighting the same challenge as i do right now... how do your fruits render in easy, sunlight?
I actually had to look up what "derogatory" means...
I'd prefer "rant", though. Which it actually was, I simply lost it. 
TRANSMITTED COLOR
The "Transmitted Color" property of the Volume Group is a parameter to simulate the absorption capability of our material, skin. How Iray does it I explained here in detail. The major part of that information comes directly from the very kind and helpful NVIDIA employees at the NVIDIA Advanced Rendering Forums. DAZ uses a set of values of RGB 1.0, 0.339223, 0.339223 on the Transmitted Color. A qoute:
"1.0 for the absorption color channel I would not recommend to use. As you said that means no absorption for red and is not very natural looking. ... in general i think its good to avoid 0's and 1's. Not only for absorption but also for reflectivities.
... having 0 or 1 in one of the channels of the volumes color will effectively disable any distance based change for this channel and make the material look slightly odd. For large distances it will look red and not change anymore if the thickness changes."
Earlier on this thread I posted a set of measured values and ranges of the minimum and maximum absorption coefficients I picked from
OPTICAL PROPERTIES OF HUMAN SKIN, SUBCUTANEOUS AND MUSCOUS TISSUES IN THE WAVELENGTH RANGE FROM 400 TO 2000 NM
A. N. BASHKATOV, E. A. GENINA, V. I. KOCHUBEY and V. V. TUCHIN
Journal of Physics D: Applied Physics
Volume 38, Issue 15 (2005) 2543-2555
INSTITUTE OF PHYSICS PUBLISHING
DOI: 10.1088/0022-3727/38/15/004
OPTICAL PROPERTIES OF SKIN, SUBCUTANEOUS AND MUSCLE TISSUES: A REVIEW
ALEXEY N. BASHKATOV, ELINA A. GENINA, and VALERY V. TUCHIN, J.
Journal of Innovative Optical Health Sciences
Vol. 4, No. 1 (2011) 9-38
World Scientific Publishing Company
DOI: 10.1142/S1793545811001319
[These are excellent reasearch papers, 'cause they cover the complete wavelength range of the visible light spectrum. Most you'll find will unfortunately lack the lower spectra of blue and/or even green.]
There are now several methods used/recommended to set the Transmitted Color:
DAZ uses RGB 1.0, 0.339223, 0.339223 on every Generation 7 figure... and we already found out why that set of values is completely nonsense.
InaneGlory uses RGB 0.464741, 0.21952, 0.121986 with a Measurement Distance of 10.0 on her "IG Iray Essentials" product. That will put the absorption coefficents a bit of of the range of measured values. At a tenth of those. I yet have to take a look on the recently published Gia, Aiko and Stephanie shaders.
@MEC4D suggests to pick it in Photoshop directly from the original diffuse texture: [quote] "you choose the color for Transmission by seeing the exactly level of Luminosity, what is the L in color picker. Forehead is a good place to pick up the color, should be not less than 56 and not greater than 72 ... around 68 is the best for Caucasian skin." [end quote]. But this will only work more or less properly in conjunction with the de-vibrance method of the diffuse textures and that "bloody dermis" simulating translucency.
What would work IMO best to get a realistically simulated skin would be a method similar to that: a greyish albedo texture to mimic a bloodless skin, a Transmitted Color to add the melanin coloring effect of the epidermis, and a translucency color which simulates the "bloody dermis" viewed through the relatively bloodless epidermis.
GLOSSINESS
Yes, I treat the body different from the skin. Most of the glossiness on a face is a result of different sebum concentration (the so-called T-zone), making nose, forehead, cheeks and chin more shiny than the "dryer" less sebum covered parts. I'm currently reading through a reaserch paper (titled Lipid Studies on the Human Skin Surface by Means of the Monomolecular Layer Method) which includes a nice graphic about the "Average spreading index of lipids" to see if it could be used to create a GlossMap based on sebum concentration to determine the more glossy areas.
BEAUTIFUL SKIN SPECULAR MAP
Yes... to me not... could be used as GlossMap (RoughMap when inverted), but would need a bit overhaul, dark greys are too dark, light greys are not bright enough. They cover some areas of the T-zone, but leave off some important: nose ridge, nose tip, chin. The whole material preset is something else than Physically Based Shading. I argue years of 3Delight experience ported 1:1 over to Iray.
Yes, a thing similar to that belongs in the "Glossines" texture slot. Putting that into "Glossy Color" makes the same sense like putting a common Specular Map into "Weight" or tryin to put a square peg through a round hole: NONE!
Because:
Specular Reflectance from Skin Is White
The tissue cells and oil in the outermost layer of skin are dielectric materials that reflect light without coloring it (whereas metals such as gold color the light that is reflected due to highly varying indices of refraction over visible wavelengths of light.) Thus, a physically based skin shader should use a white specular color. In other words, the specular reflection of a white light from skin will be white, and the specular reflection of a colored light will be the same color as that light—regardless of the color of the underlying skin...
GPU Gems 3 "Chapter 14. Advanced Techniques for Realistic Real-Time Skin Rendering"
They've been moved down deeper in the 'WIP' pile...so that was the only render I did of them, for right now. When I have other things cleared out of the way I'll get back to them.
Actually, the Volume Group (SSS) of the Iray Uber manages Transmission (absorption determined through "Transmitted Color") and Scattering (diffusion, change of direction of the lightbeams) which currently is restricted to monochrome. Scattering itself doens't manage any coloring, just putting the lightbeams on a different travel route.
Had a similar idea and asked at NVIDIA, the map would have to be put into the "Transmitted Color" texture slot, but although there's one on the Iray Uber, unfortunately it wouldn`t work there, 'cause transmission can't be mapped at all in Iray. Sh...
@Arnold C.
Great conclusion....
"What would work IMO best to get a realistically simulated skin would be a method similar to that: a greyish albedo texture to mimic a bloodless skin, a Transmitted Color to add the melanin coloring effect of the epidermis, and a translucency color which simulates the "bloody dermis" viewed through the relatively bloodless epidermis."
There is just one problem..... I did TONS of tests with greyish textures... it does not look real because to much color details getting lost...the colors which should be scattered should come from SSS (full spectrum)... and not from translucency... this is the limited iray...
and that's why i leave a part of SSS including red in the albedo..... and here comes the LUMINACE into play...
One of the mainproblems off to hard looking skin in iray.. is that to many full vibrant colors in all channels getting mixed and end in a to "hard look or Painted Plastic look"....
That's why the Albedo Texture in Base should only use a NARROW range of red's, green, and blue... and translucency should bring the lower range of blue and green which are missed in the Albedo (doing so in setting a "BROWN" color as translucence....(actually how it is in nature)..
It has also to do with color mixing knowledge .. i am used to think in CMYB or HSB because i worked long in this sector...(pre-print, photo, cad)..
the transmitted color (unfortunately not of great use for "real deepnes of skin" look - can only be used to give the final TOUCH - the end tone of the final render... we can use it to correct the final Luminance and K/B (black)
Thank you, Arnold C! That was very illuminating. How did we not know that transmitted color was absorption? WTH! I've been at it backwards, no wonder it didn't make any damn sense.
with a full colorspectrum and mapable transmission and SSS... we would not need translucency.
And that's how full phyiscally based humand render models do it.
And then the base texture is only grey.
And the SSS map looks more or less like a normal diffuse map token from a photo whitout specular,,, because the absorbation color info of the different colors is actually well.. what we see on a photo of skin
translucency is a "cheat" parameter - using IOR 0 - based on the mesh thickness and light amount/direction...
we need it because we have a very limited SSS.. and that's why the whole disscusion about full red or not is laughable...
Actually - a correcter model would use refraction weight and color also for skin - but well... translucency is a old parameter... since 30 years in renders
we can paint a part of the red in the diffuse OR in translucency.... dosent matter! as long as the light trough ears and nose shines yellowish till red.. everything is fine.
we will just have problems using full 100% red when we try to make a very pale skin - that's the only difference....the only way then is to lower translucency to reduce the red.. which is the same as NOT having a full red from beginning.
The rest has to do with color mixing - dont oversaturate! and balancing the layers and luminance and to a lesser extend what skin really is.
That is what I menioned long time ago, and asked for the map option under the channel in place of just a color what would help a lot better than just picking middle color .
"We" did know and so DAZ, for that reason they used the bluish color to absorb the redness from the diffuse maps when it overpowered everything .
No it is not a difference with very pale skin, the issue with very pale skin is that the diffuse have too much brightness , if your diffuse skin maps are over exposed it will screw all other settings and the result will be out of balance , no matter tan or pale skin you need to keep the brightness "Luminosity "' in the same range as it will affect the Transulency channel
People with pale skin don't have less red blood color than other right? LOL
Cath I respect you enormously, but blue is not an absorption color. And DAZ did not use blue in the transmitted color, all of the Daz materials have had a pink there. They put a blue in the Translucency Reflectance Tint. Putting an absorption color in transmitted is making a huge difference especially on tanned skins like Gianni who is one of my favorites but is very hard to work with.
I'm not an entirely sure that your analysis of the neglibility of translucence is accurate, and here I am referring the the physical effect. If skin was not transclucent, there would be no SSS. How could there be? So I feel that any physically accurate model would require translucence. I can only assume, based on the evidence in front of me, that your analysis of how translucency is modeled is accurate, but I agree it ought to incorporate IOR to be accurate.
I don't know how Cath configures skin shaders, since I only own her metal and unshaven products (which are amazingly awesome). However, the real problem with Daz figures is that the red component in the transmitted color channel was set to 1 which equates to zero absorption. To offset all of the red, they (and other PAs) lowered the red (and some of the green) component in the SSS Reflectance Tint, resulting in the overall blueish color of the tint. Based on the fact that they have that 1 value in there for red, and the fact that we've often seen the transmitted distance value set to 10(!), it seems there was a general misunderstanding of how transmitted color worked, myself included.
Based purely on my casual observations, I'm pretty sure SSS doesn't even get applied unless translucency is >0.
My observation as well. Thats down to how they built the shader, but...I think they are correct (regardless of any other mistakes there may be).
Using this "color" correctly opens up a whole new world it seems.
Agreed. Once I accurately understood the way transmitted color is used, thanks to @Arnold C., it made a huge difference in realism of my skin shaders.
KurzonDax
Because translucency IS allready included in scattering and refraction... (just limited to one color in Iray...
Look on a glas or water shader -> translucency is set to zero.
a material with refraction weight.. IS tranclucent... if you use BOTH parmateters (translucent AND refraction weight - IRAY does some strange things....
Here is a example: look on the shadow! translucency is a simplification (cheating refraction weight using a IOR 0) of refraction !..
All I did was try these settings that were posted on a previous page. I'm way behind on learning iRay because of health issues this past year but trying to get enough crammed into my head to get this product finished up...
Does IOR include translucence or opacity? I just checked the glass I am rendering on a chandelier and 100 percent IOR gives transparency.