Why not b/w translucency and SSS maps?
SnowSultan
Posts: 3,641
Skin often looks really good right out of the box with many textures sold here, but can someone explain the reasons why we don't use hand-made grayscale SSS or translucency maps? They're always just lighter versions of the diffuse texture, and to be honest, I'm not really sure *why* they work well. Why not use something that looks like an opacity map, with thin areas of the body (ears, between fingers, parts of face, etc) colored lighter and ones where light would not shine through colored darker? Does it have something to do with how Studio handles subsurface scattering? The fact that fingers can sometimes appear almost gelatin-like in front of bright lighting (and they shouldn't be THAT translucent) just makes me wonder if our current way is the only way. Thanks in advance.
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The gelatin like fingers, noses, etc is probably from people using incorect settings. I can only speak for myself, but I dont have this problem at all in octane, and I never use any sort of sss map. I assume iray should be capable of the same thing.
Possibly, but doesn't Octane have a far more complex material system? Regardless, I've seen professionals use the kind of translucency and SSS maps that I'm describing in programs like Maya, which is why I'm wondering if there is a specific reason why we don't use them in Studio.
As I understand it, the strength slots are generally tuned tor B/W-grayscale maps, and the color slots are tuned for color maps. If you try putting a B/W map into the translucency color slot with current Iray settings, the character will wash out very badly. I actually do use B/W maps in the strength slots for darker skinned characters, to mute the effect of translucency on palms and soles.
Right, but why do we need a translucency color map to begin with? I doubt there are that many areas on the human body where the skin and internal coloring would be different enough to require an additional albedo map. Maybe I don't quite understand what translucency is affecting in Iray, because *why* this works is still a bit of a mystery to me.
I'm not complaining about the results or even the method, I'd just like to know why we don't have to create separate maps to indicate where SSS and translucent areas of the body should be. To me, it would seem like we would need to do it the same way we define glossy/roughness or metallicity.
When I look down on my hands I very much notice the blue of my veins.
I do too, but that would be shown on the diffuse/albedo map. Does anyone understand what I'm talking about here?
For more realistic textures you do not add alot of colour to the diffuse layer, it is added moreso on the trasnlucency maps.
Personally I balance it out more with some colour details on the diffuse and some other details (veins and tones, etc) on the translucency maps. This can give quite a depth to the tonal range of skin...here is what I did for and upcoming character
You can see how many tones and skin details there actually are when you use the different maps.
some figures have them, I have too many to search but at least one has veins on a separate map and another has SSS maps
https://www.daz3d.com/sisi-for-genesis-8-female
and Syph no longer at this store
I tune my translucency to 1.0 and use a diffuse map as the translucency map, I don't even use the diffuse channel at all! <= Well, that's not true, as I use them for the viewport!
Almost every texture I own uses a lighter version of the diffuse map as its translucency map though, and none of them have b/w maps indicating where the translucency should be strongest or less prominent. That's what I'm not understanding here.
I think we got a handful of them in the late days of G3 textures, but it didn't seem to do a whole lot to improve realism then. Nowadays, the skin textures look much better.
That is...unique. :)
B/W would be used to adjust translucency weights, which is different than translucency colour. Translucency weight can be used to create certian effects, but it is not as intuitive as you would hope it would be. It works more like skin being less translucent (showing less skin undertones) like an elbow, as opposed to the palms of your hand which tend to be more translucent, showing alot more undertone. Yes you can use the weight to affect that, but it is easier just to paint more or less detail into the transclucency colour and just have a static percentage dialed in across the character. It also make the resources lighter in not having to call in extra maps which will slow things down.
There are many ways to achieve effects in d/s....its all about finding the best and most efficient
Another factor is that darker color in Translucency Color lowers effective translucency, so having a detailed weight map TOO is redundant.
Shaders in Octane are simpler, easier to understand, and easily accessible for you to work with. They are also way way way faster to modify and test compared to Iray. (Redoing all the shaders in a scene from Iray to Octane is incredibly time consuming. If you use lots of different stuff, then its not a great option.)
Skin is another matter, and not simple at all... I tried to build my own shader.. and I gave up. Redspec Skin shaders are a must have item for Octane, and they work exactly like you are discussing. Using the shaders themselves tends to produce very very very consistent results even with the worst materials to start with. They just work. Dark skins are a problem for RedSpec, and you just have to tone down the SSS.
IMO the real concern here is that many of the shaders for products in Iray are so tuned to Iray, that any update in the future may literally destroy the use of those shaders. Some vendors have even tuned skin textures to the shader and not the other way around. (You will see seams when you use the textures outside of Iray.) I'm often left wondering why they changed things like Iray tone mapping, and gamma to get their results.. because you can't always do that in a scene. Overall, there's not a lot of consistency.
The real question for vendors\artists, is how much they need the SSS skin details like veins. How much realism is all that really adding to your scenes? I don't personally see it as being that important. I've only done a few closeups which could really show that.
Check out MelisaGT post about making an awesome skin tweak for iray Shader.
https://www.daz3d.com/forums/discussion/526396/my-skin-tweaks-for-the-iray-uber-shader/p1
I also agree that RedSpec shaders for Octane is a must have. The Skin sjhaders included in the ORK are very good starting point also,
https://www.daz3d.com/octane-render-kit
So I did a test where I render a DO character in Octane with my own shader, one without the sss map and one with. In this case I used Torment 8.1. Can you spot the difference? If not I dont blame you, the difference is very subtle. I can kind of see where the one that uses the SSS map makes the red tones pop slightly more. In this use case, I definitely dont think it's worth having, cosnidering that it's another map to hog up vram.
Thank you for the replies and explanations.
Yes, it is but I use the specular rendering setting exclusively, and you need to bump up the translucency for it to be viable but the trick is to also set transmission to 254/254/254 so the textures don't cause green texture seams to show if you keep the default color for the transmission, I'll post some examples later.
EDIT: I pretty much used this tutorial as a base for my own shaders...