Show Us Your Iray Renders. Part III
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Being a Daz PA. Could always just make your own.
Here's a link to the base Nvidia Iray logo http://images.nvidia.com/content/technologies/advanced-rendering/images/nvidia-iray/iray-logo.png
So true. I didn't count the amount of scientific papers about "The Optical Properties of Human Skin" I went through and instantly have trashed. Most of them overwhelm one with lots of equations, but lack to list even the relevant data to use in them. Only a handful is really useful for our cause.
There's a nice listing of refractive indexes available here: Sample dispersion & refractive index guide. It contains even some exotic materials like "Coffe Dust", "Ibuprofen" or "Insect Parts". :)
I would think the wax shader would work better then a car shader for hair. Hair has a large sss component.
...what about a skin shader as there is also a velvet quality??
OKnever mind, just read a later post and that won't work. The AoA SSS shaders do have a hair setting, may have to try that.
Perfect! that added just the pop I needed!
Thank you.
It working as well ..just with little translucent and look cool
Perfect! that added just the pop I needed!
Thank you.
I was working on ghost with the MDL shaders and ended with making fabric shader lol
no textures or bump maps all shader based .. cool what?
The fabrics look beautiful!
Thanks, now I wish I could bake it into my maps :( would be handy
here one more set with the shader
The outer layer of hair, like skin is translucent. The light goes through this translucent layer, made up of 'scales' and hits the melanin inside, what isn't absorbed by the melanin is bounced back out with a scatter effect. Do a google search on 'hair subsurface scatter' and you will find many results, including a pdf from Cornell University.
Those are beautiful. I am amazed you can get those from a procedural shader. It makes sense one should be able to, but It's first time I've seen something that involved in a procedural shader for fabric. :)
Don't understand, if you are getting this with a procedural shader, why would you want to bake it into maps? I try to move as much into procedural space as possible, away from maps. The trouble usually is that procedural tends to look too 'fake' (unlike these which look beautiful.) Less maps = less texture space.
Those are very impressive - I particularly like the inner dress in the first and the outer in the third.
Yes, equations are only really valuable if one is writing the underlying software, or perhaps some complicated nodes. For most of us, it's the principles that matter, not the details of the formulas. About the ior, it's not a single number... it's a curve that represents how the Fresnel acts. It needs falloff values that are different for different materials. A single number won't represent this. The only way I can see to represent the falloffs for different materials is as an equation (specific to the material) that defines the falloff curve. I believe that is one of the things people are trying to map right now in PBR for various materials.
Sort of...
IF you are dealing with a limited spectrum renderer (most are NOT full spectrum) then yes, the single value IoR is 'close enough'. You don't really gain much more realism using a full spectrum calculated one over the single one...but you do gain some calculating overhead (slower rendering). Those single IoR values should have a wavelength attached to them...somewhere, probably in the data tables all the charts are taken from (Engineering/Physics manuals/references). For most things, in the visible range of the spectrum, it's a pretty flat curve.
That's why a PBR that uses n-k files for metals can get spot on metals...that's what the n-k file IS...a tabulated data file of points on that curve. And yes, everything can be turned into that kind of data file...but the flatness of the curve for many things, within the visible part of the spectrum and especially at the wavelengths most renderers use, up until now, didn't require the effort to use that data (and a other than metals) there aren't many other things that have the data, in depth, already (some engineering references for various glasses do and some other strange items...like some concrete and ceramics).
You are referring specifically to Fresnel ior I assume? What I am referring to is similar to what the 'glossiness' did to specular highlights in 3Dlight in that the angle at which the Fresnel effect starts and the related sharpness of the Fresnel effect varies from surface to surface. The Fresnel curve for metal is flat for much of the curve of an object with it not kicking in until the angle reaches a certain point, at which point the effect is relatively sharp. With rubber, the Fresnel curve starts much earlier and is more gradual. This is visible in any render engine if it treats this correctly. As to there being a limited amount of that data available, yes, that's what I was referring to when I mentioned that people are actively mapping this now. It is an active part of the PBR materials libraries that are being put together by companies like Allegorithmic now.
We could dial in the Fresnel curve just like glossiness in 3Dlight but that would be guessing. One of the points of PBR is to nail down some of these aspects of materials so we have a 'correct' value for a given material (or as close as we can for our level of technology.) When we dial it in, we can get something that looks correct for a given lighting condition but if what we did is actually off axis, it will not map to different lighting.
My earlier point about Fresnel being one of the gems of PBR has to do with how the PBR movement has put focus on Fresnel in a way that wasn't there before and has therefore made people start giving this important aspect more consideration. All materials have some Fresnel, but many if not most never included a Fresnel component from what I've seen. I think a lot of people expected Specular to do the job of spec and Fresnel without ever realizing it. The next part of this however is realizing that Fresnel isn't just 'at the edge' of an object but rather extends around the curve of an edge to a greater or lesser extent depending on the material, and is sharper, less sharp at the edge also depending on the material (conservation of energy and all.)
Very cool stuff! I like the 3rd from top on "catalogue page" #517. And the 2nd. But they're all beautiful.
I tried my luck with cars now.
Guess why she's grinning? I bought her that fancy german luxury car from Stuttgart (modeled by Mysthero). :)
"Carpaint Blue" MDL Example, "HDR 111 Parking Lot" from HDRI-Hub.
I'm not sure which paper it is...I've so darn many of them saved...but basically, they are connected. Get the correct full spectrum data and the right roughness values and the rest SHOULD take care of itself...if the surface models are accurate. But, yes, if you aren't using a full measured data, data file you do need to do what Allegorithmic is doing...basically turning that uber-geek stuff into Artist friendly ways of getting to the same place.
Ok, I get what you are referring to now. My point was that they use that data to generate the curves, or at least that is my understanding.
Ahh, that was what I was forgetting.. roughness. You are correct, a single value ior combined with a proper roughness value should give one the curve for a given material, or at least close enough. Too bad roughness is such a hog for render time, at least when combined with translucency, reflection, etc... (We need more power Scotty!) ;)
As to the full spectrum data, I'm assuming (perhaps incorrectly) that if measurements are taken under a full spectrum light source, that the render engine should be able to derive what the values should be under varying spectral lighting environments.
Looking pretty good there Pearbear!
Now you're just showing off :coolgrin: LOL I KEED I KEEED!
They looks wonderful & I'll bet it renders fairly fast too? All ready for the Met Gala. Time to werk the runway!
Those fabrics look really nice, MEC4D.
Thanks Alex! In trying to fit three figures in while cropping out the head of one due to a lack of "lying down" hair morphs I realize that the composition is very bizarre looking and kinda unsettling. Maybe like a Philip Pearlstein painting :)
Mec4D, that shader work you're doing looks so good. Has me very excited to see Iray procedural texture packs hit the DAZ marketplace in the near future. I want a big collection! Hoping for some geometry influenced dirt shaders and shaders with falloff mixing effects, as those are two of the only things which I used to use in Octane but don't know how to do in Iray.
Those are incredibly nice. Amazing work.
I was thinking about this, along with your image... The Metal flake under a glossy layer would provide some sss in itself theoretically, but the result is a bit shiny and reflective for a natural look to me. It seems more stylized. However, getting a pure sss shader to not look dull can be challenging also. An interesting 'cheat' might be to mix the two. I'm not sure how much rendertime it would eat, but combining two different shaders like this would allow one to control the amount of gloss/reflection vs more muted sss. Hair really has quite a range depending on things like how clean it is, what hair products are used, how coarse it is (especially the cuticle layer,) etc...
On a related note, most surfaces with a sss component are not one color beneath the surface, or even a smooth gradation of color. Skin, hair, etc, all are made up of various colored pigment. In trying to get a good sss for these, it seems using a colored noise map (relatively fine scaled) with the colors representative of the pigment colors might give a better result then a smoothly gradient texture. Specifically, giving a bit more of the natural randomness at an almost subconscious level that our brain often expects. Adding a bump noise map to the underlying surface might also aid in this, although this last part is probably part of what the sss component is trying to achieve.
Ahh, that was what I was forgetting.. roughness. You are correct, a single value ior combined with a proper roughness value should give one the curve for a given material, or at least close enough.
Hmmm, aren't you talking about reflectivity? I thought roughness was equivalent to microsurface (that's how Marmoset defines these terms).
No, I meant roughness and exactly as Marmoset refers to it, microsurface. It's the microsurface roughness that causes dispersion patterns. More specifically, reflectivity defines how much is reflected*, roughness defines the dispersion pattern. The NVIDIA GPU Technology Conference video touches on this at 12" in.
* To clarify, in environments where reflectivity is a parameter, it usually is used to define an amount of overall reflectivity. In many environments, reflectivity is a derived value and one of the primary parameters which define what that derived value is, is roughness.
My latest render, entitled 'Jayce seated at the piano', which took my poor CPU reliant, 2 core computer 14.5 hours to render with 4869 iterations. :ohh:
Definitely will be needing a new computer for Iray, once I finally make up my mind what spec to get, a decision which is taking me months. :red:
:-)
This is probably a good thing as I expect there to be a significant jump in performance per dollar come fall.