clipka <ano### [at] anonymousorg> wrote:
> Am 30.04.2016 um 16:59 schrieb Simon J. Cambridge:
> > I have been trying for ages to get satisfactory results with subsurface (both
> > POV 3.7 and Samuel Benge's fastSSS). I imagine I am doing it wrong in some way
> > as I can never get the results that I want! So I got to debating with myself as
> > to the whichness of the why and tried using Irid instead. After various tests I
> > came up with the following, ramping Irid up (2), using low lighting (fade
> > distance) and a small thickness (0.05). The results are as you see (but be
> > advised these are all very much works in progress!)
> >
> > One thing of note. It is very much faster than SubSurface. Also, I was wondering
> > whether there was any mileage in being able to use a colour component for the
> > strength, eg Irid <1, 0.7, 0.5>.
>
> Subsurface Light Transport and Iridescence are two entirely unrelated
> phenomena in nature, and entirely unrelated mechanisms in POV-Ray.
>
> If you find that the `irid` mechanism "kind of" does what you want,
> you're likely in for much frustration if you try to coax it into doing
> _exactly_ what you want, because it is probably designed to do something
> entirely different.
>
> Of course, figuring out what is _really right for you requires to get a
> clear grasp of what you actually want to achieve.
>
>
> SSLT is designed to make skin (and other materials, like wax, soap, or
> even milk) look less "hard" than the results you can get from classic
> rendering, to the point that it may look a little bit translucent.
>
> I'd like to point out that your attempts at employing `irid` for more
> realistic skin utterly fail in this respect (and inevitably so, for some
> very fundamental reason); your people still look like made from some
> hard plastic or plaster or something, and always will no matter how hard
> you try with `irid`. There are other fast cheats that might do the trick
> depending on the lighting conditions, but iridescence simulation is
> certainly none of them.
>
>
> If, on the other hand, what you're really after is just making the skin
> look a little bit more "oily", then you're on the right track after all.
> That's an effect that SSLT is unfit to simulate (so in that case it's no
> surpsise you're getting nowhere with that mechanism), while `irid` is
> indeed perfectly tailored for it.
>
>
> As for allowing to modulate the `irid` effect on a per-colour basis,
> that would be physically nonsensical, as iridescence _generates_ colour
> effects, and it does so based on some very fundamental laws of nature.

Thanks clipka.

I have tried with SSLT, I really have, but it never seems to give me what I am
after, which was why I went physically nonsensical. Skin ends up looking like
wax, or artifacts get generated (on meshes - light patches on vertexes).
Certainly, having played with irid, I do think there is mileage in the oily
effect, but only if you use it sparingly.

I have also tried scattering media and having objects inside objects, but that
makes modelling a nightmare. I would much prefer to get SSLT right as that is
clearly the most physically accurate, but I cannot seem to get what I am after
(artistically).

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