Why does SSS darken colors?

[itsallgoode9]

I'm working with the SSS materials trying to create a glossy plastic cap but it really doesn't work anything like expected. I'm working with a specular material and you can see below the difference in colors. This image is even after I've adjusted other settings to a point that aren't technically correct, but they help at least get to a point that I could tweak in photoshop.

Can anybody give me some guidance on this? Am I just doing this wrong from the beginning or is SSS still buggy since it's new?

[MaTtY631990]

Hi itsallgoode9

First try lowering the reflection on the specular material if you have not done so. Alternative option to try is using a mix material with diffuse for SSS and glossy material for reflection. You should be able to get better result. For diffuse material set color to black and use transmission color instead. Then add your scattering medium to this as well. For glossy material try index to 1 for full reflection.

[itsallgoode9]

Thanks, for the advice. I've start working with the mix material for this, as you suggested. The cap is a little semi transparent, so I don't think diffuse will work, but I've gotten some better results in working with the mix material using a couple specular materials.

I'm a bit worried how this affects render times and noise. If i'm using spec just to create glossiness in a mix material, is octane calculating IOR for caustics and such? For my needs, this is definitely overkill.

[MaTtY631990]

Really playing with this yourself is better, trial and error really but specular material is slower since you have reflection, refraction and light transmission through material than glossy material in terms of performance, so I would just stick with a plain glossy for IOR reflection. You would get reflective caustics of course so to avoid them set caustic blur to 1.

[dsyee]

Have you tried turning on "Fake shadows"? It seems to make a difference (and you probably don't want "real" shadows with scattering, anyway).

Also, the ray epsilon setting can have an effect on scattering.

[itsallgoode9]

i tried that but wasn't getting good results. what happens to your model when you turn up the scattering some?

[dsyee]

Didn't save that scene, but here's a similar one.

Another idea, though - how high is your diffuse depth?

[Edit: Images were supposed to be in reverse order, sorry for any confusion]