Absorption and In-Scattering.....Non-working shader channels? 8.5 pro

protovu · February 2015

Within the Transparency channel of the multi-channel shaders, has anyone a clue on how to activate the Absorption and In-Scattering sub-channels ?

I have examined all of the presets to see if there is any shader which uses either of these, and can find nothing.

Also, I have dropped every function available into these channels, and nothing happens.

Annoyance aside, seems like these could be very useful, yes?

Is there something wrong with my build?

thanks

evilproducer · February 2015

It does wrk. You also need to enable the checkbox for it in the top level of the transparency channel. It's near the bottom.

JoeMamma2000 · March 2015

Perhaps it might be a case of absorption and in-scattering working okay, but they just aren't doing what you expect? Since they are fairly esoteric concepts, are you familiar with what they should be doing? The reason I ask is because you mentioned that you put a lot of functions in those channels, but nothing happened. Typically, you need to put specific stuff in there for them to work okay.

protovu · March 2015

I believe that I do understand what to expect, but correct me if I am off base.
Actually, I am trying to find a way around SSS, which renders too slowly.
I have been experimenting with trying to emulate
a blender output that shows SSS. There is a file for download from a tutorial which you may have seen. The yellowish chess piece on the right is what I am after in Carrara.

evilproducer · March 2015

Did enabling the option in the top level of the transparency channel do anything?

Looks like in your sample that that there's a lot more going on than in-scattering and absorption. Looks like translucency and Fresnel effects for sure. There would also probably need to be a very fine bump on the surface as well.

protovu · March 2015

Yes, it did enable the In-scattering and Absorption sub-channels. I thought I posted a previous "thank you" on that, but I see that the post failed...Sorry about that. Hate to appear unappreciative! I was going nuts trying to find access....(right in front of my nose).

And, yes. You are absolutely right. In trying to achieve the look of sand-blasted glass, I am fiddling with bumps, Fresnel, translucency, Fake Fresnel....... Not seeing anything satisfactory yet. Will post if I do.

evilproducer · March 2015

Looks like maybe an HDRI for lighting and Indirect Light, so you'll want Skylight and Indirect Light enabled in the Render room. One other thought is that the Blender render may be an un-biased render, which could make the results look different as well.

protovu · March 2015

I will try the HDRI, but I am trying to avoid Indirect Light and Skylight in the render room.
Cycles is an unbiased renderer. This may mean that Native Carrara cpu rendering is not going to cut it. At least, not without
using SSS.

evilproducer · March 2015

An HDRI won't have any effect if you don't enable Skylight. That's what tells the renderer to use it.

I did have a non-GI thought that you could try: You mentioned you had tried Fake Fresnel? Have you tried that in the glow channel with a low intensity glow, set to the color of the object?

protovu · March 2015

I actually have use the Shader Ops FF in the glow channel, but inverted on another project. Tried it here, but maybe too strong, as you suggest. Will diddle some more.

evilproducer · March 2015

Maybe put a Mixer in the Glow channel and your color and Fake Fresnel tree in one slot and a black color in the other, then use a numeric slider for the mixer, and adjust as needed to dial up or dial down the intensity.

JoeMamma2000 · March 2015

I guess I'm a bit confused about what you're trying to accomplish.

The leftmost chess piece in the image you posted just looks uniformly grey, so I can't tell what effect you're trying to reproduce.

And typically, SSS or similar is used only with specific materials which exhibit the subsurface effects. Typical examples are milk, or jade, or candle wax, or human skin, or the like. If you're looking for a frosted glass effect, then typically that isn't a SSS effect, it's a fairly shallow surface bump, like Evil says, with the underlying material just normal glass.

So I'm not sure what you're trying to accomplish.

Normally what I will do is search for a real life photograph of the material I want, and try to reproduce that. And as Evil says, a lot of it has to do with how you light the subject. Jade and milk and skin don't look like jade and milk and skin unless you light them to look like jade and milk and skin... :) :) :)

But if you've found what you're looking for, then great.

I'd also add that, IMO, the SSS effect in Carrara isn't the best, and takes a lot of tweaking. And the same can be said for many of the other surface material effects. Not that they're all bad, just that it takes some work to get what you want. And sometimes (especially with glass), it takes a LOT of work, and the results aren't near what you can get with other software right out of the box.

protovu · March 2015

Did I indicate leftmost? My error, if so.
Seems earlier I indicate the yellowish chess piece on the right is what I am after in Carrara. And because SSS is slow, I would like to find a reasonable facsimile thereof, if possible. Honestly, I am after sub-20 second frames for animation at 1280 x 720, so I am trying to avoid some of the features which might give us nice still images.

Maybe this is not meant to be? Hate to give up on it. I realize that the wax shader is not a bad basis, but the SSS requirement makes it too slow.

What software are you partial to for this sort of thing?

JoeMamma2000 · March 2015

Oooppsss...sorry.

I guess when you said "right most" you meant on the RIGHT, not LEFT... :) :) :)

Anyway, looks to me like a frosted glass effect, with some fresnel like Evil said.

protovu · March 2015

no worried.
yes, that is what it is, indeed. Nice isn't it? Too bad cycles is so slow, and getting up to speed on Blender would pop a spring in my head.

JoeMamma2000 · March 2015

I recall that Carrara's fresnel effects are pretty horrendous, and most people use a plugin (I forget which).

But yeah, seems to me that the one on the right is intended to be a frosted glass, and it has some significant fresnel shading and some decent lighting to bring out the depth.

Personally, I'd do some online searches for some real images, not somebody's renders, and try to figure out why the subject looks that way and try to duplicate it. I think many people mis-apply various effects because they don't try to figure what the real world surface and material properties are, and as a result they get stuff that doesn't quite work.