How to go about the new SSS option?

[N-drju]

And no - not the simple shape shader.

I have just created a simple candle in blender and I would like to apply a sub surface scattering (SSS) to said model. What should I apply or add to the object's material to get started and tweak away?

Obviously, nothing has changed in the "default shader" alone, so where should I look first instead?

[Dune]

You should add a glass shader first, instead of the default. Set a small value for decay distance (1cm or so), and a nice candle color for decay color. Volume density to 1-2 or so and color to 1 or 2, depending on what comes out. Then tweak from there. You can add a color pf to color input too, for some variation. It's basically the color input of the glass shader that gets its SSS depth by that glass shader, so even an image map would work, if it's properly UV'd. This is what I know/think. Maybe someone has a fullgrown tgc for you

[N-drju]

Oh, no, no way. This is too nice an effect to have it done by someone else. I'll just try these steps and see if I can get what I want.

I wonder though if I can add other shaders above the SSS-generating glass without killing the effect...

[WAS]

I wonder though if I can add other shaders above the SSS-generating glass without killing the effect...

Maybe if you first apply it to a surface layer and use like 0.5 coverage so it has some opacity for the SSS to work. Not sure.

[N-drju]

Well, I tried to put the advice into practice, but it leaves a looot of work to be done.

I also noticed that the object itself needs to be improved. Maybe this is why the effect looks so bland and is more of a luminosity than SSS...

[Oshyan]

First question would be: is your candle model to real-world scale?  If not, either adjust it so it is, or increase the values Dune suggested.

- Oshyan

[N-drju]

The candle is not up to scale, but I was aware of that and adjusted the decay settings accordingly. I leave the colour settings out though - I reckon they should not be size-dependent...?

[N-drju]

Right... So I made some more tests.

I'm not satisfied at all... I can see a promise in these images if I employ my imagination... But the fact remains that SSS effect is very tough to achieve.

I have come to the conclusion that the "transparency" setting is just as important as the "decay distance" is. I have no idea though, why the candle surface is so grainy and unnatural - even with an extensive use of path tracer and "max paths per sample" setting (increased to "architecture" in the examples below.)

From left to right - candle rendered with PT (0.5 / AA3) with decreasing transparency (1 - 0.17 - 0.07) setting, "decay distance" set to 0.4 and a yellowish volume colour set to 1.

     

[N-drju]

I have no idea what exactly am I doing wrong, but I just can't get "SSS" to work... I made several more (lousy) tests and it seems that subsurface scattering will work only in some situations and only with some objects.

I tried to put it to work with the native sphere object and here is the terrible piece of junk that I got...



Seems like a waste of electricity and time...

[WAS]

That's a really strong colour to really see the effects very well, and causing colour burning in the final render. I'd lower the brightness of the light by a lot.

SSS does have issues with geometry it seems. Some areas it just decides to disable base on the geometry.

[N-drju]

SSS does have issues with geometry it seems.

Certainly looks like it. I must admit that I kept wondering if an object's quality or a build style can play a role in how SSS is handled. The impression I get today after almost an entire day of testing is that these elements do influence the final result. It probably has to be a darn well-made object to handle the light interactions flawlessly... Not implying that my objects are poor - on the contrary, if I may say so myself.

With my yesterday's last breath, I have made some comparison renders with a native sphere but I used Hannes workaround SSS for that purpose. The result was so much better than the one generated by glass... If I were Planetside, I'd make another note next to the SSS option that reads "Not for production"...

Speaking of Hannes, I'd might as well check if there is anything "waxy" in his collection of materials. Some of these prooved really helpful before Chirstmas.

I just don't understand how could you possibly recreate an effect like the one with the Buddha (I guess...?) statue on the main page. Anything I try with the glass shader that has to do with SSS is just rubbish. In my view, it's Planetside waving a flag, saying "See? It's possible!" without offering even a piece of advice on how it works. This is even worse than the function problems because I can describe it only as a waste of electricity and time.

[Matt]

For scenes that are producing a lot of noise like this, try setting the "Max paths" to the highest setting available. Don't do this by default, but with noisy SSS renders it should help.

The anti-aliasing will need to be a lot higher than 3, even with the max paths setting increased to its highest.

Displaceable objects can be quite slow to render with path tracing, and when SSS interacts with them it's even slower. If possible, use imported objects or non-displaceable built-in objects.

Slow (displaceable objects): Cube, Disc, Octahedron, Plane, Planet, Sphere.
Fast (non-displaceable objects): Card, Grass Clump, Rock, LWO Reader, OBJ Reader, TGO Reader.

[N-drju]

Hi Matt. Thank you for your interest in this topic.

I'm sorry to say this, but your post does not help at all. As you can see above, the very first object I wanted to try out was, in fact, an imported object in the .obj format. Counting down what object types can and should not be SSSed is of no use. Describing how to use the glass shader to reproduce SSS is. Unfortunately you never made that effort and, as I already said, the only information we get is that "You can use SSS in the Glass Shader to render a whole range of materials with subsurface scattering effects". And...? How?

If I may suggest - please do a short guide on how SSS effect should be achieved. Just like you did with the Path Tracer!

This is another try of the SSS in a candle that I have made. As you can see, this has been rendered with really high settings. The effect however, is as abominable as it has ever been for me...

[Matt]

I'm surprised it's still so noisy. Can we test your TGD and object to understand why this is happening?

[WAS]

For scenes that are producing a lot of noise like this, try setting the "Max paths" to the highest setting available. Don't do this by default, but with noisy SSS renders it should help.

The anti-aliasing will need to be a lot higher than 3, even with the max paths setting increased to its highest.

Displaceable objects can be quite slow to render with path tracing, and when SSS interacts with them it's even slower. If possible, use imported objects or non-displaceable built-in objects.

Slow (displaceable objects): Cube, Disc, Octahedron, Plane, Planet, Sphere.
Fast (non-displaceable objects): Card, Grass Clump, Rock, LWO Reader, OBJ Reader, TGO Reader.

We need waaaaaaaaaaay higher paths Matt. Full paths and AA 9-10 for a noise filled render is silly. And AA is far more a impact it seems than ramping up paths.

I just posted this too. Nothing to do with TGDs. Just how soft light works in darkness under currents paths.

The "Extreme Lighting" paths setup seems more like "normal daylight", paths rather than extreme lighting, as in a extreme lighting instance, relying on lighting alone, it's a pixel show. I noted in my other post that documentation regarding Path Tracing, in most cases they were using hundreds of paths if not well over 1000. I'm not sure how this relates to TG though.