Subsurface Scattering Questions

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Old 04 April 2013   #1
Subsurface Scattering Questions

Hey guys, so after practicing modeling for a bit, I was looking on one of the skin tutorials to follow and it was talking about subsurface scattering and its role on skin (i obviously knew that was one of the main keys to put in for a realistic skin affect) and it got me wondering. How important is subsurface scattering? Is it used for all sorts of materials in general? Is it also one of the main keys to generate realism in all scenes? These questions are general questions-not specific questions. Hope to hear from you guys soon!


PS: I will definitely be working on learning subsurface scattering as I do know it is very important and very relevant
 
Old 04 April 2013   #2
it's super important for anything organic if you're going for any sort of realism
 
Old 04 April 2013   #3
It's used for a lot more than organic things.
Believable thin plastics, waxy surfaces, even some minerals, and a lot of other things require it in their shading to achieve a nice response to lighting.

It used to be something you only did for skin because skin without it was utterly terrible, so you soaked in the expense, but nowadays it gets used for a lot more.

These days, with the shading models and contributions providing so much complexity that used to have to be provided by hacky textures and lighting, it's not uncommon to have it participating to some extent in almost any hero item that doesn't actually directly suffer for it, if your engine and times can take it, that is.

Even hair we're applying SSS to these days when we can

Successful shading is, often times, 99% abut a complex and interesting response to lighting, and not a game of textures and magic numbers alone anymore. With such a shift in how we shade realistically, anything modelling a common behaviour of light is hardly ever left out.
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Old 04 April 2013   #4
marble & granite can also be somewhat translucent, i tried... the crystalline portions.. at least that's what my eyes tell me.

look at the Pieta by Michelangelo.. the cloth at the top of her head has a bit of subsurface quality to it.. remarkable.
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Old 04 April 2013   #5
Marble is a classic SSS example, alongside some precious or semiprecious cloudy stones (Jade another classic).

Basically SSS offers a well explored (and therefore optimized and served with tools) toolset to model light interacting indirectly with surfaces.
Energy radiation from the direct source out, backlighting and so on in a number of materials can be approximated with it and add a lot of richness to the surfacing's response to the environment.
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Old 04 April 2013   #6
SSS is important, but I often see overused SSS on poor textures, and it doesn't look believable. From the other side, Ive seen very believable characters without SSS, but with great textures and lighting.
So, SSS is great, but you should never forget the importance of the good textures.
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Old 04 April 2013   #7
If with believable you mean photorealistic, or at least shooting for that look, I have to say I can't honestly remember having -ever- seen realistic skin with no SSS. Good looking models with great textures, sure, but plausible skin without SSS, not really.

It goes without saying that you can't fix bad components with a rich technique (although a good ubershader and good lighting will make even some hella sketchy textures look gorgeous compared to the opposite), but I've seen excellent skin with very sketchy masking textures, hardly any complex colour textures, and just a solid displacement and dermal map on a very good shader.

Do you have any examples of plausible, good looking skin with no SSS you were thinking of and that you could link?
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Old 04 April 2013   #8
This I think is a fantastic example of doing realistic skin 'back in the day', when tech was helluva lot more limiting.



I'm by no means experienced in the matter, but I'll try to contribute to answering the OP - the main thing that generates realism in scenes is the lighting conditions (dome lights and physically accurate bounces). Most 'standard' raytracing shaders will give a realistic response, and from there on it's all about driving the look you want. If the look has prominent scattering (think jade, milk, and so on), cheating it would take more time in setup than you'd save in render time.
 
Old 04 April 2013   #9
Hey Jaco, I was referring on the movies from the 90's, and alsio on some of the work from here and 3D Total forum, I saw long time a go (If I find something, I'll post it up).
For example: Jurassic park movie.
I don't believe that they were using SSS shaders back in the '93, and all the dinosaurs looked incredible (at least, imho).

Also, I think SSS in some of the shots can be painted directly to textures... it's fake... but if it looks real, then it's Ok.

I'll search some exact samples.
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Old 04 April 2013   #10
Here's one sample of making realistic skin renders without using SSS (even without GI).
http://forums.cgsociety.org/showthr...utm_term=829134
You can download 3DS Max scene from the Hairfarm site.

I can't find the one more sample I have in mind, and if I do, I'll add it here.

Just to confirm: I am not saying SSS is bad, or anything (read my first post), just saying that I often see people trying to make SSS do all the work for them, not paying too much attention to textures. I think, once textures are great, it's not hard to setup a good SSS.
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Old 04 April 2013   #11
Originally Posted by d4rk3lf: Here's one sample of making realistic skin renders without using SSS (even without GI).
http://forums.cgsociety.org/showthr...utm_term=829134


You can get away with a lot in B&W.
More important than SSS in this situation is the specular response which is something a lot of people overlook, and is just as important in realistic skin as the SSS itself, but that's a whole other topic.

To answer the OP, you definitely should use it, but subtlety is key. Don't overdo it.
 
Old 04 April 2013   #12
Originally Posted by d4rk3lf: Here's one sample of making realistic skin renders without using SSS (even without GI).
http://forums.cgsociety.org/showthr...utm_term=829134
You can download 3DS Max scene from the Hairfarm site.

Thanks for the link. I remember that picture, but I wouldn't count a B&W still with abundance of photoshop for much in those regards.
In stills you can cheat the hell out of things with diffusion and rim maps and clever lighting.
As soon as something moves though, camera, lights, character, let alone any two, it falls apart.

Quote: Just to confirm: I am not saying SSS is bad, or anything (read my first post), just saying that I often see people trying to make SSS do all the work for them, not paying too much attention to textures. I think, once textures are great, it's not hard to setup a good SSS.

I understand what you're saying, but I'll respectfully disagree.
You hardly ever need GREAT textures if you have a great shader, while even the best textures will fall flat (literally, in terms of lighting) without a decent shader.

Of course both done to a great level is your best option, but in production I've rarely, if ever, seen the case where the shader was an easy job and all the work was left to textures, it usually results in very subpar results once things move, often barely works for the turn tables. The ubershaders for heroes usually take the largest chunk of look-dev time and are built on tall stashes of previous experience, and the textures are iterated relatively quickly as needed.

It's definitely NOT easy to get a good SSS setup, unless you're just playing a game of magic numbers to get the one still in the one pose from the one angle out quickly, in which case you're more painting with light for the one frame than you are doing shading work.

If you have the shittiest of textures, of course things won't look good, but that's a truism at best. If anything is truly crap in the chain things won't look good, textures being only one of many things.
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Last edited by ThE_JacO : 04 April 2013 at 11:37 PM.
 
Old 04 April 2013   #13
fantastic info guys! Thank you all for informing! So in practice--use it, but don't over-do it. Got it! Any other important details I shouldn't miss or stuff you guys would like to add? I am pretty satisfied with all that you guys said, but any extra i will definitely welcome.
 
Old 04 April 2013   #14
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