I’ve been looking around on the internet trying to find if Sub Surface Scattering was possible in Cycles. I didn’t need necessarily but it was an interesting topic so I decided to take on the idea myself. See how far I could get (Not that far mind you…). The end result I’ve attached here. (Part of me wants to make an SSS shader setup in order to assign it to unusual objects such as non-organic models.)
Anyway here is my final result:
It’s a good start, but SSS tends to be a very complex effect and may require a significantly larger and more complex node setup if you want to really push the use of the ray length output and Cycles shading in general.
The following is the result of a glossy translucent group node setup that got its start before the introduction of the new output and then was followed by weeks of off and on work and experimentation in an attempt to make a scattering effect that would probably not be physically correct (as we would need a real SSS shading algorithm for that), but convincing enough to be useful.
As a consequence, this ended up being the most complex node setup I ever made and one of the toughest shading challenges I ever undertook, the final changes to get to this point was just today, and over the last month or so, it took a lot of trial and error, experimentation, and an ever-so-often burst of thinking giving me a new idea to try to get there.
EDIT: Replaced the image with one showing a more dramatic effect with more samples, all changes were of values I set to reveal in the group node UI, not to its internal structure.
^^^ pretty neat, but makes me want a real SSS shader, I don’t think I’m up to the task of faking it! O_O
Well your effect is ten times better but the complexity of that node setup nearly gave me a heart attack. Being the crazy man I am I believe that it is possible to achieve it in a simpler way so I took another look at my setup and with a small degree of epxerimentation I have come up with this:
It’s still not perfect. Compared to yours not good at all (I admire the achievement in your setup) but I think it is one step forward. 
Cool node setup Ace Dragon - would you be able to post a higher res zoomed version of it so we can take a crack at replicating it.
Cheers
Luckily, we have node groups, below is the .blend file that contains the setup seen in the screen.
CyclesScatter.blend (492 KB)
Being the crazy man I am I believe that it is possible to achieve it in a simpler way so I took another look at my setup and with a small degree of epxerimentation I have come up with this:
It is better, but from what I see is not quite there yet, I recall from images made in other render engines that a light behind Suzanne should be giving a more or less translucent effect covering the entire inner region of the ear with a weaker effect around the edges and rather than just being in a small ring, you would also have the same effect around the very edges of the mesh that would be the result of rays scattering through a very short distance within the mesh before exiting.
I think with every post you reply with I improve my shader just a bit more. I’ve still stuck to my ideal of simplicity though and this is what I got:
Thank you Ace Dragon because if it weren’t for your comments I wouldn’t learn Blender better and get this result.
would you by any chance mind uploading a .blend with your node tree?
I was wondering…with Pathtracing algorithm, is it still possible to do Physically Correct SSS?
Absolutely, and it already done in volumetric patch.
Here is quick example.
Unfortunately it’s likely that the SSS feature has been put back on Brecht’s todo list, the student has not updated his status for up to a few weeks now so it’s likely that he dropped out.
You might want to approach Agus3D on this though, if there’s anyone other than Brecht who has the coding skill needed for such a feature, it’s him. Otherwise, it may be a while before we finally see true SSS shading.
