How to render sss pass separately

Support Compositing and Post Processing
1

Hi.
Since I have too noisy SSS in my scene, I need to denoise it separately from diffuse to avoid blurring it due to denoising. It was possible in old versions of blender but now these passes are always combined together. Is there a way to get the SSS pass separated?

2

I guess you have to duplicate for example the Prrincipld BSDF used in your material into one with and one without SSS and then use AOV Output to subtract the withoutSSS from the withSSS… to get the
pure SSS ??

1 Like
3

Yeah, and I don’t know how to get that pure SSS.
Here’s the example, custom AOV node expects the color data, but I don’t have any color data for SSS

image
image891Ă—1149 200 KB

4

Ouch… :person_facepalming:… silly me… yes of course…
…then i guess ( but it seems i’m very bad in this…) you have to render more samples… :frowning:

5

Yeah, it would help, but if I did it, I would render my animation like… forever

6

I figured out a workaround.

  1. Make the diffuse input of the Principled BSDF node black and enable SSS, then bake the diffuse pass into a texture
  2. Disable SSS in the Principled BSDF node and connect the diffuse input back
  3. Connect the baked texture to custom AOV node, then enable it in Render passes settings
  4. Done. You have SSS pass separated and it’s ready to be denoised and combined with the diffuse pass.
    Pros:
    It’s almost “free” SSS because it was already calculated.
    Cons:
    It’s static.
    I hope someone will find this workaround useful.
2 Likes
7

It would never came to my mind that a black color would give a result for SSS…

8

Since SSS pass always combined with Diffuse pass even if you bake it, it should be temporally disabled so you can bake the SSS only. That’s why you need to make it black

2 Likes
9

You could always make the SSS render in eevee separately. I will be noise free and faster. However not exact.