Sss makes geometry lose smoothing.

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Sss makes geometry lose smoothing.#384857

By Fernando Tella - Thu Jan 15, 2015 10:29 pm

- Thu Jan 15, 2015 10:29 pm #384857

Hi,

I think I've found a bug with sss (or thin sss). While using thin sss with emitters I've noticed that it made polygons stand out as if it ignored surface smoothing.

Here is a sphere with thin sss (in an additive layer) and an emitter inside (obviously, the sphere should look smooth):

Also happens with regular sss:

http://www.ftella.com

Re: Sss makes geometry lose smoothing.#384891

By Fernando Tella - Tue Jan 20, 2015 12:32 pm

- Tue Jan 20, 2015 12:32 pm #384891

Anyone else?

http://www.ftella.com

Re: Sss makes geometry lose smoothing.#384892

By T0M0 - Tue Jan 20, 2015 1:35 pm

- Tue Jan 20, 2015 1:35 pm #384892

Please could you share your SSS and ThinSSS settings ?

I saw similar result when I pushed values to extreme (Transmittance was few mm, Coef about 2 000,...).

Re: Sss makes geometry lose smoothing.#384910

By Fernando Tella - Tue Jan 20, 2015 8:08 pm

- Tue Jan 20, 2015 8:08 pm #384910

I can't, as I didn't save this test scene. What I've noticed is that the bug is more visible when the sss component is more dominant in the material. If a have some time I'll try to reproduce the problem.

http://www.ftella.com

Re: Sss makes geometry lose smoothing.#384914

By T0M0 - Tue Jan 20, 2015 9:47 pm

- Tue Jan 20, 2015 9:47 pm #384914

Something like this ? I think that values are wrong or too high. Or this is an example how to do it wrong

Would be really great to see, how to use ThinSSS correctly with few examples on Maxwell Blog

[SL=18]

Re: Sss makes geometry lose smoothing.#384928

By Fernando Tella - Wed Jan 21, 2015 3:16 pm

- Wed Jan 21, 2015 3:16 pm #384928

Here I come back with my homework done.

I picked a model from one of my scenes and illuminated it with an mxi emitter.

In this first image it has front and backface materials both with thin sss. You can already see faces without smoothing:

Then removed the backface material and made it its only material (so, no textures were used). You can still see some faces without smoothing specially at the back lit part. It is still a bit complex material with a bottom opaque layer with 2 BSDFs and a thin sss layer in additive mode on top of it. It also shows the "penumbra limit" shading problem, but that's another subject:

In order to simplify the material I then deactivated the bottom opaque layer leaving only the sss component. In this test you can see unsmoothed faces everywhere as it's color comes only from sss: