Huge issue: SSS + fake shadows messes up phong angle

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Huge issue: SSS + fake shadows messes up phong angle

Postby Jengo_1 » Sat Dec 19, 2020 7:18 am

Jengo_1 Sat Dec 19, 2020 7:18 am
Hi, so this is a huge issue that simply doesnt have an answer, and I've spent months looking for an answer. I always ended up compromising but I have a project that requires extreme realism and I want to figure out what is going on.

So, as was already discussed here, SSS with fake shadows on removes phong angle from model. That results in a heavily faceted look.
Here are the "solutions" that don't really work on the internet:
1. Increase Subdivision Surface - Doesn't resolve faceting, just makes polys look smaller and still faceted. Also, makes scene unreasonably heavy.
2. Increase Ray-Epsilon - This works, but it causes other huge problems. One is that the color of the SSS becomes extremely saturated and dark, and there's no real way to fix it as much as I try to make the color and scatter lighter. Also, It causes ugly artifacts in the small details where objects overlap or are placed close to each other due to the higher ray-epsilon.
3. "Smooth" option on the Common tab in the material doesnt fix it. Messing with the phong tag doesn't fix it.
The only thing that actually works, is unticking Fake Shadows. But then, the SSS requires high scatter depth.

Here's the examples
First I tried to work with the exported DAZ model I have, this has Ray Epsilon of 0.00001 (Needed a lower Ray Epsilon to solve something else in this scene):
SSS_ShadowCatcher_RayEpsilonLow.jpg


After trying endless of different combinations and fixes, I tried to work with a model known to have perfect topology and textures to see if I still get it

Ray Epsilon 0.0001:
SSS_ShadowCatcher_RayEpsilon0.0001.jpg


Ray Epsilon 0.001 (look at the artifacts where the lips and eyelids touch):
SSS_ShadowCatcher_RayEpsilon0.001.jpg


And here's how it looks with no Fake Shadows on ray epsilon 0.0001:
SSS_ShadowCatcher_NOSHADOWCATCHER_RayEpsilon0.0001.jpg


As you can see, the fake shadows cause this issue. Is this a known and unfixable Octane in C4D issue? Because I've seen people get good results without faceting using this technique in Octane on other programs or not using Octane.

Here's how I made the material - Albedo is black and Transmission is on 100.
SSS_Material.jpg


Any tips of other tricks? Is this simply not the way to achieve highly realistic skin in Octane for C4D?
Should I just use a different approach to SSS that might look less realistic?

Thanks!
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby bepeg4d » Mon Dec 21, 2020 9:42 am

bepeg4d Mon Dec 21, 2020 9:42 am
Hi,
if you need to adjust the ray epsilon value, it means that the scale of the mesh is not correct, for the scale of the scene.
Please, check the mesh scale, and assign real world dimensions, or everything will not work as expected.

ciao Beppe
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby Jengo_1 » Tue Dec 22, 2020 6:48 am

Jengo_1 Tue Dec 22, 2020 6:48 am
Hey Bepe thanks for replying!
Yeah I guess in my long message I forgot to also cover the fact that it's all real world scale, both heads are around 11cm Radius.
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby Jengo_1 » Sat Jan 02, 2021 10:32 am

Jengo_1 Sat Jan 02, 2021 10:32 am
Hey so Bepe or anyone, so once we realize everything is in real life scale and that all the options were depleted - are we declaring this as an official bug? Is this something that's going to be fixed? It's a really frustrating issue, and weird that there's no responses about this issue anywhere. Thanks!
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby bepeg4d » Mon Jan 04, 2021 8:12 am

bepeg4d Mon Jan 04, 2021 8:12 am
Do you mind to share your scene with me via Private Message?

ciao Beppe
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby kabakZ » Sat Jan 09, 2021 10:38 pm

kabakZ Sat Jan 09, 2021 10:38 pm
Hi, I am not a C4D user but I faced this problem too.

The easiest way to get rid of visible normals is switching to Diffuse mode for Universal Material insted of Specular. For some weird reason, Random Walk SSS and Specular mat fails on Daz3D models (quad topology), BUT at the same time it works for other models with triangle or triangulated topology or non-Daz quad topology.

I have no idea how OTOY test their stuff. The initial implementation of Random Walk has visible UDIM seams on Daz models, now it has visible normals with spec mats on Daz models.
Hope we get a more stable Random Walk SSS in future releases :roll:
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby andrevieira » Fri Apr 08, 2022 11:53 am

andrevieira Fri Apr 08, 2022 11:53 am
Hi,
Having the same issue on Octane for Blender.
Tried on releases 2021.1.3 and 2021.1.4, same results.

Check the attached images.

Cheers, André
Attachments
ShadingIssue_Shader.jpg
ShadingIssue_Mesh.jpg
ShadingIssue_Render.jpg
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby bepeg4d » Mon Apr 11, 2022 6:41 am

bepeg4d Mon Apr 11, 2022 6:41 am
Hi,
try to use also the Transmission channel/pin too, and try to change the Transmission type from Specular to Diffuse.

ciao,
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby Banti » Thu Apr 14, 2022 7:42 am

Banti Thu Apr 14, 2022 7:42 am
Switching to a diffuse material or diffuse transmission (when using universal material) does NOT fix this issue. Here is what random walk looks like on a diffuse material (using DAZ plugin):
diffuse.png


And here on a specular material:
specular.png
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Re: Huge issue: SSS + fake shadows messes up phong angle

Postby bepeg4d » Fri Apr 15, 2022 7:43 am

bepeg4d Fri Apr 15, 2022 7:43 am
Can you share a screenshot of Random Walk node?
Universal material is tricky, since it depends on which channels/pins you are using.
If Albedo is not Black, you should set the Transmission to Diffuse.

ciao,
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