Low light artifacts on face from the Human course.

[Jonatan Lyssens]

I was trying out different renders for my character from the Human course and I’m getting strange like a burned scorched skin like effect in the low light areas. In previous renders I never had that and it is only in low light. I attach both the low light Rembrandt type lighting and an overexposed version. Could some point me to what I’m doing wrong? Thank you in advance. 

Any other feedback on the character will also be appreciated. (full disclosure the hands were taken from a base mesh, but I textured them myself.)

[Martin Bergwerf]

Hi Jonatan @JonatanL 

That looks like Subsurface Scattering. SSS can look completely wrong in some lightings and totally fine in others (you should try to get it to look right in any lighting situation).

Try to reduce it, in modern Blender Versions, you should reduce the Scale, in older versions, you should just lower the SSS:

[Omar Domenech]

Also is it a cycles render or EEVEE? They each have their pros and cons. I think I remember a video from JL where he adjusted a setting to get rid of some shadow issue EEVEE was known to cause. The character itself looks good, there is a lot of work there, from the clothes and props alone that is some major work. 

[Jonatan Lyssens]

Thank you very much for your input and possible solutions. My apologies for my late response, but I was doing a lot of test renders and couldn’t figure out what I was doing wrong. I tried varying the scale settings of the subsurface, with no real effect. I saw the pattern change but it wasn’t going away really. So then I tried appending the model in a new blender project and it was gone. Then I remembered that I had reduced the max bounces for optimizing render speed in a high light set up, but that might have had a bad impact on the subsurface in a low light set up. So I will now have to re-evalute the light paths for this new set up. Thanks for the help. And Omar, yes this has been a project that has grown in the making. I started with the human course last year October and then I kept adding and adding… I have learned a lot. Looking forward to starting my second character in the near future.

[Martin Bergwerf]

Hi Jonatan,

That is a bit weird, as far as I know, Light Path Bounces have no effect on SSS….

But yeah, probably because it changes how much light actually hits the surface, that can become an issue.

(I think it took me about 9 months to finish Human.)

[Jonatan Lyssens]

Hi Martin,

You are right. It probably isn’t the number of bounces, but another thing that I did. So I tried to have an HDRI have an effect on only the armour. So that it wouldn’t look black, or at least not to black because there wasn’t anything reflecting it. Even with light linking, it felt to me to uniformly black. So I searched for a different solution, so in my world settings I toggled everything on for Ray Visibility except for the diffuse. So the shiny armour would be affected, but the rest of the scene only limitedly. I’m not sure why that would mess up the SSS. 

I will need to do some further render test to see if this is really the cause of it all. 

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