How could I fix glowing teeth with the Subsurface Profile Shading Model?

mimicproductions
Fri, 04 May 2018 09:12:42 +0000
Rendering

I’m trying to make a realistic face using the Subsurface Profile for the skin-shader, like it is suggested in Epic’s photorealistic asset and in the released paragon characters. The character has facial animation, so if she makes a funneler with her mouth you can see the teeth, which are using the same shading model (but different textures and values obviously). Now these teeth seem to be glowing in the area that’s close to the lips outline. See the attached image.

The first thing I noticed is that my scenes lighting has a lot of contrast, which is probably making the effect even more visible, since it seems less visible in an outdoor skylight setting.

Second, I did some research on the Subsurface Profile shading model (Subsurface Profile Shading Model | Unreal Engine Documentation) which made me understand, that this shader apparently uses Screenspace information to “fake” a quite efficient subsurface scattering effect. So I guess the only information it has available, to render the effect on the teeth, is what we can see on the screen. And because the lips are quite bright, they bleed into the teeth. I also noticed, that the transition to the upper lip looks fine, probably because there’s shadow on that side of the lip and darker colors bleed less.

The other attached image shows a very basic setup of subsurface profile materials. If I reduce the Scatter radius, you see that the glowing effect mainly comes from the teeths subsurface properties.

So I think I kind of know the source of the problem (correct me if I’m wrong), but I don’t know how to resolve it. I would appreciate, if anybody has suggestions or ideas on how to solve the issue or bypass it.

Thank you

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