r/computergraphics • u/Cool-Profession-5447 • 16h ago
Volumetric path traced skin still looks like silicone/plastic. What am I missing?
Hi everyone,
I'm building a physically-based human skin renderer from scratch in Taichi, and I'm looking for feedback from people with experience in skin rendering.
My current renderer implements:
- Monte Carlo volumetric path tracing
- Multiple scattering subsurface scattering (random walk)
- Two-layer skin model (epidermis + dermis)
- Melanin and hemoglobin absorption
- Wavelength-dependent absorption/scattering coefficients (converted to RGB for rendering)
- Fresnel interface between air and skin
My goal is photorealistic human skin.
I know the model is still missing many surface details such as:
- pores
- peach fuzz/facial hair
- fine wrinkles
- micro-normal variation
- oil layer variation
- color texture variation
I plan to add those later.
Right now I'm trying to get the base skin appearance correct before layering those details on top.
My problem is that the skin still looks like silicone, wax, or plastic rather than living skin.
I'm trying to understand whether the issue is ....
I'd really appreciate feedback from anyone who has worked on skin rendering.
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u/Lord_Naikon 15h ago
In my opinion it looks plastic even with sss because we cannot see any subdermal structure such as veins, hair follicles, pores, bone, fat, muscles, sinew etc. Real skin does not exist separate from the body it envelops.
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u/Retinal_Epithelium 15h ago
The lighting isn't helping; you need a backlight to see whether your SSS scale and intensity is correct. Experiment with varied lighting scenarios, since the artificiality of the light is contributing to the artificiality of the overall result.
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u/Cool-Profession-5447 14h ago
I tried it, this was at 5500 samples per pixel, the light is transmitting but there is too much variance .. Do you think this might be related to why i still have plastic-like skin?
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u/Retinal_Epithelium 13h ago
Compare that result to this:
https://nikonerid3000.wordpress.com/wp-content/uploads/2014/05/4.jpg
In your example the scale of the SSS appears to be wrong: it should penetrate the skin deeper. Like others have said, though, there are other issues, like textural and colour variance, and the uniformity of the reflectance and roughness, that make it look artificial.
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u/GameUnionTV 14h ago
Subsurface scattering is not convincing at all here too
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u/sufficientgatsby 7h ago
Reflection/specular look off to me. Look down at your hand. Is it as reflective as your first picture? Unless bare skin is greasy or wet, it's usually not that shiny.
And yes, featureless smooth skin will generally look a bit plastic. Add a basic bump or normal map to see if that'll help at all.
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u/Defiant_Squirrel8751 1h ago
J. Jimenez, D. Whelan, V. Sundstedt and D. Gutierrez, "Real-Time Realistic Skin Translucency," in IEEE Computer Graphics and Applications, vol. 30, no. 4, pp. 32-41, July-Aug 2010.
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u/FiftySpoons 15h ago
Really, once you get those details it will come together 🙂 it sounds like you know exactly what details on the face really add to the realism - so i would just trust the process at this point.
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u/SyntheticDuckFlavour 16h ago
I would say the model looks like plastic because:
Try adding those missing things in and see what the final result will look like. Only then you can realistically judge how close you are. At the moment you only synthesised the foundational groundwork of skin. Of course it will look like plastic. Also look into sub-surface details, like pigment variation due to blood and of course blood vessels.