I've heard that the so-called "yellowish" skin color that non-tanned East Asians tend to have, is due to relative abundance of subcutaneous fat. If that's true, is that captured by the haemoglobin dimension or is it a yet another degree of freedom?

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dr_scully 4 hours ago | parent | next [-]

We used the approximation that the hypodermis was a perfectly white reflector; so the thickness wouldn’t matter. The collagen fibrills scatter light in such a way to create a yellower tint. So a person’s skin might appear this way in the absence of melanin and haemoglobin. I’m not an expert on population statistics, and so cannot give an opinion on specific skin types. Everything was based on ranges.

There is a separate effect of increased bilirubin content, that would appear if someone was ill.

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HanClinto 3 hours ago | parent [-]

This brings up an interesting topic of atypical compounds that can visibly affect skin coloring -- whether temporary or more long-lived (such as elevated methemoglobin levels in the Blue Fugates of Kentucky).

It's fascinating to learn that melanin and haemoglobin are the two primary factors (and cover the vast majority of cases), but I'm curious how many other illnesses / disorders can produce compounds with visible effects.

Thank you for your posts on this thread -- I appreciate you knowledge-sharing on this!

	▲	dr_scully 3 hours ago \| parent [-]
		In theory, you can construct a skin model of any condition you want. It would be a case of knowing the concentration, scattering profiles and reflectance spectra of any chromophores. For the thesis, I wrote a Monte Carlo skin simulator using OpenCL, when it has just come out. You could plug anything in there.

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skydhash 4 hours ago | parent | prev | next [-]

Not an expert, but when I was learning 3d modeling, there was a good chapter on subsurface scattering which affect the human skin rendering. It’s what give it liveness instead of looking like a doll.

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Joel_Mckay 4 hours ago | parent | prev [-]

All skin is slightly translucent, and color/tones forms a gradient across the surface of the skin. Your upper cheeks and forehead are usually slightly reddish, and the chin/neck are slightly bluish.

People only turn yellow if they have kidney or liver damage. However, some distinctive features like Lucy Liu's natural freckles are tough to draw right.

We looked around a lot for a procedural texture/shader to help make the project characters look less sickly, and please also consider supporting the persons work if you are able:

https://kuhantilope.gumroad.com/l/ultimate-skin

Best of luck =3

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CITIZENDOT 2 hours ago | parent | next [-]

I didn't know chin/neck are slightly bluish, can we make it more explicit without side effects?

	▲	Joel_Mckay an hour ago \| parent [-]
		It is a classic artist starting off point to first drop a red/blue gradient as a base mixing layer, and add skin details/masks for each additional texture layer/feature. The "The Ultimate Blender 3D Sculpting Course" covers several sculpting techniques, and while this course has a number of challenges it does cover several basics. Probably wise to wait for a sale event if interested. https://www.udemy.com/course/blender-3d-sculpting-course/ Best of luck =3

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iwontberude 3 hours ago | parent | prev [-]

> People only turn yellow if they have kidney or liver damage.

This is not true. Roughly 5% of people have Gilbert's Syndrome which is genetic, metabolic abnormality where the bilirubin from dead blood cells are conjugated slower than the baseline patient leading to yellowing of the skin. It is not due to liver damage or disease and is a benign condition. Not to mention there is carotenemia from eating too many carrots or squash -- again not kidney/liver damage related.

	▲	Joel_Mckay 3 hours ago \| parent [-]
		Gilbert's Syndrome is a genetic disorder that causes liver malfunction, and people can't produce proper enzymes. This thread discusses physiology in an art context. Maybe get outside for a walk, and consider if LLMs are making people silly. =3