3 ms·

This is beautiful work! First, I thought this would involve using PCA to go from 3D to 2D, which would result in an easier selector to use, but at the expense o

This is beautiful work! First, I thought this would involve using PCA to go from 3D to 2D, which would result in an easier selector to use, but at the expense of representing every person. Then, I thought this would stop at using the U-space vectors (the ones that form the basis of the PCA image) and their corresponding ellipse to form our color space, but no, the function fitting is a very slick idea, even if it was executed by hand. Lastly, I love the presentation of sampling from different r values. Whether you sample from a fixed r value or a range of r values, I bet this has great applications in game design or animation. I still don't quite get the manual data labeling process at the beginning? It seems like it would encode some bias, but the consistency of the first point cloud and the results certainly speak for themselves.

automatoney 2mo ago
Thank you! I call out the manual labeling bias and also that a future work improvement would be to be scientific about that labeling process (multiple labelers, expert labelers), and then to feed that into the equation generation steps. Part of where the "good enough" naming comes from - I was hoping that using my art brain and keeping a bunch of reference images in mind (shout out to the Humanae project) would maybe offset the bias a bit. But 100% right on the bias being there.
dr_scully 2mo ago
If you look at my doctoral thesis, in fact skin colour can be parametrised using melanin and haemoglobin concentration; which it means it is indeed (roughly) two dimensional. This allows you to invert the colour of a pixel and identify someone’s chromophore concentration. This is based on previous work of others cited in the thesis. https://discovery.ucl.ac.uk/id/eprint/10093345/ https://discovery.ucl.ac.uk/id/eprint/10093345/
- GolDDranks 2mo ago
  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?
  - skydhash 2mo ago
    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.
  - Joel_Mckay 2mo ago
    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 https://kuhantilope.gumroad.com/l/ultimate-skin Best of luck =3
    - CITIZENDOT 2mo ago
      I didn't know chin/neck are slightly bluish, can we make it more explicit without side effects?
      - Joel_Mckay 2mo ago
        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/ https://www.udemy.com/course/blender-3d-sculpting-course/ Best of luck =3
    - iwontberude 2mo ago
      > 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.
- dTal 2mo ago
  Oh goody, an expert in a question I've always wanted to ask. Once upon a time, I encountered a sort of interactive museum book called "Earthsearch". One of its "exhibits" was a color wheel, made of two spinnable pieces of tinted acetate, that purported to be able to generate any skin tone. I suppose this is three degrees of freedom, since for any position of the two wheels you could access a range of colors around the edge - but the printed page underneath was simply a grayscale gradient, so one degree of freedom was simply luminance. The book was released in 1994, and was very confident. It even went as far as to encourage the reader to see a doctor, should their skin tone not be achievable! What color model were they using?
  - mhink 2mo ago
    Oh man, that's a blast from the past, I think I had that book! Was that the one with an aluminum cover?
    - dTal 2mo ago
      That's it! They (rather dubiously) claimed it came from a recycled Russian coke can, if I recall.
      - vector_spaces 2mo ago
        I had that one too. I remember I used to crunch on the rice from the bag it came with (I was like 8).
    - ReactiveJelly 2mo ago
      I loved that book! Was it that book or its sister that had an image of the pole and said "Spin the Earth the correct direction"? That and "How Things Work" kicked so much ass
  - dr_scully 2mo ago
    That’s sounds very interesting. I’m not sure. In the thesis, I generated spectral curves and transformed them using the light and camera sensitivity curves. So, in theory it could be used in any color space. But I can’t vouch for the accuracy of the book, but I suspect it was an approximation. The haemoglobin and melanin are roughly in separate layers of the skin. There is an approximation known as Beer-Lambert that models the skin as two semi-transparent layers. This ignores subsurface scattering, but is roughly correct. So, in theory two acetate sheets might replicate this. That’s my intuitive opinion. It has been many years since I did this work.
- mdnahas 2mo ago
  Not in dr_scully’s reply is that his thesis says haemoglobin is not static. Blood flow to the skin can vary over time.

automatoney 2mo ago

Thank you! I call out the manual labeling bias and also that a future work improvement would be to be scientific about that labeling process (multiple labelers, expert labelers), and then to feed that into the equation generation steps. Part of where the "good enough" naming comes from - I was hoping that using my art brain and keeping a bunch of reference images in mind (shout out to the Humanae project) would maybe offset the bias a bit. But 100% right on the bias being there.

dr_scully 2mo ago

If you look at my doctoral thesis, in fact skin colour can be parametrised using melanin and haemoglobin concentration; which it means it is indeed (roughly) two dimensional. This allows you to invert the colour of a pixel and identify someone’s chromophore concentration. This is based on previous work of others cited in the thesis. https://discovery.ucl.ac.uk/id/eprint/10093345/ https://discovery.ucl.ac.uk/id/eprint/10093345/

GolDDranks 2mo ago
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?
- skydhash 2mo ago
  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.
- Joel_Mckay 2mo ago
  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 https://kuhantilope.gumroad.com/l/ultimate-skin Best of luck =3
  - CITIZENDOT 2mo ago
    I didn't know chin/neck are slightly bluish, can we make it more explicit without side effects?
    - Joel_Mckay 2mo ago
      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/ https://www.udemy.com/course/blender-3d-sculpting-course/ Best of luck =3
  - iwontberude 2mo ago
    > 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.
dTal 2mo ago
Oh goody, an expert in a question I've always wanted to ask. Once upon a time, I encountered a sort of interactive museum book called "Earthsearch". One of its "exhibits" was a color wheel, made of two spinnable pieces of tinted acetate, that purported to be able to generate any skin tone. I suppose this is three degrees of freedom, since for any position of the two wheels you could access a range of colors around the edge - but the printed page underneath was simply a grayscale gradient, so one degree of freedom was simply luminance. The book was released in 1994, and was very confident. It even went as far as to encourage the reader to see a doctor, should their skin tone not be achievable! What color model were they using?
- mhink 2mo ago
  Oh man, that's a blast from the past, I think I had that book! Was that the one with an aluminum cover?
  - dTal 2mo ago
    That's it! They (rather dubiously) claimed it came from a recycled Russian coke can, if I recall.
    - vector_spaces 2mo ago
      I had that one too. I remember I used to crunch on the rice from the bag it came with (I was like 8).
  - ReactiveJelly 2mo ago
    I loved that book! Was it that book or its sister that had an image of the pole and said "Spin the Earth the correct direction"? That and "How Things Work" kicked so much ass
- dr_scully 2mo ago
  That’s sounds very interesting. I’m not sure. In the thesis, I generated spectral curves and transformed them using the light and camera sensitivity curves. So, in theory it could be used in any color space. But I can’t vouch for the accuracy of the book, but I suspect it was an approximation. The haemoglobin and melanin are roughly in separate layers of the skin. There is an approximation known as Beer-Lambert that models the skin as two semi-transparent layers. This ignores subsurface scattering, but is roughly correct. So, in theory two acetate sheets might replicate this. That’s my intuitive opinion. It has been many years since I did this work.
mdnahas 2mo ago
Not in dr_scully’s reply is that his thesis says haemoglobin is not static. Blood flow to the skin can vary over time.