Hacker News: dr_scully

New comment by dr_scully in "GPT-6 Astra"

dr_scully — Thu, 03 Sep 2026 20:32:24 +0000

He also made a video on the same topic for Big Think: https://news.ycombinator.com/item?id=49551848

Terence Tao: Speed in science isn't the same thing as progress [video]

dr_scully — Thu, 03 Sep 2026 15:41:04 +0000

Article URL: https://www.youtube.com/watch?v=svl_1upFpQo

Comments URL: https://news.ycombinator.com/item?id=49551848

Points: 4

# Comments: 0

New comment by dr_scully in "Show HN: Simple algorithm and color space to generate diverse skin tones"

dr_scully — Tue, 04 Aug 2026 18:15:46 +0000

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.

New comment by dr_scully in "Show HN: Simple algorithm and color space to generate diverse skin tones"

dr_scully — Tue, 04 Aug 2026 17:25:15 +0000

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.

New comment by dr_scully in "Show HN: Simple algorithm and color space to generate diverse skin tones"

dr_scully — Tue, 04 Aug 2026 17:12:26 +0000

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.

New comment by dr_scully in "Show HN: Simple algorithm and color space to generate diverse skin tones"

dr_scully — Tue, 04 Aug 2026 16:20:37 +0000

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/

New comment by dr_scully in "GPT Unicorn: A Daily Exploration of GPT-4's Image Generation Capabilities"

dr_scully — Fri, 14 Apr 2023 10:26:06 +0000

If you ask it to write GLSL code implementing Signed Distance Fields, it can generate a 3D rendering of a unicorn as well. Just paste it into ShaderToy. I asked it to implement animation as well, for the legs, and it manage to do something although incorrect.