rainbow algorithm comparison

[yomikoma]

https://suberic.net/~dmm/graphics/postscript/documentation/all_rainbows.html

I added/fixed some rainbow algorithms in my postscript library and generated this image to compare them.

Comments

[cnoocy]

Interesting that the non-hsb ones are much less bright. Is that expected?

[yomikoma]

Yes! The hsb rainbow follows the edges of the rgb cube, which is as bright as the model goes, but has the sharp points you'd expect from such a path. The sinebow is darker at the secondary colors and more washed out in the primaries, and the katebow is using lack of brightness to make the colors more easily distinguishable.

[yomikoma]

And now that I consider it 3-dimensionally, the sinebow is a circle normal to the black-to-white line, as large as possible. It would be interesting to graph the katebow in 3d as well.

[cnoocy]

I was wondering what the others' shapes were.

[cnoocy]

It's more triangular than I expected: https://www.geogebra.org/3d/jkvgzfqw

[yomikoma]

Nice. Here's all 3 in their true shapes and sizes.