sorry i didn't want to submit the last voting. I didn't read the "relative to the PlotBox diagonal" at the time i was about to write a critic, but as i reread the description i closed the tab.
But i still think that this is an annoying feature, i would like it more if i could choose wether it should be relative or a fix size. I also don't like that it clears the axes. I know a workaround but it's still annoying me everytime i have to use arrow3. Just my opinion.
I'm surprised that you don't obtain a unique RGB value for a given wavelength, as your RGB functions are truncated, saturated at 1. For example, in the range 512-548 nm you have the same RGB value: a pure green 0-1-0. Also in the range 611-641 you give constant pure red 1-0-0. I guess the eye should perceive a difference along those ranges, so the results are not realistic. Correct?