>> Also it would be surprising to me if the
>> human visual range came out exactly as a cylinder (after a brief glance
>> of the maths involved), are you sure about this?
>>
>
> The human visual range has a very irregular shape.
>
> https://en.wikipedia.org/wiki/File:Cie_Chart_with_sRGB_gamut_by_spigget.png
>
> There's a lot of blank empty space around it in every color space. (The
> one in the picture is called CIExyY I think.
>
> I would like to learn how to plot this irregular shape in the near future.

You just need the XYZ colour-matching functions in terms of wavelength. 
Look here (just click the first "Submit" to get a basic table):

http://cvrl.ioo.ucl.ac.uk/cmfs.htm

This table then gives you the exact XYZ values for each pure wavelength. 
XYZ is a linear representation of absolute colour, so you can do a lot 
of math with them (eg adding, averaging, mixing etc).

To get the graph you linked to, you just need to calculate x and y for 
each of those wavelengths.

x = X/(X+Y+Z)
y = Y/(X+Y+Z)

You'll then find that the x,y pairs give the outline of the graph you 
linked to, which are the pure wavelengths. The internal area is formed 
by mixing pure wavelengths, so roughly speaking the further you are away 
from the boundary the more "wideband" the light is.

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