xyY Cross-Section

Press start to generate the cross-sectional visual xyY gamut points.
It may take a minute or two, but only needs to be done one time.
And, depending on your browser, this tab must remain on top during the process; if you want to browse in the meantime, open a new window.

Choose an RGB color space, then move the slider to see cross-sections of the xyY gamut at the indicated Y value.
Press draw gamut to see the entire gamut.
At Y = 0, the corners of the gamut are the conventional RGB primaries; but, paradoxically, the colors are all black.
The gray outline is the visual xyY gamut.  Colors outside this range are not real.