[vox-tech] [OT] Math question: help me make a rainbow

[Bill Broadley]

> You seem to be trying to implement an algorithm that needs
> three points with only two inputs... you are bound to fail.

Well he seems to want exactly 180 degrees of a circle, so 2 points is fine.

3 would allow for any sub arc.

> One method I have seen is to click-drag-release to get the
> two endpoints and then interactively pick up the mouse position
> to track the height of the arc until a second click finishes
> the input. You would have to back out the actual radius of
> the circle if you needed it, but two inputs don't magically
> become three.

Yeah, I was thinking of a GUI that let you that displays a protractor
with 2 angles so you could an arbitrary fraction (0-100%) of a circle.
Then once that's done, allow for a thickness handle/knob.