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

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

```On Wed, 2009-04-01 at 20:19 -0700, Bill Broadley wrote:
> Bill Kendrick wrote:
> > On Wed, Apr 01, 2009 at 10:37:37AM -0700, Harold Lee wrote:
> >>    Not sure if the formulas you've set out do this, but couldn't the rainbow
> >>    tool treat the difference between y coordinates as depth, the way that the
> >>    grass tool does? When y1 == y2, you get a semi-circle with the height ==
> >>    1/2 * abs(x2 - x1), i.e. the radius. Otherwise you get a rainbow with a
> >>    wider base at the point closer to the bottom of the screen that arcs back
> >>    to the other point.
> >
> > Neat idea, but I worry about kitchensinkness. :)
>
> How about doing it like xfig, it's really simple just 3 clicks, lets you do
> any kind of arc as you want, I can try it out on my 4 year old if ya want.
>

He uses the drag-click for the shape tool (drag to set the size and
aspect ratio, click afterwards to set the rotation), so he could use a
drag to set the end points, and a click to set the intermediate point
that the circle has to pass through. Fitting these points to a circle
would be pretty easy [just solve (x-x')^2+(y-y')^2=r^2 for x', y', and
for their curve tool.

If he wants to make the thickness configurable, he could introduce the
size slider used for the stamp tool for that.

--Ken

--
Chanoch (Ken) Bloom. PhD candidate. Linguistic Cognition Laboratory.
Department of Computer Science. Illinois Institute of Technology.
http://www.iit.edu/~kbloom1/

```

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