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.<br>
<br><div class="gmail_quote">On Tue, Mar 31, 2009 at 10:12 PM, Bill Broadley <span dir="ltr"><<a href="mailto:bill@cse.ucdavis.edu">bill@cse.ucdavis.edu</a>></span> wrote:<br><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
<div class="im">Bill Kendrick wrote:<br>
> On Tue, Mar 31, 2009 at 07:21:36PM -0700, Bill Broadley wrote:<br>
>> Some. Not sure what you are getting at though. You want to draw 180 degrees<br>
>> of a circle with the end points defined by p1 and p2? What if you want to<br>
>> make an upside down rainbow? Or 1/2 of one?<br>
><br>
> I only want to draw all 180 degress if y1==y2. Otherwise, it'd be<br>
> less of the arc. (See my ASCII diagrams)<br>
<br>
</div>Hrm, I don't think ascii is going to help, at least for me. Ah, ok, I have an<br>
idea of what you think you want to do. I think you do need 3 points. A<br>
center, radius, range of angles. Basically there are an infinite number of<br>
180 degree curves that go through 2 points, and there's no way to know how<br>
high the peak should be, nor which exact fraction of a circle to display.<br>
<br>
So for your diagrams how do you decide that in case 1 you do 1/2 a circle and<br>
the circle doesn't go above P2, but in case #3 you get 60% of a circle.<br>
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