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create ellipse from line
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| durant 2006-09-15, 3:56 am |
| i am trying to find an awk solution to create the x,y points for an
ellipse drawn around a line.
the input will be two sets of XY values which will represent the axis
of the ellipse. it would be nice to have variables sch as maximum width
or total area for the ellipse.
i realize this is complicated, but i was just looking for an awk
solution since i am familiar with that.
thank you,
durant
durant_greenwood@sbcglobal.net
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| Ed Morton 2006-09-15, 3:56 am |
| durant wrote:
> i am trying to find an awk solution to create the x,y points for an
> ellipse drawn around a line.
>
> the input will be two sets of XY values which will represent the axis
> of the ellipse. it would be nice to have variables sch as maximum width
> or total area for the ellipse.
>
> i realize this is complicated, but i was just looking for an awk
> solution since i am familiar with that.
>
> thank you,
> durant
> durant_greenwood@sbcglobal.net
>
You may actually have better luck at the gnuplot NG
(comp.graphics.apps.gnuplot) since they use awk quite a bit for plotting
graphics.
Ed.
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durant wrote:
> i am trying to find an awk solution to create the x,y points for an
> ellipse drawn around a line.
>
> the input will be two sets of XY values which will represent the axis
> of the ellipse. it would be nice to have variables sch as maximum width
> or total area for the ellipse.
>
> i realize this is complicated, but i was just looking for an awk
> solution since i am familiar with that.
>
> thank you,
> durant
> durant_greenwood@sbcglobal.net
There is not enough information if you just give the endpoints of one
axis - you need both the major and minor axes.
If the major axis is parallel to the x axis, the equation is of the
form
((x-p)/a)^2 + ((y-q)/b)^2 = 1.
The points are of the form (p+a*cos(t), q+b*sin(t)), where t goes from
0 to 2*pi. There are various ways of parameterizing t to draw the
ellipse nicely.
If the major axis is not parallel, you have to rotate these points.
The problem is not in awk, it is in the math.
Martin Cohen
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