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Circle drawing request. [message #7981]

Tue, 28 January 1997 00:00

D.Kennedy
Messages: 26
Registered: January 1997

Junior Member

This must be a FAQ - anyone got a good circle drawing sub-routine?
Input - x, y, radius
Output - [x,y] vectors for POLYFILL etc.

I have been using one (shown below) but I find it produces fine lines
shooting off to small y values from the left and right edges of each
circle. And my fiddling with it has made it worse I'm afraid.

FUNCTION CIRCLE, xcenter, ycenter, radius
; Emailed by Dfanning 27th Jan

step = (radius/24.0)
x = FLTARR(25)
y = FLTARR(25)

; Construct a circle

FOR j=0,24 DO BEGIN
x(j) = j*step
y(j) = SQRT(radius^2 - x(j)^2)
ENDFOR

x = [x, Reverse(x)]
y = [y, -Reverse(y)]
x = [-Reverse(x), x]
y = [y,y]

; Center the circle at the specified coordinates.

x = x + xcenter
y = y + ycenter

points = FLTARR(2, 100)
points(0,*) = x
points(1,*) = y
RETURN, points
END
--
David Kennedy, Dept. of Pure & Applied Physics, Queen's University of Belfast
Email: D.Kennedy@Queens-Belfast.ac.uk | URL: http://star.pst.qub.ac.uk/~dcjk/
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[Message index]

		Circle drawing request. By: D.Kennedy on Tue, 28 January 1997 00:00
		Re: Circle drawing request. By: Wayne Landsman on Tue, 28 January 1997 00:00

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