# Programmers of any language... need help

Discussion in 'OT Technology' started by kcarlson78, Apr 17, 2003.

1. ### kcarlson78Meanwhile, Jesus continued to shake his head in ex

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Ok.. this isn't language specific... I need an algorithm for plotting points on a circle given the center point (x,y) and the radius r, how do i generate a couple coordinates (x1,y1) pairs around the circle?

I'm writing a fireworks applet in java.. and it's all done.. except when my fireworks explode.. they're square.. I'd kinda like 'em to be round..

I soo feel like I should know this.. but can't seem to bring the information to the surface of my brain right now..

incase you're interested.. the project is here:
http://www.ourvillageidiots.com/fireworks/

2. ### Early ApexGuest

Okay, I think I've got it. Code below is Excel VBA, but can easily be adapted to any language.

To determine the x- and y-coordinates, use these formulas:

Where:

q = qth point of n
n = total number of points
j = circle center, x-axis
k = circel center, y-axis
Xq = x-coordinate for qth point
Yq = y-coordinate for qth point

The code in Excel VBA looks like this (I didn't clean up any of the parens...)

Code:
```Sub MakeACircle()
Dim n As Double
Dim x As Double
Dim y As Double
Dim j As Double
Dim k As Double
Dim r As Double
Dim q As Integer

r = 2
j = 5
k = 5

'This number controls gow many points the circle has
n = 30

For q = 1 To n
x = (r * (Cos(((q * 3.1415926535 * 360) / n) / 180))) + j
y = (r * (Sin(((q * 3.1415926535 * 360) / n) / 180))) + k

Cells(q + 1, 1) = x
Cells(q + 1, 2) = y
Next q

End Sub
```
The output, and a graph of it, looks like this:

Hope that helps!

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