in reply to Re: Creating a circle in a data structure
in thread Creating a circle in a data structure

When using the whole disc, it works nicely. The individual points do not work, unfortunately.

I can use the whole disc method, but I need to be able to calculate the distance from the center of the circle. I've tried many formulas, and some look close (working for x values or y values), but nothing actually works.

  • Comment on Re^2: Creating a circle in a data structure

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Re^3: Creating a circle in a data structure
by Crackers2 (Parson) on May 29, 2007 at 03:08 UTC

    Yes you're right. To complete the outline you have to connect each point to the previous point. Something like this:

    $prevdist = 0;

foreach $ydist ( 0..$radius ) {
  # using the formula:
  # xdist*xdist + ydist*ydist = radius*radius
  $newxdist = int(sqrt( $radius*$radius - $ydist*$ydist));

  # Take advantage of symmetry to plot 4 lines at once
  # (for circle outline, draw a line from the previous
  # point to the new one)
  foreach $xdist ($prevdist..$newxdist) {
    $circle{$x_center-$xdist}{$y_center-$ydist}++;
    $circle{$x_center+$xdist}{$y_center-$ydist}++;
    $circle{$x_center-$xdist}{$y_center+$ydist}++;
    $circle{$x_center+$xdist}{$y_center+$ydist}++;
  }

  $prevdist = $newxdist;
}

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