Closest Point on a Line

Actionscript:
  1. // from
  2. // http://www.gamedev.net/topic/444154-closest-point-on-a-line/
  3.  
  4. function getClosestPoint(A:*, B:*, P:*, segmentClamp:Boolean=true):Point {
  5.     var AP:Point = new Point(P.x - A.x, P.y - A.y),
  6.         AB:Point = new Point(B.x - A.x, B.y - A.y);
  7.     var ab2:Number=AB.x*AB.x+AB.y*AB.y;
  8.     var ap_ab:Number=AP.x*AB.x+AP.y*AB.y;
  9.     var t:Number=ap_ab/ab2;
  10.     if (segmentClamp) {
  11.         if (t<0.0) {
  12.             t=0.0;
  13.         } else if (t> 1.0) {
  14.             t=1.0;
  15.         }
  16.  
  17.     }
  18.     return new Point(A.x + AB.x * t, A.y + AB.y * t);
  19. }
  20.  
  21.  
  22. var point:Sprite = Sprite(addChild(new Sprite()));
  23. point.x = 50;
  24. point.y = 50;
  25. with(point.graphics) beginFill(0), drawCircle(0,0, 3);
  26.  
  27. var line:MovieClip = MovieClip(addChild(new MovieClip()));
  28. line.a = new Point(20, 100);
  29. line.b = new Point(300, 60);
  30. with(line.graphics) lineStyle(0), moveTo(line.a.x, line.a.y), lineTo(line.b.x, line.b.y);
  31.  
  32. var closestPoint:Point = getClosestPoint(line.a, line.b, point);
  33.  
  34. var closest:Sprite = Sprite(addChild(new Sprite()));
  35. closest.x = closestPoint.x;
  36. closest.y = closestPoint.y;
  37. with(closest.graphics) beginFill(0xFF0000), drawCircle(0,0, 3);

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