Actionscript:
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/**
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Original function by Pieter Iserbyt:
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http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/DistancePoint.java
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from Paul Bourke's website:
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http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/
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*/
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function pointToLineDistance(p1:Sprite, p2:Sprite, p3:Sprite):Number {
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var xDelta:Number = p2.x - p1.x;
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var yDelta:Number = p2.y - p1.y;
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if ((xDelta == 0) && (yDelta == 0)) {
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// p1 and p2 cannot be the same point
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p2.x += 1;
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p2.y += 1;
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xDelta = 1;
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yDelta = 1;
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}
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var u:Number = ((p3.x - p1.x) * xDelta + (p3.y - p1.y) * yDelta) / (xDelta * xDelta + yDelta * yDelta);
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var closestPoint:Point;
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if (u <0) {
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closestPoint = new Point(p1.x, p1.y);
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} else if (u> 1) {
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closestPoint = new Point(p2.x, p2.y);
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} else {
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closestPoint = new Point(p1.x + u * xDelta, p1.y + u * yDelta);
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}
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return Point.distance(closestPoint, new Point(p3.x, p3.y));
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}
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/**
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Test out the function
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*/
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var dotA:Sprite = dot(100, 100);
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var dotB:Sprite = dot(200, 200);
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var dotC:Sprite = dot(150, 100, 0x0000FF);
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var txt:TextField = TextField(dotC.addChild(new TextField()));
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with(txt) x = 5, y = 5, autoSize = "left", selectable = false, mouseEnabled = false;
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addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
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graphics.clear();
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graphics.lineStyle(0,0x000000);
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graphics.moveTo(dotA.x, dotA.y);
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graphics.lineTo(dotB.x, dotB.y);
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txt.text = pointToLineDistance(dotA, dotB, dotC).toFixed(2);
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}
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// draggable dot
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function dot(xp:Number, yp:Number, col:uint = 0xFF0000, rad:Number=4):Sprite {
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var s:Sprite = Sprite(addChild(new Sprite));
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s.x = xp;
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s.y = yp;
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with(s.graphics) beginFill(col), drawCircle(0,0,rad);
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s.buttonMode = true;
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s.addEventListener(MouseEvent.MOUSE_DOWN, onDrag);
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return s;
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}
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function onDrag(evt:MouseEvent):void { evt.currentTarget.startDrag() }
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stage.addEventListener(MouseEvent.MOUSE_UP, onUp);
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function onUp(evt:MouseEvent):void{stopDrag() }
Last night I was working late and found myself in need of a way to calculate the distance between a point and a line. After a quick google search I found myself once again on Paul Bourke's extremely useful website. I was in a rush, so I just quickly ported the java code (by Pieter Iserbyt) and wrote this test snippet to make sure it works.
This code could be optimized a bit, but it works nicely.
I needed this for a commercial project, but as I was porting the code I thought of an interesting way to use this code to draw a gradient - may write and post that tomorrow.
5 Comments
this is not helpful at all
hey elisa, I assume your not an actionscript programmer - and were just looking for the math… and if thats the case this link should be helful:
http://local.wasp.uwa.edu.au/~pbourke/geometry/pointline/
Thanks for the code, it was really helpful, along with your line intersection code.
This was truly useful to me! It worked great!
Thanks! ^^
Thanks, its great.