Actionscript:
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// function found here:
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// http://www.alienryderflex.com/polygon/
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function pointInPolygon(x:Number, y:Number, polyX:Array, polyY:Array):Boolean{
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var j:int = polyX.length - 1;
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var oddNodes:Boolean = false;
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for (var i:int=0; i <polyX.length; i++) {
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if (polyY[i] <y && polyY[j]>= y || polyY[j] <y && polyY[i]>= y) {
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if (polyX[i] + (y - polyY[i]) / (polyY[j] - polyY[i]) * (polyX[j] - polyX[i]) <x) {
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oddNodes = !oddNodes;
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}
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}
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j = i;
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}
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return oddNodes;
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}
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// draw an overly complex poly and store all x y coords
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var pX:Array= new Array();
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var pY:Array = new Array();
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graphics.beginFill(0xCC0000);
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for (var i:int = 0; i<60; i++){
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pX[i] = Math.random()*stage.stageWidth;
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pY[i] =Math.random()*stage.stageHeight;
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if (i == 0){
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graphics.moveTo(pX[i], pY[i]);
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}else{
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graphics.lineTo(pX[i], pY[i]);
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}
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}
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addEventListener(Event.ENTER_FRAME, onLoop);
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function onLoop(evt:Event):void {
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alpha = 1;
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if (pointInPolygon(mouseX, mouseY, pX, pY)){
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alpha = .5;
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}
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}
This snippet shows how to test to see if a point is inside a polygon. This may not really be useful as hitTestPoint() is likely faster - however this could be modified for other purposes such as polygon to polygon collision. This algorithm works nicely on all kinds of polygons ... convex, concave etc...
I found this algorithm in an article by Darel Rex Finley ... here.
I've used this function in Processing a few times...
2 Comments
I love u!
Btw, is there a way to get intersection point?
thanks. I think this post might help with intersections.
http://actionsnippet.com/?p=956