Projecting Point to Axis

For final version please visit 
http://blog.yoz.sk/2010/11/4-000-000-rectangle-collisions-per-second/

by jozefchutka 16 Nov 2010

Embed

/**
 * Copyright jozefchutka ( http://wonderfl.net/user/jozefchutka )
 * MIT License ( http://www.opensource.org/licenses/mit-license.php )
 * Downloaded from: http://wonderfl.net/c/ap5F
 */

/*
For final version please visit 
http://blog.yoz.sk/2010/11/4-000-000-rectangle-collisions-per-second/
*/

package
{
    import flash.display.Shape;
    import flash.display.Sprite;
    import flash.display.StageAlign;
    import flash.display.StageScaleMode;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.geom.Point;
    import flash.text.TextField;
    
    [SWF(width="465", height="465", frameRate="30", backgroundColor="#FFFFFF")]
    public class WonderflApp extends Sprite
    {
        private var shape1:Shape = new Shape();
        private var rect1:Point = new Point(0, 0);
        private var rect1Width:uint = 100;
        private var rect1Height:uint = 50;
        private var r1p1:Point;
        private var r1p2:Point;
        private var r1p3:Point;
        private var r1p4:Point;
        
        private var shape2:Shape = new Shape();
        private var rect2:Point = new Point(0, 0);
        private var rect2Width:uint = 80;
        private var rect2Height:uint = 60;
        private var r2p1:Point;
        private var r2p2:Point;
        private var r2p3:Point;
        private var r2p4:Point;
        
        public function WonderflApp():void
        {
            stage.scaleMode = StageScaleMode.NO_SCALE;
            stage.align = StageAlign.TOP_LEFT;
            
            shape1.graphics.beginFill(0, 0);
            shape1.graphics.drawRect(rect1.x, rect1.y, rect1Width, rect1Height);
            shape1.x = 200;
            shape1.y = 100;
            shape1.rotation = 40;
            addChild(shape1);
            
            shape2.graphics.beginFill(0, 0);
            shape2.graphics.drawRect(rect2.x, rect2.y, rect2Width, rect2Height);
            shape2.rotation = 30;
            addChild(shape2);
            
            addEventListener(Event.ENTER_FRAME, onEnterFrame);
        }
        
        private function onEnterFrame(event:Event):void
        {
            graphics.clear();
            
            // rectangle 1
            shape1.rotation++;
            r1p1 = shape1.localToGlobal(rect1);
            r1p2 = shape1.localToGlobal(new Point(rect1.x + rect1Width, rect1.y));
            r1p3 = shape1.localToGlobal(new Point(rect1.x + rect1Width, rect1.y + rect1Height));
            r1p4 = shape1.localToGlobal(new Point(rect1.x, rect1.y + rect1Height));
            
            // rectangle 2
            shape2.x = mouseX;
            shape2.y = mouseY;
            r2p1 = shape2.localToGlobal(rect1);
            r2p2 = shape2.localToGlobal(new Point(rect2.x + rect2Width, rect2.y));
            r2p3 = shape2.localToGlobal(new Point(rect2.x + rect2Width, rect2.y + rect2Height));
            r2p4 = shape2.localToGlobal(new Point(rect2.x, rect2.y + rect2Height));
            
            // projections
            drawProjections(0xff0000, r1p1, r1p2, r2p1, r2p2, r2p3, r2p4);
        }
        
        private function drawProjections(color:uint,
            r1p1:Point, r1p2:Point, 
            r2p1:Point, r2p2:Point,
            r2p3:Point, r2p4:Point):void
        {
            var b1:Point = new Point(r1p1.x, r1p1.y);
            var b2:Point = new Point(r1p2.x, r1p2.y);
            
            graphics.lineStyle(2, color);
            graphics.moveTo(b1.x, b1.y);
            graphics.lineTo(b2.x, b2.y);
            
            graphics.lineStyle(0, color, 0.3);
            drawProjectionLine(b1, b2, r2p1);
        }
        
        private function drawProjectionLine(b1:Point, b2:Point, p:Point):void
        {
            graphics.moveTo(p.x, p.y);
            graphics.lineTo(
                Math2D.projectX(b1.x, b1.y, b2.x, b2.y, p.x, p.y), 
                Math2D.projectY(b1.x, b1.y, b2.x, b2.y, p.x, p.y));
        }
    }
}

    class Math2D
    {
        public function Math2D()
        {
        }
        
        public static function calcA(x1:Number, y1:Number, x2:Number, y2:Number)
            :Number
        {
            return (y1 - y2) / (x1 - x2);
        }
        
        public static function projectX(
            boundary1X:Number, boundary1Y:Number,
            boundary2X:Number, boundary2Y:Number,
            pointX:Number, pointY:Number):Number
        {
            if(boundary1X == boundary2X)
                return boundary1X;
            if(boundary1Y == boundary2Y)
                return pointX;
            var a:Number = calcA(boundary1X, boundary1Y, boundary2X, boundary2Y);
            return (pointY - boundary2Y + boundary2X * a + pointX / a) /
                   (a + 1 / a);
        }
        
        public static function projectY(
            boundary1X:Number, boundary1Y:Number,
            boundary2X:Number, boundary2Y:Number,
            pointX:Number, pointY:Number):Number
        {
            if(boundary1X == boundary2X)
                return pointY;
            if(boundary1Y == boundary2Y)
                return boundary1Y;
            var a:Number = calcA(boundary1X, boundary1Y, boundary2X, boundary2Y);
            var x:Number = projectX(boundary1X, boundary1Y,
                boundary2X, boundary2Y, pointX, pointY)
            return pointY + (pointX - x) / a;
        }
    }