AS3碰撞检测类

众所周知，Adobe有一群懒散的工程师，所以adobe给as3提供的一些工具方法也就很具有欺骗性，今天我要给大家提供的是一个非常常用的功能。
碰撞检测，无论是游戏还是什么，都是很常见的，flash.display包下面的Display类中有个hitTestObject()的一个方法，简言之，这个东西检测矩形元件检测还不错，但是有多少图形是标准的矩形呢？所以今天我要给大家推荐一个很好的碰撞检测类：

package {

    import flash.display.BitmapData;
    import flash.display.BlendMode;
    import flash.display.DisplayObject;
    import flash.display.Sprite;
    import flash.geom.ColorTransform;
    import flash.geom.Matrix;
    import flash.geom.Point;
    import flash.geom.Rectangle;

    public class HitTest
    {

        public static function complexHitTestObject( target1:DisplayObject, target2:DisplayObject,  accurracy:Number = 1 ):Boolean
        {
            trace(complexIntersectionRectangle( target1, target2, accurracy ).width);

            return (complexIntersectionRectangle( target1, target2, accurracy ).width != 0);
        }

        public static function intersectionRectangle( target1:DisplayObject, target2:DisplayObject ):Rectangle
        {

            if( !target1.root || !target2.root || !target1.hitTestObject( target2 ) ) return new Rectangle();


            var bounds1:Rectangle = target1.getBounds( target1.root );
            var bounds2:Rectangle = target2.getBounds( target2.root );


            var intersection:Rectangle = new Rectangle();
            intersection.x   = Math.max( bounds1.x, bounds2.x );
            intersection.y    = Math.max( bounds1.y, bounds2.y);
            intersection.width      = Math.min( ( bounds1.x + bounds1.width ) - intersection.x, ( bounds2.x + bounds2.width ) - intersection.x );
            intersection.height = Math.min( ( bounds1.y + bounds1.height ) - intersection.y, ( bounds2.y + bounds2.height ) - intersection.y );

            return intersection;
        }

        public static function complexIntersectionRectangle( target1:DisplayObject, target2:DisplayObject, accurracy:Number = 1 ):Rectangle
        {                     
            if( accurracy <= 0 ) throw new Error( "ArgumentError: Error #5001: Invalid value for accurracy", 5001 );


            if( !target1.hitTestObject( target2 ) ) return new Rectangle();

            var hitRectangle:Rectangle = intersectionRectangle( target1, target2 );

            if( hitRectangle.width * accurracy <1 || hitRectangle.height * accurracy <1 ) return new Rectangle();

            var bitmapData:BitmapData = new BitmapData( hitRectangle.width * accurracy, hitRectangle.height * accurracy, false, 0x000000 ); 


            bitmapData.draw( target1, HitTest.getDrawMatrix( target1, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, -255, -255, 255 ) );

            bitmapData.draw( target2, HitTest.getDrawMatrix( target2, hitRectangle, accurracy ), new ColorTransform( 1, 1, 1, 1, 255, 255, 255, 255 ), BlendMode.DIFFERENCE );


            var intersection:Rectangle = bitmapData.getColorBoundsRect( 0xFFFFFFFF,0xFF00FFFF );

            bitmapData.dispose();


            if( accurracy != 1 )
            {
                intersection.x /= accurracy;
                intersection.y /= accurracy;
                intersection.width /= accurracy;
                intersection.height /= accurracy;
            }

            intersection.x += hitRectangle.x;
            intersection.y +=( hitRectangle.y);

            return intersection;
        }


        protected static function getDrawMatrix( target:DisplayObject, hitRectangle:Rectangle, accurracy:Number ):Matrix
        {
            var localToGlobal:Point;;
            var matrix:Matrix;

            var rootConcatenatedMatrix:Matrix = target.root.transform.concatenatedMatrix;

            localToGlobal = target.localToGlobal( new Point( ) );
            matrix = target.transform.concatenatedMatrix;
            matrix.tx = localToGlobal.x - hitRectangle.x;
            matrix.ty = localToGlobal.y - hitRectangle.y;

            matrix.a = matrix.a / rootConcatenatedMatrix.a;
            matrix.d = matrix.d / rootConcatenatedMatrix.d;
            if( accurracy != 1 ) matrix.scale( accurracy, accurracy );

            return matrix;
        }

    }

}