超高效的不规则物体碰撞检测

之前，在坛里看到过有朋友贴过不规则物体碰撞检测的类，这里，我再贴个一位牛老外写的一个类，经自己测试，用一个1500*1500的矢量图和一个 10*10的不短移动的小球进行碰状检测，CPU占用仅4%左右，超级高效！！！
这里是代码：
Actionscript:

package ws.tink.display

{



        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

                {

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

                }



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

                {

                        // If either of the items don't have a reference to stage, then they are not in a display list

                        // or if a simple hitTestObject is false, they cannot be intersecting.

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



                        // Get the bounds of each DisplayObject.

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

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



                        // Determine test area boundaries.

                        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 a simple hitTestObject is false, they cannot be intersecting.

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



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

                        // If their boundaries are no interesecting, they cannot be intersecting.

                        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 );



                        // Draw the first target.

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

                        // Overlay the second target.

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



                        // Find the intersection.

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



                        bitmapData.dispose();



                        // Alter width and positions to compensate for accurracy

                        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;

                }



        }



}