Flash中使用ActionScript检测圆形和矩形是否碰撞（倾斜矩形）

思路：

1、首先将圆的中心点，都转换为以矩形的边为X/Y的坐标系；

2、做AABB矩形和圆的相交检测；

 

代码如下：

        /**

         * 将一个点,按照指定的坐标信息(原点,旋转),转换为另外一个点 

         * @param p 原始点

         * @param base 新的坐标原点

         * @param angle 新左边系X轴的旋转角度

         * @return 新点的数据 

         * 

         */

        public static function convertLocalPoint(p:Point, base:Point, angle:Number):Point

        {

            var matrix :Matrix = new Matrix();

            //matrix.createBox(1, 1, -angle*Math.PI/180, -base.x, -base.y);

            matrix.translate(-base.x, -base.y);

            matrix.rotate(-angle*Math.PI/180);

            var p2 :Point = matrix.transformPoint(p);

            return p2;

        }

        

        /**

         * 判定一个圆形，是否和矩形相交（矩形的边和XY坐标轴对齐） 

         * @param center

         * @param radius

         * @param min

         * @param max

         * @return 

         * 

         */

        public static function intersectCircleAABB(center:Point, radius:Number, min:Point, max:Point) : Point

        {

            var closestPoint:Point = center.clone();

            if( center.x < min.x )

                closestPoint.x = min.x;

            else if( center.x > max.x )

                closestPoint.x = max.x;

            if( center.y < min.y )

                closestPoint.y = min.y;

            else if( center.y > max.y )

                closestPoint.y = max.y;

            var diff:Point = closestPoint.subtract( center );

            if( diff.x * diff.x + diff.y * diff.y > radius * radius )

                return null;

            return closestPoint;

        }          

        

        /**

         * 判定一个圆和一个矩形是否碰撞 

         * @param center

         * @param radius

         * @param loc

         * @param angle

         * @param width

         * @param height

         * @return true/碰撞 false/不碰撞 

         * 

         */

        public static function checkRectCircleCollide(center:Point, radius:Number, loc:Point, angle:Number, width:Number, height:Number):Boolean

        {

            var min        :Point = new Point(0, -height/2);

            var max        :Point = new Point(width, height/2);

            trace('center:', center, 'radius:', radius, 'loc:', loc, 'angle:', angle, 'width:', width, 'height:', height);

            var center2    :Point    = convertLocalPoint(center, loc, angle);

            var result    :Point = intersectCircleAABB(center2, radius, min, max);

            trace('center2:', center2, 'min:', min, 'max:', max);

            return result!=null;

        }

        

测试代码：

        [Test]

        public function testMatrix():void

        {

            var base :Point = new Point(0,0);

            var angle :Number = 7.454;

            var p    :Point = new Point(137, 14);

            var p1  :Point = Vector2Extension.convertLocalPoint(p, base, angle);

            trace("p", p, "p1", p1);



            base = new Point(2266,2049);

            angle = 7.454;

            p    = new Point(2403, 2063);

            p1  = Vector2Extension.convertLocalPoint(p, base, angle);

            trace("p", p, "p1", p1);

            

            var p2 :Point = Vector2Extension.intersectCircleAABB(new Point(500,500), 142, new Point(10,10), new Point(900,900));

            trace(p2);

            

            

        }