这样x坐标在0到2a之间不断循环，转换式如下： x = (y < 0) ? 2*a-math.abs(x) :math.abs(x);
4．制作类
算法清楚后，把它写成类，方便以后使用。类如下：
class move { private var p = 2*math.pi;//数学中的2π private var c_x, c_y, c_a, c_b, nu, time:number; //依次为中心坐标(c_x, c_y)， 截距(c_a, c_b)，nu为mc的数目,time为弧度增量 private var obj:movieclip; //构造函数 public function move(x, y, a, b, n, t:number, o:movieclip) { c_x = x; c_y = y; c_a = a; c_b = b; nu = n; time = t; duplicate(o);//调用复制函数 } //得到和设置弧度的起始增量 public function get timer():number { return time; } public function set timer(t:number):void { time = t; } //得到和设置椭圆的中心x坐标 public function get cen_x():number { return c_x; } public function set cen_x(x:number):void { c_x = x; } //得到和设置椭圆的中心y坐标 public function get cen_y():number { return c_y; } public function set cen_y(y:number):void { c_y = y; } //得到和设置椭圆在x坐标轴上的截距 public function get cen_a():number { return c_a; } public function set cen_a(a:number):void { c_a = a; } //得到和设置椭圆在y坐标轴上的截距 public function get cen_b():number { return c_b; } public function set cen_b(b:number):void { c_b = b; } //得到和设置椭圆上mc的数目 public function get num():number { return nu; } public function set num(n:number):void { nu = n; } //设置mc的x坐标 public function set_x(radian:number):number { return math.cos(radian)*c_a+c_x; } //设置mc的y坐标 public function set_y(radian:number):number { return math.sin(radian)*c_b+c_y; } //复制，产生num个mc，并均匀分布 public function duplicate(obj:movieclip) { var j:number = 1; while (j<=num) { obj.duplicatemovieclip("a"+j, j); _root["a"+j].n = p/num*j; //每个mc的起始弧度值 _root["a"+j].gotoandstop(j);//mc跳到相应的帧 _root["a"+j]._x = set_x(p/num*j); _root["a"+j]._y = set_y(p/num*j);//计算坐标 j++; } } //mc的运动 public function mymove(obj:movieclip):void { obj._x = set_x(obj.n+time); obj._y = set_y(obj.n+time);//每个mc弧度等于起始弧度值加增量 time time = _xmouse>c_x ? time+0.005 : time-0.005; //根据鼠标位置确定旋转方向，0.005为旋转速度 } //坐标的转换 public function trans_x(obj:movieclip):number { var x:number = obj._x-c_x; var y:number = obj._y-c_y; //取得mc的坐标 x = (y<0) ? 2*c_a-math.abs(x) : math.abs(x);//转换 return x;//返回转换值 } //设置mc的透明度和深度 public function set_alpha(obj:movieclip):void { obj._alpha = trans_x(obj)/c_a*40+20;//从20到100 obj.swapdepths(trans_x(obj));//深度设置 } //设置mc的x方向的缩放 public function set_xscale(obj:movieclip):void { obj._xscale = trans_x(obj)/c_a*100-100;//从-100到100 obj.swapdepths(trans_x(obj)); } }
