package {
    public class Light {
        public var x:Number;
        public var y:Number;
        public var z:Number;
        private var _brightness:Number;
         
        public function Light(x:Number=-200,y:Number=-200,z:Number=-200,brightness:Number=1) {
            //light向量的空间坐标
            this.x = x;
            this.y = y;
            this.z = z;
            //亮度
            this.brightness = brightness;
        }
         
        public function set brightness(b:Number):void {
            //亮度值通常要求在0与1之间
            _brightness = Math.max(b,0);
            _brightness = Math.min(_brightness,1);
        }
         
        public function get brightness():Number {
            return _brightness;
        }
    }
}