1.关于 2.1.0版本 Vector3 的疑问

如下：2.1.0的Vector3

        /**@private	*/
		public static const _ZERO:Vector3 =/*[STATIC SAFE]*/ new Vector3(0.0, 0.0, 0.0);
		/**@private	*/
		public static const _ONE:Vector3 =/*[STATIC SAFE]*/ new Vector3(1.0, 1.0, 1.0);
		/**@private	*/
		public static const _NegativeUnitX:Vector3 =/*[STATIC SAFE]*/ new Vector3(-1, 0, 0);
		/**@private	*/
		public static const _UnitX:Vector3 =/*[STATIC SAFE]*/ new Vector3(1, 0, 0);
		/**@private	*/
		public static const _UnitY:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 1, 0);
		/**@private	*/
		public static const _UnitZ:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, 1);
		/**@private	*/
		public static const _ForwardRH:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, -1);
		/**@private	*/
		public static const _ForwardLH:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, 1);
		/**@private	*/
		public static const _Up:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 1, 0);[/code][code]2.0.1 Vector3

        /**零向量，禁止修改*/
		public static const ZERO:Vector3 =/*[STATIC SAFE]*/ new Vector3(0.0, 0.0, 0.0);
		/**一向量，禁止修改*/
		public static const ONE:Vector3 =/*[STATIC SAFE]*/ new Vector3(1.0, 1.0, 1.0);
		/**X轴单位向量，禁止修改*/
		public static const NegativeUnitX:Vector3 =/*[STATIC SAFE]*/ new Vector3(-1, 0, 0);
		/**X轴单位向量，禁止修改*/
		public static const UnitX:Vector3 =/*[STATIC SAFE]*/ new Vector3(1, 0, 0);
		/**Y轴单位向量，禁止修改*/
		public static const UnitY:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 1, 0);
		/**Z轴单位向量，禁止修改*/
		public static const UnitZ:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, 1);
		/**右手坐标系统前向量，禁止修改*/
		public static const ForwardRH:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, -1);
		/**左手坐标系统前向量,禁止修改*/
		public static const ForwardLH:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 0, 1);
		/**上向量,禁止修改*/
		public static const Up:Vector3 =/*[STATIC SAFE]*/ new Vector3(0, 1, 0);

如图所示：Up 改成 _Up 这么改有什么特别意义么，如果我们升级引擎代码，只要用到的要全都改一遍，而且感觉不到有什么意义

2.Transform3D 里面
2.0.1里面的_forward，_up ,_right 这几个成员在2.1.0里面也被删掉了。这也感觉很奇怪，如果要获取forward变成了自己要在外部创建变量，o(╥﹏╥)o

        /** @private */
		private var _forward:Vector3 = new Vector3();
		/** @private */
		private var _up:Vector3 = new Vector3();
		/** @private */
		private var _right:Vector3 = new Vector3();
		/** @private */

能给解释一下，引擎组是怎么考虑的，然后才这么改么