Animation简介
Unity提供的动画系统的主要功能：
retargetable animations：重定向动画 full control of animation weights at runtime： runtime控制动画的权重 event calling from within the animation playback ：动画播放途中调用event sophisticated state machine hierarchies and transitions：精妙的动画状态机，包括hierarchy和transition blend shapes for facial animations：用于面部动画的blend shape and much more retargetable animat
