参考：
https://answers.unity.com/questions/186252/multiply-quaternion-by-vector.html
总结：Quaternion * Vector3 表示在世界坐标系下，Vector3的任意旋转；
In the quaternion world, multiplication is the way to apply the rotation to something 【在Quaternion下，相乘表示应用旋转】
Quaternion.Inverse(quaternion) returns the inverse rotation
The vector will be rotated in the world space. The quaternion actually represents a single rotation of some angle around an arbitrary axis (not necessarily XYZ), but this axis is relative to the world. If a more complex rotation is specified - like Euler(15, 45, 60), for instance - Unity converts it to a single rotation: the equivalent axis and angle are calculated and encoded in the quaternion format.【世界坐标系的旋转，相当于： 四元数实际上表示围绕任意轴（不一定是XYZ）的某个角度的单个旋转】
标签：相乘,Vector3,unity,quaternion,rotation,Quaternion,axis From： https://www.cnblogs.com/sun-shadow/p/17274193.html