Unity3D Quaternion LookRotation FromToRotation SetLookRotation
看到Quaternion的LookRotation函数，没看懂，就研究了一下。
public static Quaternion LookRotation(Vector3 forward, Vector3 upwards = Vector3.up);
Creates a rotation with the specified forward and upwards directions.
Returns the computed quaternion. If used to orient a Transform, the Z axis will be aligned with forward/ and the Y axis with upwards if these vectors are orthogonal. Logs an error if the forward direction is zero.
总结：其实说白了，LookRotation的含义就是，计算让Z轴对齐forward，让y轴对齐upward 所需要的旋转四元数。
参考链接：unity3D 彻底搞懂 Quaternion LookRotation FromToRotation SetLookRotation方法
https://docs.unity3d.com/ScriptReference/Quaternion.LookRotation.html