旋转插值运算

// 摘要:
//     Creates a rotation with the specified forward and upwards directions.
//
// 参数:
//   forward:
//     The direction to look in.
//
//   upwards:
//     The vector that defines in which direction up is.

例子：

using UnityEngine;
using System.Collections;
/*
* 
*/
public class ExampleClass : MonoBehaviour {
    public Transform player;
    public Transform target;
    void Update() {
          Vector3 relativePos = target.position - player.position;
          //relativePos.y = 0;//player物体朝向target物体时默认y轴会有倾斜，如果不想倾斜，可设置y轴坐标为0
          player.rotation = Quaternion.LookRotation(relativePos);
    }
}

**仅仅使用Quaternion中的LookRotation方法，可以使当前物体在一瞬间就朝向目标物体。假使要物体慢慢旋转朝向目标物体，就需要再加上插值运算：

Quaternion.Lerp或者Quaternion.Slerp

using UnityEngine;
using System.Collec