自由视角摄像机，实现旋转，缩放

借鉴前人代码，自己加了一些注释，帮助大家理解

操作方式：
1.新建一个脚本：CameraControl.cs
2.把脚本绑定到摄像机上
代码如下：（注释很详细）

using UnityEngine;
using System.Collections;

public class CameraControl : MonoBehaviour
{
	//观察目标
	public Transform Target;

	//观察距离
	public float Distance = 5F;

	//旋转速度
	private float SpeedX = 240;
	private float SpeedY = 120;

	//角度限制
	private float MinLimitY = -20;
	private float MaxLimitY = 80;

	//旋转角度
	private float mX = 0.0F;
	private float mY = 0.0F;

	//鼠标缩放距离最值
	private float MaxDistance = 10;
	private float MinDistance = 1.5F;
	//鼠标缩放速率
	private float ZoomSpeed = 2F;

	//是否启用差值
	public bool isNeedDamping = true;
	//速度
	public float Damping = 10F;

	//存储角度的四元数
	private Quaternion mRotation;

	//定义鼠标按键枚举
	private enum MouseButton
	{
		//鼠标左键
		MouseButton_Left = 0,
		//鼠标右键
		MouseButton_Right = 1,
		//鼠标中键
		MouseButton_Midle = 2
	}

	//相机移动速度
	private float MoveSpeed = 5.0F;
	//屏幕座标
	private Vector3 mScreenPoint;
	//座标偏移
	private Vector3 mOffset;

	void Start ()
	{  
		//初始化旋转角度  
		mX = transform.eulerAngles.x;  
		mY = transform.eulerAngles.y;  
	}

	void LateUpdate ()
	{  
		//鼠标右键旋转  
		if (Target != null && Input.GetMouseButton ((int)MouseButton.MouseButton_Right)) {  
			//获取鼠标输入  
			mX += Input.GetAxis ("Mouse X") * SpeedX * 0.02F;  
			mY -= Input.GetAxis ("Mouse Y") * SpeedY * 0.02F;  
			//范围限制
			mY = ClampAngle (mY, MinLimitY, MaxLimitY);  
			//计算旋转（按照X，Y，Z轴进行旋转，分别旋转 mX,mY,0度）
			mRotation = Quaternion.Euler (mY, mX, 0);  
			//根据是否插值采取不同的角度计算方式  
			if (isNeedDamping) {  
				transform.rotation = Quaternion.Lerp (transform.rotation, mRotation, Time.deltaTime * Damping);
			} else {  
				transform.rotation = mRotation;  
			}  
		}  

		//鼠标中键平移  


		//鼠标滚轮缩放  
		Distance -= Input.GetAxis ("Mouse ScrollWheel") * ZoomSpeed;  
		Distance = Mathf.Clamp (Distance, MinDistance, MaxDistance);  

		//重新计算摄像机的位置 （Vector3 (0.0F, 0.0F, -8)为方向向量） 叉乘代表旋转后的相对座标
		/**
		 * detail:
		 * Quaternion quaternion = Quaternion.Euler(new Vector3(0, 90, 0)); --代表根据Y轴旋转90度
		 * vec = new Vector3(0, 1, 0);
		 * vec2 = quaternion * vec;  --quaternion 左乘 vec, 返回 向量 vec 旋转 quaternion 后的向量
		 * 
		 */
		Vector3 mPosition = mRotation * new Vector3 (0.0F, 0.0F, -Distance) + Target.position;  

		//设置相机的位置  
		if (isNeedDamping) {  
			transform.position = Vector3.Lerp (transform.position, mPosition, Time.deltaTime * Damping);   
		} else {  
			transform.position = mPosition;  
		}  

	}


	//角度限制
	private float  ClampAngle (float angle, float min, float max)
	{  
		if (angle < -360)
			angle += 360;  
		if (angle > 360)
			angle -= 360;  
		/**
		 * Clamp 作用：范围控制
		 * 如果angle<min ->angle=min   如果angle>max angle=max 如果 min<=angle<=max  angle = angle
		 */
		return Mathf.Clamp (angle, min, max);  
	}
}

有什么问题欢迎大家来交流
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