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;
//屏幕坐标
private Vector3 mScreenPoint;
//坐标偏移
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坐标
/**
* 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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