unity 双指触摸放大缩小镜头 单指平移镜头

需要全场景观察模型和放大看模型局部细节的时候

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class CameraMove : MonoBehaviour
{
    //摄像机距离
    public float distance = 10.0f;
    //缩放系数
    public float scaleFactor = 1f;


    public float maxDistance = 30f;
    public float minDistance = 5f;


    //记录上一次手机触摸位置判断用户是在左放大还是缩小手势
    private Vector2 oldPosition1;
    private Vector2 oldPosition2;


    private Vector2 lastSingleTouchPosition;

    private Vector3 m_CameraOffset;
    private Camera m_Camera;

    public bool useMouse = true;

    //定义摄像机可以活动的范围
    public float xMin = -100;
    public float xMax = 100;
    public float zMin = -100;
    public float zMax = 100;

    //这个变量用来记录单指双指的变换
    private bool m_IsSingleFinger;

    //初始化游戏信息设置
    void Start()
    {
        m_Camera = this.GetComponent<Camera>();
        m_CameraOffset = m_Camera.transform.position;
    }

    void Update()
    {
        //判断触摸数量为单点触摸