鼠标拖动的同时绘制一块同等大小的区域：如下

using System.Collections;
using System.Collections.Generic;
using UnityEngine;
/// <summary>
/// 通过鼠标框选绘制矩形区域
/// </summary>
/// public enum MouseType
{left = 0,right = 1,middle = 2
}
public class DrawRectangleArea : MonoBehaviour
{bool _canAddArea = true;/// <summary>/// 是否可以绘制/// </summary>public bool canAddArea{set { _canAddArea = value; }get { return _canAddArea; }}bool _isDraw = false;[SerializeField]Transform areaCube;Vector3 leftTopPos = Vector3.zero;Vector3 rightBottomPos = Vector3.zero;/// <summary>/// 绘制区域所在的层级/// </summary>[SerializeField]LayerMask maskLayer = 0;//