效果

无限向上延伸的墙壁.gif

思路

将墙的位置设置到屏幕的左下角和右下角。
关注目标角色的PosY的变化，当达到合适的值（如当前墙高的一半时）时，修改墙的高度：

1. 外观图（Sprite Renderer）的Height变化（Tiled模式）
2. BoxCollider的OffsetY、SizeY的变化。

实现

1. 墙壁图的参数设置

   
   image.png

2. 配置墙壁

   
   左墙
   右墙

3. Wall的高度随目标角色的位置Y的变化而变化（代码控制）

   
   Walls.cs

4. 相机跟随（代码控制）

   
   Cam.cs

代码

Walls.cs

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

/// <summary>
/// 可无限向上延伸的墙壁
/// </summary>
public class Walls : MonoBehaviour
{
    [SerializeField]
    private Transform _refTrans;
    [SerializeField, Header("当refTrans的PosY达到高度的多少时，修改高度")]
    private float _changeHeightRatio = 0.5f;
    [SerializeField]
    private float _initHeight = 50;
    [SerializeField]
    private float _checkHeightInterval = 1f;
    [SerializeField]
    private Wall _leftWall;
    [SerializeField]
    private Wall _rightWall;

    private float CurHeight{ get; set; }

    private IEnumerator Start()
    {
        // 设置左右墙的位置：左下角、右下角
        var screenMinPos = Vector3.zero;
        var screenMaxPos = new Vector3(Screen.width, Screen.height, 0);
        var minPos = Camera.main.ScreenToWorldPoint(screenMinPos);
        var maxPos = Camera.main.ScreenToWorldPoint(screenMaxPos);
        _leftWall.SetPos(new Vector3(minPos.x, minPos.y, 0));
        _rightWall.SetPos(new Vector3(maxPos.x, minPos.y, 0));

        // 初始化高度
        SetHeight(_initHeight);

        // 每过一段时间检测一下，尝试修改高度
        while (true)
        {
            yield return new WaitForSeconds(_checkHeightInterval);
            if (_refTrans.position.y >= CurHeight * _changeHeightRatio)
            {
                SetHeight(CurHeight * 2);
            }
        }
    }

    private void SetHeight(float height)
    {
        _leftWall.SetHeight(height);
        _rightWall.SetHeight(height);
        CurHeight = height;
    }

    [System.Serializable]
    private class Wall
    {
        [SerializeField]
        private Transform _trans;
        [SerializeField]
        private SpriteRenderer[] _renderers;
        [SerializeField]
        private BoxCollider2D _col;

        public void SetPos(Vector3 pos)
        {
            _trans.position = pos;
        }

        public void SetHeight(float height)
        {
            if (_renderers != null && _renderers.Length > 0)
            { 
                for (int i = 0; i < _renderers.Length; i++)
                {
                    _renderers[i].size = new Vector2(_renderers[i].size.x, height);
                }
            }

            if (_col != null)
            {
                _col.size = new Vector2(_col.size.x, height);
                _col.offset = new Vector2(_col.offset.x, height / 2);
            }
        }
    }
}

Cam.cs

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

public class Cam : MonoBehaviour
{
    [SerializeField]
    private Transform _camTrans;
    [SerializeField]
    private Transform _target;
    [SerializeField]
    private float _posYOffset = 0f;
    [SerializeField]
    private float _moveSpeed = 5f;
    [SerializeField]
    private float _minPosY = 15;

    private void FixedUpdate()
    {
        _camTrans.transform.position = new Vector3(_camTrans.position.x, PosY, _camTrans.position.z);
    }

    private float PosY
    {
        get
        {
            return Mathf.Max(_minPosY, Mathf.Lerp(_camTrans.position.y, _target.position.y + _posYOffset, _moveSpeed * Time.fixedDeltaTime));
        }
    }
}