【Unity2D】背景分层实现

        2D游戏如果只有一层背景显得比较单调，为了提现更强的空间感，可以通过添加多个背景层，并且让背景层随着角色的移动而缓慢移动，距离近的背景层移动较快，反之移动较慢。代码实现如下：

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

public class LayeringBackground : MonoBehaviour
{
    private void Awake()
    {
        _cam = Camera.main.transform;
    }

    void Start()
    {
        _preCamPos = _cam.position;

        _parralaxScales = new float[_backgrounds.Length];
        for(int i = 0; i < _parralaxScales.Length; ++i)
        {
            _parralaxScales[i] = Mathf.Pow(_bgMoveScaleFactor, i + 1);
        }

        // 判断背景是否作为了相机的子物体
        _bFollowCamera = new bool[_backgrounds.Length];
        for(int i = 0; i < _backgrounds.Length; ++i)
        {
            if (_cam == _backgrounds[i].parent)
                _bFollowCamera[i] = true;
            else
                _bFollowCamera[i] = false;
        }
    }

    void Update()
    {
        for(int i = 0; i < _backgrounds.Length; ++i)
        {
            float offsetX = (_preCamPos.x - _cam.position.x) * _parralaxScales[i];
            Vector3 offset2Camera = _cam.position - _preCamPos;
            var targetPos = _backgrounds[i].position;

            // 背景跟随相机移动
            if (!_bFollowCamera[i])
            {
                targetPos += offset2Camera;
            }
            targetPos.x += offsetX;
            _backgrounds[i].position = targetPos;
        }

        _preCamPos = _cam.position;
    }

    [Header("前面的移动快，后面的移动慢")]
    public Transform[] _backgrounds;
    public float _bgMoveScaleFactor = 0.25f;

    float[] _parralaxScales;
    private Transform _cam;
    private Vector3 _preCamPos;
    bool[] _bFollowCamera;
}

效果图：

不同背景层的移动速度不同。