Unity2D横板游戏之背景视差与无限滚动效果

简单介绍

背景视差效果。在 2D 横板游戏中，由若干个背景图片构成的背景，在背景移动的过程中，每一个背景图片的移动速度均不同，靠近玩家的背景图片移动速度快，而远离玩家的背景图片移动速度慢，从而形成背景的视差效果，使背景更加立体且富有层级。

背景无限滚动效果。背景无限滚动并不是在游戏场景中加载无限的背景，而是在水平方向上使用两个紧密相邻的背景进行交替渲染，从而形成无限滚动的错觉。

代码设计

public class BackgroundEffect : MonoBehaviour
{
    private Transform _follow;
    private GameObject _background1;
    private GameObject _background2;
    private float _backgroundWidth;
    private float _moveSpeed;
    private Vector2 _previousCameraPosition;

    public void Initialize(Transform follow, GameObject background1, GameObject background2, float moveSpeed)
    {
        _follow = follow;
        _background1 = background1;
        _background2 = background2;
        _moveSpeed = moveSpeed;
        _previousCameraPosition = _follow.position;
        SpriteRenderer spriteRenderer = _background1.GetComponent<SpriteRenderer>();
        if (spriteRenderer == null)
        {
            return;
        }
        Sprite sprite = spriteRenderer.sprite;
        Vector3 localScale = _background1.transform.localScale;
        _backgroundWidth = sprite.bounds.size.x * localScale.x;
        Vector3 background2Position = _background2.transform.position;
        background2Position = new Vector2(background2Position.x - _backgroundWidth, background2Position.y);
        _background2.transform.position = background2Position;
    }

    private void FixedUpdate()
    {
        Vector2 currentCameraPosition = _follow.position;
        Vector2 cameraOffset = currentCameraPosition - _previousCameraPosition;
        Vector3 backgroundPosition = _background1.transform.position;
        backgroundPosition = new Vector2(backgroundPosition.x + cameraOffset.x - cameraOffset.x * _moveSpeed, backgroundPosition.y + cameraOffset.y);
        _background1.transform.position = backgroundPosition;
        backgroundPosition = _background2.transform.position;
        backgroundPosition = new Vector2(backgroundPosition.x + cameraOffset.x - cameraOffset.x * _moveSpeed, backgroundPosition.y + cameraOffset.y);
        _background2.transform.position = backgroundPosition;
        if (_background1.transform.position.x <= _follow.position.x)
        {
            Vector3 background2Position = _background2.transform.position;
            background2Position = new Vector2(background2Position.x + 2f * _backgroundWidth, background2Position.y);
            _background2.transform.position = background2Position;
            (_background1, _background2) = (_background2, _background1);
        }
        if (_follow.position.x <= _background2.transform.position.x)
        {
            Vector3 background1Position = _background1.transform.position;
            background1Position = new Vector2(background1Position.x - 2f * _backgroundWidth, background1Position.y);
            _background1.transform.position = background1Position;
            (_background1, _background2) = (_background2, _background1);
        }
        _previousCameraPosition = currentCameraPosition;
    }
}

后记

由于个人能力有限，文中不免存在疏漏之处，恳求大家斧正，一起交流，共同进步。