using UnityEngine;

public class LimitedBillboard : MonoBehaviour
{
    public Camera targetCamera;

    [Header("Y轴（左右）限制")]
    public float minYAngle = -45f;
    public float maxYAngle = 45f;

    [Header("X轴（上下）限制")]
    public float minXAngle = -20f;
    public float maxXAngle = 20f;

    private Vector3 initialForward;

    void Start()
    {
        if (targetCamera == null)
            targetCamera = Camera.main;

        // 记录初始朝向（用于相对旋转）
        initialForward = transform.forward;
    }

    void Update()
    {
        if (targetCamera == null) return;

        Vector3 directionToCamera = targetCamera.transform.position - transform.position;

        // 计算相对方向
        Quaternion lookRotation = Quaternion.LookRotation(directionToCamera);
        Vector3 targetEuler = lookRotation.eulerAngles;

        // 处理角度跨越360°的情况（转换为 -180 ~ 180）
        float yAngle = Mathf.DeltaAngle(0f, targetEuler.y - transform.eulerAngles.y);
        float xAngle = Mathf.DeltaAngle(0f, targetEuler.x - transform.eulerAngles.x);

        // 限制角度
        yAngle = Mathf.Clamp(yAngle, minYAngle, maxYAngle);
        xAngle = Mathf.Clamp(xAngle, minXAngle, maxXAngle);

        // 应用角度（保留当前本地角度，只改X和Y）
        Vector3 currentEuler = transform.eulerAngles;
        currentEuler.y += yAngle;
        currentEuler.x += xAngle;

        transform.eulerAngles = currentEuler;
    }
}