Unity 判断物体是否在相机前面以及UI跟随3D物体

    /// <summary>
    /// 判断物体的坐标是否在相机前方
    /// </summary>
    /// <param name="worldPos"></param>
    /// <returns></returns>
    public bool IsInView(Vector3 worldPos)
    {
        Transform camTransform = Camera.main.transform;
        Vector2 viewPos = Camera.main.WorldToViewportPoint(worldPos);
        Vector3 dir = (worldPos - camTransform.position).normalized;
        float dot = Vector3.Dot(camTransform.forward, dir);//判断物体是否在相机前面
        if (dot > 0 && viewPos.x >= 0 && viewPos.x <= 1 && viewPos.y >= 0 && viewPos.y <= 1)
            return true;
        else
            return false;
    }


    /// <summary>
    /// 3D坐标转UI坐标
    /// </summary>
    /// <param name="position"></param>
    /// <returns></returns>
    public static Vector2 WorldToUgui(Vector3 position)
    {

        Vector2 screenPoint = Camera.main.WorldToScreenPoint(position);//世界坐标转换为屏幕坐标
        Vector2 anchorPos = Vector2.zero;
        //UI设置为Screen Space - Camera 模式 然后设置一个UI相机
        RectTransformUtility.ScreenPointToLocalPointInRectangle(Canvas.transform as RectTransform, screenPoint,Canvas.worldCamera, out anchorPos);
        return anchorPos;
    }

具体使用案例：

 void Update()
    {
        for (int i = 0; i < marker3Ds.Count; i++) //持有一个3d物体List,每帧遍历
        {
            if (marker3Ds[i].MarkerUI != null) //物体上持有对应UI
            {
                if (IsInView(marker3Ds[i].transform.position))
                {
                    marker3Ds[i].MarkerUI.gameObject.SetActive(true);
                    ((RectTransform)marker3Ds[i].MarkerUI.transform).anchoredPosition = WorldToUgui(marker3Ds[i].transform.position);
                }
                else
                {
                    marker3Ds[i].MarkerUI.gameObject.SetActive(false); //避免相机后面物体UI显示在屏幕上
                }
            }
        }
    }