unity3d 获取相机视口四个角的坐标

/// <summary>
    /// 获取指定距离下相机视口四个角的坐标
    /// </summary>
    /// <param name="cam"></param>
    /// <param name="distance">相对于相机的距离</param>
    /// <returns></returns>
    public static Vector3[] GetCameraFovPositionByDistance(this Camera cam, float distance)
    {
        Vector3[] corners = new Vector3[4];

        float halfFOV = (cam.fieldOfView * 0.5f) * Mathf.Deg2Rad;
        float aspect = cam.aspect;

        float height = distance * Mathf.Tan(halfFOV);
        float width = height * aspect;

        Transform tx = cam.transform;

        // 左上角
        corners[0] = tx.position - (tx.right * width);
        corners[0] += tx.up * height;
        corners[0] += tx.forward * distance;

        // 右上角
        corners[1] = tx.position + (tx.right * width);
        corners[1] += tx.up * height;
        corners[1] += tx.forward * distance;

        // 左下角
        corners[2] = tx.position - (tx.right * width);
        corners[2] -= tx.up * height;
        corners[2] += tx.forward * distance;

        // 右下角
        corners[3] = tx.position + (tx.right * width);
        corners[3] -= tx.up * height;
        corners[3] += tx.forward * distance;

        return corners;
    }