unity3d 如何判断一点是不是在一个相机的视锥内

unity3d 如何判断一点是不是在一个相机的视锥内?

static public bool IsAPointInACamera(Camera cam, Vector3 wordPos)
{
    // 是否在视野内
    bool result1 = false;
    Vector3 posViewport = cam.WorldToViewportPoint(wordPos);
    Debug.Log("posViewport:" + posViewport.ToString());
    Rect rect = new Rect(0, 0, 1, 1);
    result1 = rect.Contains(posViewport);
    Debug.Log("result1:" + result1.ToString());
    // 是否在远近平面内
    bool result2 = false;
    if(posViewport.z >= cam.nearClipPlane && posViewport.z<=cam.farClipPlane)
    {
        result2 = true;
    }
    Debug.Log("result2:" + result2.ToString());
    // 综合判断
    bool result = result1 && result2;
    Debug.Log("result:" + result.ToString());
    return result;
}