使用PCL进行可视化，但不会显示数据！我怎么解决这个问题？

Question

代码来自官方网站。我只使用PointXYZ类型的PCDFile，云中就有数据。这是我的代码：

int main() {

pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
if (-1 == pcl::io::loadPCDFile<pcl::PointXYZ>("to_shuidaoyezi.pcd", *cloud))
{
    std::cout << "无法读取PCD文件数据" << endl;
    return -1;
}   

std::cout << "Load " << cloud->width * cloud->height << " points from PCDFile" << endl;


pcl::visualization::CloudViewer viewer("Cloud Viewer");

//blocks until the cloud is actually rendered
viewer.showCloud(cloud);

//use the following functions to get access to the underlying more advanced/powerful
//PCLVisualizer

//This will only get called once
viewer.runOnVisualizationThreadOnce(viewerOneOff);

//This will get called once per visualization iteration
viewer.runOnVisualizationThread(viewerPsycho);
while (!viewer.wasStopped())
{
    //you can also do cool processing here
    //FIXME: Note that this is running in a separate thread from viewerPsycho
    //and you should guard against race conditions yourself...
    user_data++;
}
return 0;
}

有人知道如何解决这个问题吗？ 预先感谢！