PCL学习笔记（2）：点云视窗类CloudViewer的介绍以及PCL程序：代码解析

点云视窗类CloudViewer是简单显示点云的可视化工具类，可以让用户用尽可能少的代码查看点云。注意：点云视窗类不能应用于多线程应用程序中。

有关CloudViewer类的成员变量和函数等等，可以在C:\Program Files\PCL 1.6.0\include\pcl-1.6\pcl\visualization\impl目录下的pcl_visualizer.hpp文件中查看。

/* 

    *PCL安装和环境配置请参考：

   *http://blog.csdn.net/chentravelling/article/details/43451589

   *代码出处：

   *http://www.pclcn.org/study/shownews.php?lang=cn&id=149

    *代码中加载的点云文件 my_point_cloud.pcd，可以去下面地址复制粘贴：

    *http://blog.csdn.net/chentravelling/article/details/43451589

*/

//以下笔记于2015年2月5日修正：

一、PCL程序：

#include <pcl/visualization/cloud_viewer.h>
#include <iostream>
#include <pcl/io/io.h>
#include <pcl/io/pcd_io.h>

int user_data;

void viewerOneOff (pcl::visualization::PCLVisualizer& viewer)
{
	//设置背景颜色
    viewer.setBackgroundColor (1.0, 0.5, 1.0);
	//球体坐标
    pcl::PointXYZ o;
    o.x = 0;
    o.y = 0;
    o.z = 0;
	//添加球体
    viewer.addSphere (o, 1, "sphere", 0);
    std::cout << "i only run once" << std::endl;

}

void viewerPsycho (pcl::visualization::PCLVisualizer& viewer)
{
    static unsigned count = 0;
    std::stringstream ss;
    ss << "Once per viewer loop: " << count++;
    viewer.removeShape ("text", 0);
    viewer.addText (ss.str(), 200, 300, "text", 0);

    //FIXME: possible race condition here:
    user_data++;
}

int main ()
{
    pcl::PointCloud<pcl::PointXYZRGBA>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZRGBA>);
    pcl::io::loadPCDFile ("my_point_cloud.pcd", *cloud); //加载点云文件

    pcl::visualization::CloudViewer viewer("Cloud Viewer");//创建viewer对象

    

    //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;
}

二、代码解析

void viewerOneOff (pcl::visualization::PCLVisualizer& viewer)//该函数功能是设置viewer信息
{
	//设置背景颜色
    viewer.setBackgroundColor (1.0, 0.5, 1.0);
	//添加球体
    viewer.addSphere (o, 1, "sphere", 0);

}

1.viewer.addSphere ()才是添加一个球体，第二个参数1是半径，第四个参数置0可见，置1不可见。初学者可能会误以为，程序运行后的球体是程序后面部分加载的点云文件里的点所构成，其实不是的。

2.pcl::io::loadPCDFile ("my_point_cloud.pcd", *cloud); 加载工程目录下my_point_cloud.pcd文件，该文件中的三维点，描绘的其实是point cloud library 的logo,见下图。【请仔细看~~~！】


如果我们不调用viewer.addSphere ()，运行结果就会是：就非常好看了。


PCD文件的格式说明可参考http://www.pclcn.org/study/shownews.php?lang=cn&id=54


3.同时有球体和logo的图，半径=5。


如果我们只是注释掉setBackgroundColor这一句，效果如下图：


建立my_point_cloud.pcd文件，请点击http://blog.csdn.net/chentravelling/article/details/43451589

文件数据内容附在下边：

<span style="font-size:14px;"><span style="font-size:14px;"># .PCD v.7 - Point Cloud Data file format  
VERSION .7  
FIELDS x y z rgb  
SIZE 4 4 4 4  
TYPE F F F F  
COUNT 1 1 1 1  
WIDTH 213  
HEIGHT 1  
VIEWPOINT 0 0 0 1 0 0 0  
POINTS 213  
DATA ascii  
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