Point cloud study notes 16 - pcl point cloud visualization

Visualization is the theory, method and technology of using computer graphics and image processing technology to convert data into graphics or images and display them on the screen and interactively process them.

The pcl_visualization library in PCL provides visualization-related data structures and components, which are mainly used to visualize the results processed by other module algorithms, which can be fed back to users intuitively. It relies on pcl_common, pcl_range_image, pcl_kdtree, pcl_IO modules and VTK external open source visualization libraries. Two commonly used visualization classes are given below.

类一：pcl::visualization::PCLVisualizer

PCLVisualizer is PCL's main class for visualizing 3D point clouds. Its internal realization of adding various 3D objects and the realization of interaction, etc., is more complete than other classes.

Basic display functions: display point cloud, grid, set color, connect line

#include <pcl/io/pcd_io.h>
#include <pcl/io/ply_io.h>
#include <pcl/point_types.h>
// 包含相关头文件
#include <pcl/visualization/pcl_visualizer.h>

typedef pcl::PointXYZ PointT;

int main()
{
    
    
	// 读取点云
	pcl::PointCloud<PointT>::Ptr cloud1(new pcl::PointCloud<PointT>);
	pcl::io::loadPCDFile("0010.pcd", *cloud1);

	pcl::PointCloud<PointT>::Ptr cloud2(new pcl::PointCloud<PointT>);
	pcl::io::loadPCDFile("0020.pcd", *cloud2);

	// 定义对象
	pcl::visualization::PCLVisualizer viewer; 
	//设置背景颜色，默认黑色
	//viewer.setBackgroundColor(100, 100, 100); // rgb

	// --- 显示点云数据 ----
	// "cloud1" 为显示id，默认cloud,显示多个点云时用默认会报警告。
	pcl::visualization::PointCloudColorHandlerCustom<PointT> green(cloud2, 0, 255, 0); // rgb
	viewer.addPointCloud(cloud1, green, "cloud1"); 

	pcl::visualization::PointCloudColorHandlerCustom<PointT> red(cloud2, 255, 0, 0); // rgb
	// 将点云设置颜色，默认白色
	viewer.addPointCloud(cloud2, red, "cloud2");

	// 将两个点连线
	PointT temp1 = cloud1->points[0];
	PointT temp2 = cloud1->points[1000];
	//viewer.addLine(temp1, temp2, "line0"); 
	// 同样可以设置线的颜色，蓝色
	viewer.addLine(temp1, temp2, 0, 0, 255, "line0");

	// --- 显示网格数据 ---
	pcl::PolygonMesh mesh;
	pcl::io::loadPLYFile("read.ply", mesh);

	viewer.addPolygonMesh(mesh);


	// 开始显示2种方法,任选其一
	// 1. 阻塞式
	viewer.spin();

	// 2. 非阻塞式
	while (!viewer.wasStopped())
	{
    
    
		viewer.spinOnce(100);
		boost::this_thread::sleep(boost::posix_time::microseconds(100000));
		// 可添加其他操作
	}

	system("pause");
	return 0;
}

renderings

Advanced features: set the callback function for interaction, display area segmentation

key event

#include <pcl/io/pcd_io.h>
#include <pcl/visualization/pcl_visualizer.h>

// 回掉函数所用数据结构
struct callback_args {
    
    
	bool *isShow;
	pcl::PointCloud<pcl::PointXYZ>::Ptr orgin_points;
	pcl::visualization::PCLVisualizer::Ptr viewerPtr;
};

// 按键事件回掉函数
void kb_callback(const pcl::visualization::KeyboardEvent& event, void* args)
{
    
    
	if (event.keyDown() && event.getKeyCode() == 'a')
	{
    
    
		std::cout << "a has pressed" << std::endl;
		struct callback_args* data = (struct callback_args *)args;
		if (*(data->isShow))
		{
    
    
			data->viewerPtr->removePointCloud("cloud");
			*(data->isShow) = false;
			std::cout << "remove" << std::endl;
		}
		else {
    
    
			data->viewerPtr->addPointCloud(data->orgin_points, "cloud");
			*(data->isShow) = true;
			std::cout << "add" << std::endl;
		}
	}
}

int main(int argc, char** argv)
{
    
    
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::io::loadPCDFile("bunny.pcd", *cloud);
	pcl::console::print_highlight("load cloud !\n");

	// 定义对象
	pcl::visualization::PCLVisualizer::Ptr viewer(new pcl::visualization::PCLVisualizer);
	viewer->addPointCloud(cloud, "cloud");

	// 初始化参数
	bool isShow = true;
	struct callback_args kb_args;
	kb_args.isShow = &isShow;
	kb_args.orgin_points = cloud;
	kb_args.viewerPtr = viewer;

	// 设置回掉函数
	viewer->registerKeyboardCallback(kb_callback, (void*)&kb_args);

	viewer->spin();

	return 0;
}

This code implements pressing a to clear the display, and then pressing it to redisplay.
Mainly set the callback function implementation

viewer->registerKeyboardCallback(kb_callback, (void*)&kb_args);

kb_callback implements specific functions.

click event

#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
#include <pcl/visualization/pcl_visualizer.h>

struct callback_args {
    
    
	// structure used to pass arguments to the callback function
	pcl::PointCloud<pcl::PointXYZ>::Ptr clicked_points_3d;
	pcl::visualization::PCLVisualizer::Ptr viewerPtr;
};

void pp_callback(const pcl::visualization::PointPickingEvent& event, void* args)
{
    
    
	struct callback_args* data = (struct callback_args *)args;

	if (event.getPointIndex() == -1)
		return;
	int index = event.getPointIndex();
	std::cout << "index: " << index << std::endl;
	pcl::PointXYZ current_point;
	event.getPoint(current_point.x, current_point.y, current_point.z);
	data->clicked_points_3d->points.push_back(current_point);
	// Draw clicked points in red:
	pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> red(data->clicked_points_3d, 255, 0, 0);
	data->viewerPtr->removePointCloud("clicked_points");
	data->viewerPtr->addPointCloud(data->clicked_points_3d, red, "clicked_points");
	data->viewerPtr->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 10, "clicked_points");
	std::cout << current_point.x << " " << current_point.y << " " << current_point.z << std::endl;
}

int main(int argc, char** argv)
{
    
    
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::io::loadPCDFile("bunny.pcd", *cloud);
	pcl::console::print_highlight("load cloud !\n");

	pcl::visualization::PCLVisualizer viewer;

	pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> green(cloud, 0, 255, 0);
	viewer.addPointCloud(cloud, green, "cloud");

	// Add point picking callback to viewer:
	struct callback_args cb_args;
	pcl::PointCloud<pcl::PointXYZ>::Ptr clicked_points_3d(new pcl::PointCloud<pcl::PointXYZ>);
	cb_args.clicked_points_3d = clicked_points_3d;
	cb_args.viewerPtr = pcl::visualization::PCLVisualizer::Ptr(&viewer);
	viewer.registerPointPickingCallback(pp_callback, (void*)&cb_args);
	pcl::console::print_highlight("Shift+click on three floor points, then press 'Q'...\n");

	// Spin until 'Q' is pressed:
	viewer.spin();

	system("pause");
	return 0;
}

renderings

Pressing shfit and clicking on a point prints the coordinates.

region selection event

#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
#include <pcl/visualization/pcl_visualizer.h>

struct callback_args{
    
    
	// structure used to pass arguments to the callback function
	pcl::PointCloud<pcl::PointXYZ>::Ptr orgin_points;
	pcl::PointCloud<pcl::PointXYZ>::Ptr chosed_points_3d;
	pcl::visualization::PCLVisualizer::Ptr viewerPtr;
};

void ap_callback(const pcl::visualization::AreaPickingEvent& event, void* args)
{
    
    
	struct callback_args* data = (struct callback_args *)args;
	std::vector<int> indiecs;

	if (!event.getPointsIndices(indiecs))
		return;
	for (int i = 0; i < indiecs.size(); ++i)
	{
    
    
		data->chosed_points_3d->push_back(data->orgin_points->points[indiecs[i]]);
	}
	
	// Draw clicked points in red:
	pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> red(data->chosed_points_3d, 255, 0, 0);
	data->viewerPtr->removePointCloud("chosed_points");
	data->viewerPtr->addPointCloud(data->chosed_points_3d, red, "chosed_points");
	data->viewerPtr->setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 5, "chosed_points");
	std::cout << "selected " << indiecs.size() << " points , now sum is " << data->chosed_points_3d->size() << std::endl;
}

int main(int argc, char** argv)
{
    
    
	pcl::PointCloud<pcl::PointXYZ>::Ptr cloud(new pcl::PointCloud<pcl::PointXYZ>);
	pcl::io::loadPCDFile("rabbit.pcd", *cloud);
	pcl::console::print_highlight("load cloud !\n");

	pcl::visualization::PCLVisualizer viewer;

	pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> green(cloud, 0, 255, 0);
	viewer.addPointCloud(cloud, green, "cloud");

	// Add point picking callback to viewer:
	struct callback_args cb_args;
	cb_args.orgin_points = cloud;
	pcl::PointCloud<pcl::PointXYZ>::Ptr chosed_points_3d(new pcl::PointCloud<pcl::PointXYZ>);
	cb_args.chosed_points_3d = chosed_points_3d;
	cb_args.viewerPtr = pcl::visualization::PCLVisualizer::Ptr(&viewer);
	viewer.registerAreaPickingCallback(ap_callback, (void*)&cb_args);
	pcl::console::print_highlight("press x enter slected model, then press 'qQ'...\n");

	// Spin until 'Q' is pressed:
	viewer.spin();

	system("pause");
	return 0;
}

Display area segmentation

pcl can divide the display area, from (xmin, ymin) to (xmax, ymax) a rectangular area, the range is (0, 1). Bottom left (0,0), top right (1,1). All previous functions support area display.

#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
// 包含相关头文件
#include <pcl/visualization/pcl_visualizer.h>

typedef pcl::PointXYZ PointT;

int main()
{
    
    
	// 读取点云
	pcl::PointCloud<PointT>::Ptr cloud(new pcl::PointCloud<PointT>);
	pcl::io::loadPCDFile("read.pcd", *cloud);

	// 定义对象
	pcl::visualization::PCLVisualizer viewer; 

	int v1(1); // viewport
	viewer.createViewPort(0.0, 0.0, 0.5, 1.0, v1);
	viewer.setBackgroundColor(255, 0, 0, v1);
	viewer.addPointCloud(cloud, "cloud1", v1);;

	int v2(2);// viewport
	viewer.createViewPort(0.5, 0.0, 1.0, 1.0, v1);
	viewer.setBackgroundColor(0, 255, 0, v2);
	viewer.addPointCloud(cloud, "cloud2", v2);;

	viewer.spin();

	system("pause");
	return 0;
}

Class 2: pcl::visualization::CloudViewer

#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>
// 包含相关头文件
#include <pcl/visualization/cloud_viewer.h>

typedef pcl::PointXYZ PointT;

int main()
{
    
    
	// 读取点云
	pcl::PointCloud<PointT>::Ptr cloud(new pcl::PointCloud<PointT>);
	pcl::io::loadPCDFile("read.pcd", *cloud);

	pcl::visualization::CloudViewer viewer("simple cloud viewer");
	viewer.showCloud(cloud);
	while (!viewer.wasStopped())
	{
    
    
		// todo::
	}

	system("pause");
	return 0;
}