一、什么是PCLVisualizer

  PCLVisualizer是PCL的全功能可视化类。虽然使用起来比CloudViewer更复杂，但它也更强大，提供了显示法线、绘制形状和多个视图等功能。

二、使用案例

  本节我们会使用历程展示PCLVisualizer的使用方法和一些特性，包括可视化单片点云，添加颜色，自定义颜色，显示法线和其他信息、多视窗显示等功能。
  请参考如下代码，注释非常清晰。

 /* 示例代码作者： Geoffrey Biggs */

 #include <iostream>
 #include <thread>
 
 #include <pcl/common/angles.h> // for pcl::deg2rad
 #include <pcl/features/normal_3d.h>
 #include <pcl/io/pcd_io.h>
 #include <pcl/visualization/pcl_visualizer.h>
 #include <pcl/console/parse.h>
 
 using namespace std::chrono_literals;
 
 // ---------------------
 // -----显示帮助信息-----
 // ---------------------
 void
 printUsage (const char* progName)
 {
   std::cout << "\n\nUsage: "<<progName<<" [options]\n\n"
             << "Options:\n"
             << "-------------------------------------------\n"
             << "-h           this help\n"
            << "-s           Simple visualisation example\n"
            << "-r           RGB colour visualisation example\n"
             << "-c           Custom colour visualisation example\n"
            << "-n           Normals visualisation example\n"
             << "-a           Shapes visualisation example\n"
             << "-v           Viewports example\n"
             << "-i           Interaction Customization example\n"
             << "\n\n";
 }
 
 
 pcl::visualization::PCLVisualizer::Ptr simpleVis (pcl::PointCloud<pcl::PointXYZ>::ConstPtr cloud)
 {
   // -------------------------------------------------
   // -----打开三维可视化工具PCLVisualizer并添加普通点云-----
   // -------------------------------------------------
   pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
   viewer->setBackgroundColor (0, 0, 0);// 设置背景颜色
   viewer->addPointCloud<pcl::PointXYZ> (cloud, "sample cloud");// 添加点云到窗口sample cloud
   viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 1, "sample cloud"); // 设置点云单点的尺寸
   viewer->addCoordinateSystem (1.0);// 添加坐标系
   viewer->initCameraParameters (); // 初始化相机参数
   return (viewer);
 }
 
 
 pcl::visualization::PCLVisualizer::Ptr rgbVis (pcl::PointCloud<pcl::PointXYZRGB>::ConstPtr cloud)
 {
   // -------------------------------------------------
   // -----打开三维可视化工具PCLVisualizer并添加RGB颜色点云-----
   // -------------------------------------------------
   pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
   viewer->setBackgroundColor (0, 0, 0);
   pcl::visualization::PointCloudColorHandlerRGBField<pcl::PointXYZRGB> rgb(cloud); // 创建RGB点云句柄，用于添加RGB点云
   viewer->addPointCloud<pcl::PointXYZRGB> (cloud, rgb, "sample cloud");
   viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud");
   viewer->addCoordinateSystem (1.0);
   viewer->initCameraParameters ();
   return (viewer);
 }
 
 
 pcl::visualization::PCLVisualizer::Ptr customColourVis (pcl::PointCloud<pcl::PointXYZ>::ConstPtr cloud)
 {
   // -----------------------------------------------
   // ----打开三维可视化工具PCLVisualizer并添加指定颜色点云----
   // -----------------------------------------------
   pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
   viewer->setBackgroundColor (0, 0, 0);
   pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> single_color(cloud, 0, 255, 0); // 设置指定颜色的点云(绿色)
   viewer->addPointCloud<pcl::PointXYZ> (cloud, single_color, "sample cloud");
   viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud");
   viewer->addCoordinateSystem (1.0);
   viewer->initCameraParameters ();
   return (viewer);
 }
 

 pcl::visualization::PCLVisualizer::Ptr normalsVis (
     pcl::PointCloud<pcl::PointXYZRGB>::ConstPtr cloud, pcl::PointCloud<pcl::Normal>::ConstPtr normals)
 {
   // --------------------------------------------------------
   // -----打开三维可视化工具PCLVisualizer并添加点云和法向-----
   // --------------------------------------------------------
   pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
   viewer->setBackgroundColor (0, 0, 0);
   pcl::visualization::PointCloudColorHandlerRGBField<pcl::PointXYZRGB> rgb(cloud);
   viewer->addPointCloud<pcl::PointXYZRGB> (cloud, rgb, "sample cloud");
   viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud");
   viewer->addPointCloudNormals<pcl::PointXYZRGB, pcl::Normal> (cloud, normals, 10, 0.05, "normals");// 显示法向，10表示只显示1/10的点的法向，0.05表示法向显示长度。
   viewer->addCoordinateSystem (1.0);
   viewer->initCameraParameters ();
   return (viewer);
 }
 
 
pcl::visualization::PCLVisualizer::Ptr shapesVis (pcl::PointCloud<pcl::PointXYZRGB>::ConstPtr cloud)
{
  // --------------------------------------------
  // -----打开三维可视化工具PCLVisualizer并添加点云-----
  // --------------------------------------------
  pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
106  viewer->setBackgroundColor (0, 0, 0);
107  pcl::visualization::PointCloudColorHandlerRGBField<pcl::PointXYZRGB> rgb(cloud);
108  viewer->addPointCloud<pcl::PointXYZRGB> (cloud, rgb, "sample cloud");
109  viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud");
  viewer->addCoordinateSystem (1.0);
  viewer->initCameraParameters ();

  //------------------------------------
  //-----Add 添加指定形状的点云-----
  //------------------------------------
  viewer->addLine<pcl::PointXYZRGB> ((*cloud)[0],
                                     (*cloud)[cloud->size() - 1], "line"); // 添加线状点云（点云的第一个点和最后一个点的连线）
  viewer->addSphere ((*cloud)[0], 0.2, 0.5, 0.5, 0.0, "sphere");
  // 添加球状点云，中心为第一个点位置，半径为0.5，后三个参数是颜色

  //---------------------------------------
  //-----在其他位置添加形状-----
  //---------------------------------------
  pcl::ModelCoefficients coeffs; // 添加模型的多项式系数
  coeffs.values.push_back (0.0);
  coeffs.values.push_back (0.0);
  coeffs.values.push_back (1.0);
  coeffs.values.push_back (0.0);
 	viewer->addPlane (coeffs, "plane"); // 4个系数ABCD可以确定一个平面
  coeffs.values.clear ();
  coeffs.values.push_back (0.3);
  coeffs.values.push_back (0.3);
  coeffs.values.push_back (0.0);
  coeffs.values.push_back (0.0);
  coeffs.values.push_back (1.0);
  coeffs.values.push_back (0.0);
  coeffs.values.push_back (5.0);
  viewer->addCone (coeffs, "cone"); // 7个系数ABCDEFG可以确定一个圆锥体

  return (viewer);
}


pcl::visualization::PCLVisualizer::Ptr viewportsVis (
    pcl::PointCloud<pcl::PointXYZRGB>::ConstPtr cloud, pcl::PointCloud<pcl::Normal>::ConstPtr normals1, pcl::PointCloud<pcl::Normal>::ConstPtr normals2)
{
  // --------------------------------------------------------
  // -----在同一窗口添加不同的点云和法向并列显示-----
  // --------------------------------------------------------
  pcl::visualization::PCLVisualizer::Ptr viewer (new 	   pcl::visualization::PCLVisualizer ("3D Viewer"));
 viewer->initCameraParameters ();

  int v1(0);
  viewer->createViewPort(0.0, 0.0, 0.5, 1.0, v1); // 添加视角V1，四个参数分别是X轴和Y轴的显示最大最小范围
  viewer->setBackgroundColor (0, 0, 0, v1);
  viewer->addText("Radius: 0.01", 10, 10, "v1 text", v1);
 pcl::visualization::PointCloudColorHandlerRGBField<pcl::PointXYZRGB> rgb(cloud);
  viewer->addPointCloud<pcl::PointXYZRGB> (cloud, rgb, "sample cloud1", v1);

  int v2(0);
  viewer->createViewPort(0.5, 0.0, 1.0, 1.0, v2);
  viewer->setBackgroundColor (0.3, 0.3, 0.3, v2);
  viewer->addText("Radius: 0.1", 10, 10, "v2 text", v2);
  pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZRGB> single_color(cloud, 0, 255, 0);
  viewer->addPointCloud<pcl::PointXYZRGB> (cloud, single_color, "sample cloud2", v2);

  viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud1");
167  viewer->setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 3, "sample cloud2");
  viewer->addCoordinateSystem (1.0);

  viewer->addPointCloudNormals<pcl::PointXYZRGB, pcl::Normal> (cloud, normals1, 10, 0.05, "normals1", v1);
  viewer->addPointCloudNormals<pcl::PointXYZRGB, pcl::Normal> (cloud, normals2, 10, 0.05, "normals2", v2);

  return (viewer);
}

// 以下是键盘输入响应
unsigned int text_id = 0;
void keyboardEventOccurred (const pcl::visualization::KeyboardEvent &event,
                            void* viewer_void)
{
  pcl::visualization::PCLVisualizer *viewer = static_cast<pcl::visualization::PCLVisualizer *> (viewer_void);
  if (event.getKeySym () == "r" && event.keyDown ())
  {
    std::cout << "r was pressed => removing all text" << std::endl;

    char str[512];
    for (unsigned int i = 0; i < text_id; ++i)
    {
      sprintf (str, "text#%03d", i);
      viewer->removeShape (str);
    }
    text_id = 0;
  }
}

// 鼠标事件响应
void mouseEventOccurred (const pcl::visualization::MouseEvent &event,
                         void* viewer_void)
{
  pcl::visualization::PCLVisualizer *viewer = static_cast<pcl::visualization::PCLVisualizer *> (viewer_void);
  if (event.getButton () == pcl::visualization::MouseEvent::LeftButton &&
      event.getType () == pcl::visualization::MouseEvent::MouseButtonRelease)
  {
   std::cout << "Left mouse button released at position (" << event.getX () << ", " << event.getY () << ")" << std::endl;

    char str[512];
    sprintf (str, "text#%03d", text_id ++);
   viewer->addText ("clicked here", event.getX (), event.getY (), str);
  }
}

pcl::visualization::PCLVisualizer::Ptr interactionCustomizationVis ()
{
  pcl::visualization::PCLVisualizer::Ptr viewer (new pcl::visualization::PCLVisualizer ("3D Viewer"));
  viewer->setBackgroundColor (0, 0, 0);
  viewer->addCoordinateSystem (1.0);
// 注册键盘和和鼠标响应回调函数
  viewer->registerKeyboardCallback (keyboardEventOccurred, (void*)viewer.get ());
  viewer->registerMouseCallback (mouseEventOccurred, (void*)viewer.get ());

  return (viewer);
}


// --------------
// -----Main-----
// --------------
int
main (int argc, char** argv)
{
  // --------------------------------------
  // -----命令行解析-----
  // --------------------------------------
  if (pcl::console::find_argument (argc, argv, "-h") >= 0)
  {
    printUsage (argv[0]);
    return 0;
  }
  bool simple(false), rgb(false), custom_c(false), normals(false),
    shapes(false), viewports(false), interaction_customization(false);
  if (pcl::console::find_argument (argc, argv, "-s") >= 0)
  {
    simple = true;
    std::cout << "Simple visualisation example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-c") >= 0)
  {
    custom_c = true;
   std::cout << "Custom colour visualisation example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-r") >= 0)
  {
    rgb = true;
    std::cout << "RGB colour visualisation example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-n") >= 0)
  {
    normals = true;
    std::cout << "Normals visualisation example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-a") >= 0)
  {
    shapes = true;
    std::cout << "Shapes visualisation example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-v") >= 0)
  {
    viewports = true;
    std::cout << "Viewports example\n";
  }
  else if (pcl::console::find_argument (argc, argv, "-i") >= 0)
  {
    interaction_customization = true;
    std::cout << "Interaction Customization example\n";
  }
  else
  {
    printUsage (argv[0]);
    return 0;
  }

  // ------------------------------------
  // -----创建示例点云-----
  // ------------------------------------
  pcl::PointCloud<pcl::PointXYZ>::Ptr basic_cloud_ptr (new pcl::PointCloud<pcl::PointXYZ>);
  pcl::PointCloud<pcl::PointXYZRGB>::Ptr point_cloud_ptr (new pcl::PointCloud<pcl::PointXYZRGB>);
  std::cout << "Generating example point clouds.\n\n";
 // 我们要做一个沿z轴挤压的椭圆。XYZRGB云的颜色将逐渐从红色到绿色再到蓝色。
  std::uint8_t r(255), g(15), b(15);
  for (float z(-1.0); z <= 1.0; z += 0.05)
  {
    for (float angle(0.0); angle <= 360.0; angle += 5.0)
    {
     pcl::PointXYZ basic_point;
      basic_point.x = 0.5 * std::cos (pcl::deg2rad(angle));
      basic_point.y = sinf (pcl::deg2rad(angle));
      basic_point.z = z;
      basic_cloud_ptr->points.push_back(basic_point);

      pcl::PointXYZRGB point;
      point.x = basic_point.x;
      point.y = basic_point.y;
      point.z = basic_point.z;
      point.r = r;
      point.g = g;
      point.b = b;
      point_cloud_ptr->points.push_back (point);
    }
    if (z < 0.0)
    {
      r -= 12;
      g += 12;
    }
    else
    {
      g -= 12;
      b += 12;
    }
  }
  basic_cloud_ptr->width = basic_cloud_ptr->size ();
  basic_cloud_ptr->height = 1;
  point_cloud_ptr->width = point_cloud_ptr->size ();
  point_cloud_ptr->height = 1;

  // ----------------------------------------------------------------
  // -----计算表面法向，搜索半径0.05-----
  // ----------------------------------------------------------------
  pcl::NormalEstimation<pcl::PointXYZRGB, pcl::Normal> ne;
  ne.setInputCloud (point_cloud_ptr);
  pcl::search::KdTree<pcl::PointXYZRGB>::Ptr tree (new pcl::search::KdTree<pcl::PointXYZRGB> ());
  ne.setSearchMethod (tree);
  pcl::PointCloud<pcl::Normal>::Ptr cloud_normals1 (new pcl::PointCloud<pcl::Normal>);
  ne.setRadiusSearch (0.05);
  ne.compute (*cloud_normals1);

  // ---------------------------------------------------------------
  // -----计算表面法向，搜索半径0.1-----
  // ---------------------------------------------------------------
  pcl::PointCloud<pcl::Normal>::Ptr cloud_normals2 (new pcl::PointCloud<pcl::Normal>);
  ne.setRadiusSearch (0.1);
  ne.compute (*cloud_normals2);

// 开始显示点云
  pcl::visualization::PCLVisualizer::Ptr viewer;
  if (simple)
  {
    viewer = simpleVis(basic_cloud_ptr);
  }
  else if (rgb)
  {
    viewer = rgbVis(point_cloud_ptr);
  }
  else if (custom_c)
  {
    viewer = customColourVis(basic_cloud_ptr);
  }
  else if (normals)
  {
      viewer = normalsVis(point_cloud_ptr, cloud_normals2);
  }
  else if (shapes)
  {
    viewer = shapesVis(point_cloud_ptr);
  }
  else if (viewports)
  {
    viewer = viewportsVis(point_cloud_ptr, cloud_normals1, cloud_normals2);
  }
  else if (interaction_customization)
  {
    viewer = interactionCustomizationVis();
  }

  //--------------------
  // -----Main loop-----
  //--------------------
  while (!viewer->wasStopped ())
 {
    viewer->spinOnce (100);
    std::this_thread::sleep_for(100ms);
  }
}
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以上操作的视图显示如下：
1.普通点云

2.RGB点云

3.单色点云

4.RGB点云带法向

5.RGB点云带法向，并创建线、圆锥和球点云

6. 一个视图内两片点云

7.鼠标响应和键盘响应

---

【博主简介】
  斯坦福的兔子，男，天津大学工学硕士。毕业至今从事光学三维成像及点云处理相关工作。因工作中使用的三维处理库为公司内部库，不具有普遍适用性，遂自学开源PCL库及其相关数学知识以备使用。谨此将自学过程与君共享。
博主才疏学浅，尚不具有指导能力，如有问题还请各位在评论处留言供大家共同讨论。