IO

Read PCD

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>

int main (int argc, char** argv)
{
  pcl::PointCloud<pcl::PointXYZ>::Ptr cloud (new pcl::PointCloud<pcl::PointXYZ>);

  if (pcl::io::loadPCDFile<pcl::PointXYZ> ("test_pcd.pcd", *cloud) == -1) //* load the file
  {
    PCL_ERROR ("Couldn't read file test_pcd.pcd \n");
    return (-1);
  }
  return (0);
}

Write PCD

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>

int main (int argc, char** argv)
{
  pcl::PointCloud<pcl::PointXYZ> cloud;

  // Fill in the cloud data
  cloud.width    = 5;
  cloud.height   = 1;
  cloud.is_dense = false;
  cloud.points.resize (cloud.width * cloud.height);

  for (size_t i = 0; i < cloud.points.size (); ++i)
  {
    cloud.points[i].x = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud.points[i].y = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud.points[i].z = 1024 * rand () / (RAND_MAX + 1.0f);
  }

  pcl::io::savePCDFileASCII ("test_pcd.pcd", cloud);
  return (0);
}

Concatenate PCD

#include <iostream>
#include <pcl/io/pcd_io.h>
#include <pcl/point_types.h>

int main (int argc, char** argv)
{
  if (argc != 2)
  {
    std::cerr << "please specify command line arg '-f' or '-p'" << std::endl;
    exit(0);
  }
  pcl::PointCloud<pcl::PointXYZ> cloud_a, cloud_b, cloud_c;
  pcl::PointCloud<pcl::Normal> n_cloud_b;
  pcl::PointCloud<pcl::PointNormal> p_n_cloud_c;

  // Fill in the cloud data
  cloud_a.width  = 5;
  cloud_a.height = cloud_b.height = n_cloud_b.height = 1;
    cloud_a.points.resize (cloud_a.width * cloud_a.height);
  if (strcmp(argv[1], "-p") == 0)
  {
    cloud_b.width  = 3;
    cloud_b.points.resize (cloud_b.width * cloud_b.height);
  }
  else{
    n_cloud_b.width = 5;
    n_cloud_b.points.resize (n_cloud_b.width * n_cloud_b.height);
  }

  for (size_t i = 0; i < cloud_a.points.size (); ++i)
  {
    cloud_a.points[i].x = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud_a.points[i].y = 1024 * rand () / (RAND_MAX + 1.0f);
    cloud_a.points[i].z = 1024 * rand () / (RAND_MAX + 1.0f);
  }
  if (strcmp(argv[1], "-p") == 0)
    for (size_t i = 0; i < cloud_b.points.size (); ++i)
    {
      cloud_b.points[i].x = 1024 * rand () / (RAND_MAX + 1.0f);
      cloud_b.points[i].y = 1024 * rand () / (RAND_MAX + 1.0f);
      cloud_b.points[i].z = 1024 * rand () / (RAND_MAX + 1.0f);
    }
  else
    for (size_t i = 0; i < n_cloud_b.points.size (); ++i)
    {
      n_cloud_b.points[i].normal[0] = 1024 * rand () / (RAND_MAX + 1.0f);
      n_cloud_b.points[i].normal[1] = 1024 * rand () / (RAND_MAX + 1.0f);
      n_cloud_b.points[i].normal[2] = 1024 * rand () / (RAND_MAX + 1.0f);
    }
  std::cerr << "Cloud A: " << std::endl;
  for (size_t i = 0; i < cloud_a.points.size (); ++i)
    std::cerr << "    " << cloud_a.points[i].x << " " << cloud_a.points[i].y << " " << cloud_a.points[i].z << std::endl;

  std::cerr << "Cloud B: " << std::endl;
  if (strcmp(argv[1], "-p") == 0)
    for (size_t i = 0; i < cloud_b.points.size (); ++i)
      std::cerr << "    " << cloud_b.points[i].x << " " << cloud_b.points[i].y << " " << cloud_b.points[i].z << std::endl;
  else
    for (size_t i = 0; i < n_cloud_b.points.size (); ++i)
      std::cerr << "    " << n_cloud_b.points[i].normal[0] << " " << n_cloud_b.points[i].normal[1] << " " << n_cloud_b.points[i].normal[2] << std::endl;

  // Copy the point cloud data
  if (strcmp(argv[1], "-p") == 0)
  {
    cloud_c  = cloud_a;
    cloud_c += cloud_b;
    std::cerr << "Cloud C: " << std::endl;
    for (size_t i = 0; i < cloud_c.points.size (); ++i)
      std::cerr << "    " << cloud_c.points[i].x << " " << cloud_c.points[i].y << " " << cloud_c.points[i].z << " " << std::endl;
  }
  else
  {
    pcl::concatenateFields (cloud_a, n_cloud_b, p_n_cloud_c);
    std::cerr << "Cloud C: " << std::endl;
    for (size_t i = 0; i < p_n_cloud_c.points.size (); ++i)
      std::cerr << "    " <<
        p_n_cloud_c.points[i].x << " " << p_n_cloud_c.points[i].y << " " << p_n_cloud_c.points[i].z << " " <<
        p_n_cloud_c.points[i].normal[0] << " " << p_n_cloud_c.points[i].normal[1] << " " << p_n_cloud_c.points[i].normal[2] << std::endl;
  }
  return (0);
}

Read, write PCD

#include <pcl/io/pcd_io.h>
pcl::PointClound<pcl::PointXYZ>::Ptr cloud(new pcl::PointClound<pcl::PointXYZ>);

//Read
pcl::io::loadPCDFile<pcl::PointXYZ>("sample_pcd.pcd", *cloud);

if (pcl::io::loadPCDFile<pcl::PointXYZ> (argv[1], *cloud) == -1) //* load the file
  {
    PCL_ERROR ("Couldn't read file test_pcd.pcd \n");
    return (-1);
  }

//Write
pcl::io::savePCDFileASCII("output.pcd", *cloud);
pcl::io::savePCDFileBinary("output.pcd", *cloud);

//Visualization
pcl::visualization::CloudViewer viewer("viewer1");
viewer.showCloud(cloud);
while (!viewer.wasStopped())
{
  //do nothing but wait
}

//Concatenate clouds (the same type of point clound)
*cloud_C = (*cloud_A) + (*cloud_B);



//Matrix transform
pcl::PointCloud<pcl::PointXYZ>::Ptr transformed(new pcl::PointCloud<pcl::PointXYZ>);

Eigen::Matrix4f transformation = Eigen::Matrix4f::Identity();

//set a rotation around the Z axis
float theata = M_PI/2; // 180 degree (in radius)
transformation(0, 0) = cos(theta);
transformation(0, 1) = -sin(theta);
transformation(1, 0) = sin(theta);
transformation(1, 1) = cos(theta);  

//set a translation on the axis
transformation(0, 3) = 1.0f;  //1 meter (positive direction)

pcl::transformPointCloud(*cloud, *transformed, transformation);

pcl::visualization::PCLVisualizer viewer("viewer1");
viewer.addPointCloud(cloud, "original");
pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> colorHandler(transformed, 255, 255, 255);
viewer.addPointCloud(transformed, "transformed");
viewer.addCoordinateSystem(1.0, "reference",0);

while (!viewer.wasStopped())
{
  viewer.spinOnce();
}