（九）Filtering 体素下采样

点云样例：
https://raw.github.com/PointCloudLibrary/data/master/tutorials/table_scene_lms400.pcd

以下程序实现对读取的点云进行体素下采样，并将得到的点云保存。

voxel_grid.cpp

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

int main ()
{
  pcl::PCLPointCloud2::Ptr cloud (new pcl::PCLPointCloud2 ());
  pcl::PCLPointCloud2::Ptr cloud_filtered (new pcl::PCLPointCloud2 ());

  // 读取点云数据
  pcl::PCDReader reader;
  reader.read ("table_scene_lms400.pcd", *cloud); 

  std::cerr << "PointCloud before filtering: " << cloud->width * cloud->height 
       << " data points (" << pcl::getFieldsList (*cloud) << ")." << std::endl;

  // 使用体素大小为1cm的体素下采样滤波器进行滤波
  pcl::VoxelGrid<pcl::PCLPointCloud2> sor;
  sor.setInputCloud (cloud);
  sor.setLeafSize (0.01f, 0.01f, 0.01f);  
  sor.filter (*cloud_filtered);

  std::cerr << "PointCloud after filtering: " << cloud_filtered->width * cloud_filtered->height 
       << " data points (" << pcl::getFieldsList (*cloud_filtered) << ")." << std::endl;
  // 保存下采样的点云
  pcl::PCDWriter writer;
  writer.write ("table_scene_lms400_downsampled.pcd", *cloud_filtered, 
         Eigen::Vector4f::Zero (), Eigen::Quaternionf::Identity (), false);

  return (0);
}

CMakeLists.txt

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)
project(voxel_grid)
find_package(PCL 1.2 REQUIRED)

include_directories(${PCL_INCLUDE_DIRS})
link_directories(${PCL_LIBRARY_DIRS})
add_definitions(${PCL_DEFINITIONS})

add_executable (voxel_grid voxel_grid.cpp)
target_link_libraries (voxel_grid ${PCL_LIBRARIES})

编译并运行：

./voxel_grid

PointCloud before filtering: 460400 data points (x y z intensity distance sid).
PointCloud after filtering: 41049 data points (x y z intensity distance sid).

原始点云（460400 个点）：

下采样后的点云（41049 个点）：