pcl之transform a point cloud
阿新 • • 發佈:2018-11-19
pcl之transform a point cloud
#include <iostream> #include <pcl/io/pcd_io.h> #include <pcl/io/ply_io.h> #include <pcl/point_cloud.h> #include <pcl/console/parse.h> #include <pcl/common/transforms.h> #include <pcl/visualization/pcl_visualizer.h> // This function displays the help void showHelp(char * program_name) { std::cout << std::endl; std::cout << "Usage: " << program_name << " cloud_filename.[pcd|ply]" << std::endl; std::cout << "-h: Show this help." << std::endl; } // This is the main function int main (int argc, char** argv) { // Show help if (pcl::console::find_switch (argc, argv, "-h") || pcl::console::find_switch (argc, argv, "--help")) { showHelp (argv[0]); return 0; } // Fetch point cloud filename in arguments | Works with PCD and PLY files std::vector<int> filenames; bool file_is_pcd = false; filenames = pcl::console::parse_file_extension_argument (argc, argv, ".ply"); if (filenames.size () != 1) { filenames = pcl::console::parse_file_extension_argument (argc, argv, ".pcd"); if (filenames.size () != 1) { showHelp (argv[0]); return -1; } else { file_is_pcd = true; } } // Load file | Works with PCD and PLY files pcl::PointCloud<pcl::PointXYZ>::Ptr source_cloud (new pcl::PointCloud<pcl::PointXYZ> ()); if (file_is_pcd) { if (pcl::io::loadPCDFile (argv[filenames[0]], *source_cloud) < 0) { std::cout << "Error loading point cloud " << argv[filenames[0]] << std::endl << std::endl; showHelp (argv[0]); return -1; } } else { if (pcl::io::loadPLYFile (argv[filenames[0]], *source_cloud) < 0) { std::cout << "Error loading point cloud " << argv[filenames[0]] << std::endl << std::endl; showHelp (argv[0]); return -1; } } /* Reminder: how transformation matrices work : |-------> This column is the translation | 1 0 0 x | \ | 0 1 0 y | }-> The identity 3x3 matrix (no rotation) on the left | 0 0 1 z | / | 0 0 0 1 | -> We do not use this line (and it has to stay 0,0,0,1) METHOD #1: Using a Matrix4f This is the "manual" method, perfect to understand but error prone ! */ Eigen::Matrix4f transform_1 = Eigen::Matrix4f::Identity(); // Define a rotation matrix (see https://en.wikipedia.org/wiki/Rotation_matrix) float theta = M_PI/4; // The angle of rotation in radians transform_1 (0,0) = cos (theta); transform_1 (0,1) = -sin(theta); transform_1 (1,0) = sin (theta); transform_1 (1,1) = cos (theta); // (row, column) // Define a translation of 2.5 meters on the x axis. transform_1 (0,3) = 2.5; // Print the transformation printf ("Method #1: using a Matrix4f\n"); std::cout << transform_1 << std::endl; /* METHOD #2: Using a Affine3f This method is easier and less error prone */ Eigen::Affine3f transform_2 = Eigen::Affine3f::Identity(); // Define a translation of 2.5 meters on the x axis. transform_2.translation() << 2.5, 0.0, 0.0; // The same rotation matrix as before; theta radians around Z axis transform_2.rotate (Eigen::AngleAxisf (theta, Eigen::Vector3f::UnitZ())); // Print the transformation printf ("\nMethod #2: using an Affine3f\n"); std::cout << transform_2.matrix() << std::endl; // Executing the transformation pcl::PointCloud<pcl::PointXYZ>::Ptr transformed_cloud (new pcl::PointCloud<pcl::PointXYZ> ()); // You can either apply transform_1 or transform_2; they are the same pcl::transformPointCloud (*source_cloud, *transformed_cloud, transform_2); // Visualization printf( "\nPoint cloud colors : white = original point cloud\n" " red = transformed point cloud\n"); pcl::visualization::PCLVisualizer viewer ("Matrix transformation example"); // Define R,G,B colors for the point cloud pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> source_cloud_color_handler (source_cloud, 255, 255, 255); // We add the point cloud to the viewer and pass the color handler viewer.addPointCloud (source_cloud, source_cloud_color_handler, "original_cloud"); pcl::visualization::PointCloudColorHandlerCustom<pcl::PointXYZ> transformed_cloud_color_handler (transformed_cloud, 230, 20, 20); // Red viewer.addPointCloud (transformed_cloud, transformed_cloud_color_handler, "transformed_cloud"); viewer.addCoordinateSystem (1.0, "cloud", 0); viewer.setBackgroundColor(0.05, 0.05, 0.05, 0); // Setting background to a dark grey viewer.setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 2, "original_cloud"); viewer.setPointCloudRenderingProperties (pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 2, "transformed_cloud"); //viewer.setPosition(800, 400); // Setting visualiser window position while (!viewer.wasStopped ()) { // Display the visualiser until 'q' key is pressed viewer.spinOnce (); } return 0; }
What if you want to transform a single point ? A vector ?
We need a vector with 4 components. What do you put in the last component ? It depends on what you want to do:
- If you want to transform a point: put 1 at the end of the vector so that the translation is taken in account.
- If you want to transform the direction of a vector: put 0 at the end of the vector to ignore the translation.
Here’s a quick example, we want to transform the following vector:
[10, 5, 0, 3, 0, -1]
Where the first 3 components defines the origin coordinates and the last 3 components the direction.
This vector starts at point 10, 5, 0 and ends at 13, 5, -1.
This is what you need to do to transform the vector:
[10, 5, 0, 1] * 4x4_transformation_matrix [3, 0, -1, 0] * 4x4_transformation_matrix