PCL zoom out functionality - c++

Question

I am new to Point Cloud Library (PCL) and C++ programming. I load multiple .ply files given as the arguments (say test0.ply,test1.ply...test99.ply) and visualize them one after another as if they are frames of videos.
Below is what I've tried so far. How can I get farther from the model during each frame (zoom out) ? The setCameraPosition function looks related, but the description is confusing.
UPDATE: We need to find the camera's current_position and play with it. Just like zoom in/out.
#include <iostream>
//#include <unistd.h>
#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;
}
// 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 PLY files
std::vector<int> filenames;
filenames = pcl::console::parse_file_extension_argument(argc, argv, ".ply");
// Visualization
printf("\n Point cloud colors :\n"
" \t white \t = \t original point cloud \n");
pcl::visualization::PCLVisualizer viewer(" Point Cloud Visualizer");
viewer.setBackgroundColor(0.05, 0.05, 0.05, 0); // Set background to a dark grey
// Load file | Works with PLY files
pcl::PointCloud<pcl::PointXYZRGB>::Ptr source_cloud(new pcl::PointCloud<pcl::PointXYZRGB>());
int i = 0;
while (1)
{
// int v1(0);
// viewer.createViewPort(0.0, 0.0, 0.5, 1.0, v1);
i++;
cout << argv[filenames[i % 10]] << endl;
if (pcl::io::loadPLYFile(argv[filenames[i % 10]], *source_cloud) < 0)
{
std::cout << "Error loading point cloud " << argv[filenames[(i % 10) + 1]] << std::endl << std::endl;
showHelp(argv[(i % 10) + 1]);
return -1;
}
// Define R,G,B colors for the point cloud
pcl::visualization::PointCloudColorHandlerRGBField<pcl::PointXYZRGB> rgb(source_cloud);
// We add the point cloud to the viewer and pass the color handler
viewer.addPointCloud(source_cloud, rgb, "original_cloud" + i);
viewer.setPointCloudRenderingProperties(pcl::visualization::PCL_VISUALIZER_POINT_SIZE, 2, "original_cloud" + i);
viewer.spinOnce();
viewer.removePointCloud("original_cloud" + i);
}
return 0;
} // End main()

Answer 1

I think you are on the right track and setCameraPosition() should be what you are looking for. Here is some example code that focus the camera on a specific point and places the camera 5 meters away in the y dimension.
pcl::PointXYZI center = centerPoint(cloud);
viewer->setCameraPosition(center.x, center.y - 5, center.z, 0, 0, 1);
std::vector<pcl::visualization::Camera> cams;
viewer->getCameras(cams);
for (auto&& camera : cams)
{
camera.focal[0] = center.x;
camera.focal[1] = center.y;
camera.focal[2] = center.z;
}
viewer->setCameraParameters(cams[0]);