Using Point Cloud Library to store Point Clouds from Kinect - kinect

Question

Using Point Cloud Library on Ubuntu, I am trying to take multiple point clouds from the Kinect and store them in memory for later use in the program. My code shown at the bottom of this post is designed to store the first Point Cloud from the Kinect and output its width and height. The program gives me a runtime error:
/usr/include/boost/smart_ptr/shared_ptr.hpp:418: T* boost::shared_ptr<T>::operator->() const [with T = pcl::PointCloud<pcl::PointXYZ>]: Assertion `px != 0' failed.
All help is greatly appreciated and I always accept an answer!
The code:
#include <pcl/io/openni_grabber.h>
#include <pcl/visualization/cloud_viewer.h>
class SimpleOpenNIViewer
{
public:
SimpleOpenNIViewer () : viewer ("PCL OpenNI Viewer") {}
pcl::PointCloud<pcl::PointXYZ>::Ptr prevCloud;
void cloud_cb_ (const pcl::PointCloud<pcl::PointXYZ>::ConstPtr &cloud)
{
if (!viewer.wasStopped())
viewer.showCloud (cloud);
//ICP start
if(!prevCloud) {
pcl::PointCloud<pcl::PointXYZ>::Ptr prevCloud( new pcl::PointCloud<pcl::PointXYZ>());
pcl::copyPointCloud<pcl::PointXYZ, pcl::PointXYZ>(*cloud, *prevCloud);
}
cout << prevCloud->width << " by " << prevCloud->height << endl;
}
void run ()
{
pcl::Grabber* interface = new pcl::OpenNIGrabber();
boost::function<void (const pcl::PointCloud<pcl::PointXYZ>::ConstPtr&)> f =
boost::bind (&SimpleOpenNIViewer::cloud_cb_, this, _1);
interface->registerCallback (f);
interface->start ();
while (!viewer.wasStopped())
{
boost::this_thread::sleep (boost::posix_time::seconds (1));
}
interface->stop ();
}
pcl::visualization::CloudViewer viewer;
};
int main ()
{
SimpleOpenNIViewer v;
v.run ();
return 0;
}

Answer 1

Try this, I don't have the Kinect drivers installed so I can't test. Basically in my version prevCloud is instantiated in the constructor so (!prevCloud) will always equal 'false'. Which is to say prevCloud.get() != NULL.
#include <pcl/io/openni_grabber.h>
#include <pcl/visualization/cloud_viewer.h>
class SimpleOpenNIViewer
{
typedef pcl::PointXYZ Point;
typedef pcl::PointCloud<Point> PointCloud;
public:
SimpleOpenNIViewer () : viewer ("PCL OpenNI Viewer") {
prevCloud = PointCloud::Ptr(NULL);
}
void cloud_cb_ (const PointCloud::ConstPtr &cloud)
{
if (!viewer.wasStopped())
viewer.showCloud (cloud);
if (!prevCloud) // init previous cloud if first frame
prevCloud = PointCloud::Ptr(new PointCloud);
else. // else RunICP between cloud and prevCloud
//RunICP(cloud,prevCloud);
//Copy new frame in to prevCloud
pcl::copyPointCloud<Point, Point>(*cloud, *prevCloud);
cout << prevCloud->width << " by " << prevCloud->height << endl;
}
void run ()
{
pcl::Grabber* interface = new pcl::OpenNIGrabber();
boost::function<void (const PointCloud::ConstPtr&)> f =
boost::bind (&SimpleOpenNIViewer::cloud_cb_, this, _1);
interface->registerCallback (f);
interface->start ();
while (!viewer.wasStopped())
{
boost::this_thread::sleep (boost::posix_time::seconds (1));
}
interface->stop ();
}
PointCloud::Ptr prevCloud;
pcl::visualization::CloudViewer viewer;
};
int main ()
{
SimpleOpenNIViewer v;
v.run ();
return 0;
}

Answer 2

You're creating a new local variable prevCloud and copying cloud into it, rather than copying into the prevCloud field. So, if the field's value was null before the if {}, it is still null after the if {} and so it throws an error when you try to dereference it.

Answer 3

May be this code can help you, the cloud is saved in a "pcd" file, take a look here
And other option is work with the "Kinfu" project from PCL