PCL_tutorial, how to show the point cloud

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Hello,

I am following the tutorial of PCL with ROS (www.ros.org/wiki/pcl/Tutorials).

When i launch the openni i can see the topic is publishing. But when i try to use it to see the result, nothing happen (only black screen is showed in the rviz window).

What i have to do to show the result?

here is the code i use:

#include <ros/ros.h>
// PCL specific includes
#include <pcl/ros/conversions.h>
#include <pcl/point_cloud.h>
#include <pcl/point_types.h>

#include <pcl/filters/voxel_grid.h>

ros::Publisher pub;

void cloud_cb (const sensor_msgs::PointCloud2ConstPtr& cloud){
sensor_msgs::PointCloud2 cloud_filtered;

 // Perform the actual filtering
pcl::VoxelGrid<sensor_msgs::PointCloud2> sor;
sor.setInputCloud (cloud);
sor.setLeafSize (0.01, 0.01, 0.01);
sor.filter (cloud_filtered);

// Publish the data
pub.publish (cloud_filtered);
}

int main (int argc, char** argv){
// Initialize ROS
ros::init (argc, argv, "my_pcl_tutorial");
ros::NodeHandle nh;

 // Create a ROS subscriber for the input point cloud
ros::Subscriber sub = nh.subscribe ("input", 1, cloud_cb);

// Create a ROS publisher for the output point cloud
pub = nh.advertise<sensor_msgs::PointCloud2> ("output", 1);

// Spin
ros::spin ();
}

Thanks

--Pierre