marker array not visible in rviz but is getting published..

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I am trying display marker array in rviz. The marker is published succesfully but is not visible in rviz. The code is below:

int
main (int argc, char** argv)
{

visualization_msgs::Marker marker;
visualization_msgs::MarkerArray marker_array_msg;

  // Initialize ROS
  ros::init (argc, argv, "pcl_tabletop");
  ros::NodeHandle nh;

  pub_marker = nh.advertise<visualization_msgs::MarkerArray>("normals_marker_array", 100);
//pub_marker1 = nh.advertise<visualization_msgs::Marker>("normals_marker", 0);
/*while(1)
{

marker.header.frame_id = "base_link";
marker.header.stamp = ros::Time();
marker.ns = "my_namespace";
marker.id = 120;
marker.type = visualization_msgs::Marker::SPHERE;
marker.action = visualization_msgs::Marker::ADD;
marker.pose.position.x = 1;
marker.pose.position.y = 1;
marker.pose.position.z = 1;
marker.pose.orientation.x = 0.0;
marker.pose.orientation.y = 0.0;
marker.pose.orientation.z = 0.0;
marker.pose.orientation.w = 1.0;
marker.scale.x = 1;
marker.scale.y = 0.1;
marker.scale.z = 0.1;
marker.color.a = 1.0;
marker.color.r = 1.0;
marker.color.g = 0.0;
marker.color.b = 0.0;

//pub_marker.publish(marker_array_msg);

pub_marker1.publish(marker);
}*/

marker_array_msg.markers.resize(5);//final->width * final->height);
for ( int i = 0; i < 5; i++)
{
    marker_array_msg.markers[i].header.frame_id = "base_link";
    marker_array_msg.markers[i].header.stamp = ros::Time();
    marker_array_msg.markers[i].ns = "my_namespace";
    marker_array_msg.markers[i].id = i;
    marker_array_msg.markers[i].type = visualization_msgs::Marker::SPHERE;
    marker_array_msg.markers[i].action = visualization_msgs::Marker::ADD;
    marker_array_msg.markers[i].pose.position.x = i+50;
    marker_array_msg.markers[i].pose.position.y = 50+i;
    marker_array_msg.markers[i].pose.position.z = 10+i;
    marker_array_msg.markers[i].pose.orientation.x = 0.0;
    marker_array_msg.markers[i].pose.orientation.y = 0.0;
    marker_array_msg.markers[i].pose.orientation.z = 0.0;
    marker_array_msg.markers[i].pose.orientation.w = 1.0;
    marker_array_msg.markers[i].scale.x = 1;
    marker_array_msg.markers[i].scale.y = 0.1;
    marker_array_msg.markers[i].scale.z = 0.1;
    marker_array_msg.markers[i].color.a = 1.0;
    marker_array_msg.markers[i].color.r = 0.0;
    if (i == 0)
    {
        marker_array_msg.markers[i].color.g = 0.1;
    }
    else
    {
        marker_array_msg.markers[i].color.g = i * 0.15;
    }
    marker_array_msg.markers[i].color.b = 0.0;

     //marker_array_msg.markers.push_back(mark);
}
while(1)
{
 pub_marker.publish(marker_array_msg);
}

  // Spin
  ros::spin ();
}

I tried both Marker and MarkerArray types but its not visible in rviz. Am i doing something wrong when assigning values to marker array ?? This was my first try with marker array further actually i want to display segmented pcl data as marker array.

Any idea what is wrong please :)