Grab Pointclouds and save as pcd files using ROS and Openni

1) Install ROS Hydro Openni2 packages:

$sudo apt-get install ros-hydro-openni2-camera ros-hydro-openni2-launch

2) Run ROS

$roscore

3) Launch openni

$roslaunch openni2_launch openni2.launch

4) Launch RViz

$rosrun rviz rviz

5) Do settings in RViz to receive data from Kinect

6) Back in terminal, use the following command to save the point clouds

$rosrun pcl_ros pointcloud_to_pcd input:=<your target topic name>

For ex:

$ rosrun pcl_ros pointcloud_to_pcd input:=/camera/depth_registered/points

The output is :

[ INFO] [1412698428.630599815]: Listening for incoming data on topic /camera/depth_registered/points
[ INFO] [1412698428.870419685]: Received 307200 data points in frame /camera_rgb_optical_frame with the following fields: x y z rgb
[ INFO] [1412698428.870483694]: Data saved to 1412698428747359.pcd
[ INFO] [1412698429.421970793]: Received 307200 data points in frame /camera_rgb_optical_frame with the following fields: x y z rgb
[ INFO] [1412698429.422065179]: Data saved to 1412698429281241.pcd
[ INFO] [1412698429.979569838]: Received 307200 data points in frame /camera_rgb_optical_frame with the following fields: x y z rgb
[ INFO] [1412698429.979637397]: Data saved to 1412698429848510.pcd
[ INFO] [1412698430.495591052]: Received 307200 data points in frame /camera_rgb_optical_frame with the following fields: x y z rgb
[ INFO] [1412698430.495632948]: Data saved to 1412698430415787.pcd
[ INFO] [1412698430.974854796]: Received 307200 data points in frame /camera_rgb_optical_frame with the following fields: x y z rgb
[ INFO] [1412698430.974940083]: Data saved to 1412698430882933.pcd
 

(Ref: http://answers.ros.org/question/47345/kinect-point-cloud-to-pcd-files/ )
This will keep dumping the pointcloud files until you stop the process (ctrl + c).

Quick PCL commands to capture data using Kinect

$ pcl_openni_viewer
 press 'r' to visualize the point cloud. Pointcloud appears inverted manner. have to use mouse to see in correct orientation.

you can see 2 windows (PCL OpenNI cloud, PCL OpenNI Image)

$ pcl_openni_save_image  (saves depth and RGB image in .tiff format... You have to stop it if you want to save only 1 frame.)


View the depth image in octave:

$octave
octave:1> imshow('1_1_depth.tiff' , [])

$ pcl_openni_grabber_example
Warning: USB events thread - failed to set priority. This might cause loss of data...
<Esc>, 'q', 'Q': quit the program
' ': pause
's': save


$ pcl_viewer pcd_file.pcd
(press r to view, 5 to see color)

PCL: pointcloud transformation

// transform the model by the transformation value
  Eigen::Matrix4f txform;
 
 //get the txformation matrix (discussed below)

 pcl::transformPointCloud (*cloud_3dmodel, *txformed_model, txform );


ICP can be used to estimate the transform :

Eigen::Matrix4f txform;

 pcl::IterativeClosestPoint<pcl::PointXYZRGB, pcl::PointXYZRGB> icp;
 icp.setInputCloud(cloud_3dmodel);
 icp.setInputTarget(cloud_cluster);
 pcl::PointCloud<pcl::PointXYZRGB> Final;
 icp.align(Final);
 std::cout << "ICP has converged:" << icp.hasConverged() << " score: " <<    icp.getFitnessScore() << std::endl;
txform = icp.getFinalTransformation();

Refer:
http://stc0.wordpress.com/2013/03/22/equivalent-ways-to-register-two-point-clouds-with-pcl/
http://pointclouds.org/documentation/tutorials/iterative_closest_point.php 
http://robotica.unileon.es/mediawiki/index.php/PCL/OpenNI_tutorial_3:_Cloud_processing_%28advanced%29

Eigen: block access to matrices

  
 Eigen library: matrix block operation: 

 http://eigen.tuxfamily.org/dox-devel/group__TutorialBlockOperations.html


 //Code snippet to define a 4x4 transformation matrix:


  Eigen::Matrix4f txform;

  .........

  // Get Rotation Matrix and translation vector: T = [R | t]
  Eigen::Matrix3f rotation = txform.block<3,3>(0, 0);
  Eigen::Vector3f translation = txform.block<3,1>(0, 3);
 
  //Print he individual values
    printf ("\n");
    printf ("            | %6.3f %6.3f %6.3f | \n", rotation (0,0), rotation (0,1), rotation (0,2));
    printf ("        R = | %6.3f %6.3f %6.3f | \n", rotation (1,0), rotation (1,1), rotation (1,2));
    printf ("            | %6.3f %6.3f %6.3f | \n", rotation (2,0), rotation (2,1), rotation (2,2));
    printf ("\n");
    printf ("        t = < %0.3f, %0.3f, %0.3f >\n", translation (0), translation (1), translation (2));

   

A quick python tutorial

Here is the link to a quick python tutorial for beginners:

http://www.ccs.neu.edu/home/rplatt/cs5100_2014/pa0/hw_asst0.html

Hope it helps for people who want to begin with their work in python!

How to write Unicode text using LaTeX

Here is a ppt I made with my lab-mate Praveen Krishnan, where I have compiled how to write in LaTeX documents using different languages. I have compiled it from various sources ... I hope it is useful to you all...

http://researchweb.iiit.ac.in/~swagatika.panda/Documents/UnicodeText_Latex_Tutorial.pdf
 
References:

• Using Devanagari in Latex, http://pravin.paratey.com/posts/using-devanagari-in-latex , Accessed on:21stMarch,2014

• Devanagari for TEXVersion 1.2, User Manual

• Installing and using XeTeX http://tex.stackexchange.com/questions/35360/installing-and-using-xetex ,Accessed on: 22nd March, 2014

Split a PDF to many PDFs

Here is the link to Linux Commando's blogpost on using pdftk  to split a pdf.

http://linuxcommando.blogspot.in/2013/02/splitting-up-is-easy-for-pdf-file.html