G P I V Home Page

What is Gpiv?

Gpiv is a graphic user interface program for recording and analyzing images obtained from a fluid flow that has been seeded with tracer particles by the so-called Particle Image Velocimetry technique (PIV). The program allows to have a quick overview of the parameter settings of all processes, easily changing them, executing the processes and visualizing their results in an interactive way (Figure 1). Gpiv has been built with the Gtk/Gnome libraries and includes many interesting features.

screenshot Gpiv
Figure 1 Screenshot of Gpiv with PIV estimators (vectors) from an artificial, computer generated, image pair [1] and the derived vorticity field (background color)

Unpacking and compilation

You can download the Gpiv package here. For this package you will need:

libgpiv
libgtk and related packages.
libgnome and related packages.

Generally, unpacking, compilation and installation is quite straightforward with:

gzip -d gpiv-0.2.tar.gz
tar -xvf gpiv-0.2.tar
./configure
make (to build the library and tools)
make install
make uninstall (removes installed files and directories that have been created)

There are also pre-compiled (.deb) packages available that eases the installation.

Use of Gpiv

In order to understand how Gpiv works, just type the program name with -h option. There is a man page of Gpiv in the package and documentation, that can be displayed from the help menu or on-line . In case Gpiv will trigger a camera and lasers, it uses a kernel module gpivtrig_rtl from the gpivtrig package that depends on the Real Time Application Interface (RTAI) and RealtimeLinux. These modules will have to be loaded manually or Gpiv will have to be started with: "gpiv_control "gpiv key1 ..."". Gpiv_control has to be run with root privileges.

C.S.

There is also set of command-line driven programs with similar functionalities. These may be used for non-interactive purposes, used in scripts for batch processing etc. and can be found in the Gpiv-tools package. The core functions for processing, in-and output and utility functions are written in the Libgpiv library in order to share the resources of Gpiv and Gpiv-tools.

All software has been written in ANSI-C. It has been issued under the GNU General Public License and only uses libraries that are under this or other Open Source license. The objective of this project is to provide a maximum flexibility for extending and adapting the code by the main developer as well as by third parties, like its users. So it may be developed and applied for different applications with highest accuracies and spatial/time resolutions.
As with most of the open source projects, it is unfinished and its here to grow. Some ideas that might be worth to consider for extension are:

Improved solvers to obtain a higher accuracy and spatial resolution. Currently we are implementing image deformation techniques by means of B-spline interpolation.
Improved processing speed. A start has already been made by parallelization the interrogation tool gpiv_rr from the Gpiv-tools package with MPI.
Extension for stereoscopic (three-dimensional) PIV.
Extension with Particle Tracking Velocimetry (PTV) and, eventually, hybrid PIV-PTV for increasing spatial resolution.
Extension with data acquisition. This means connecting the software with (CCD) cameras and controlling electronics (sequencer) that triggers a light source (mostly a Nd-YAG laser) with the camera. A start has been made with this feature, as can be seen in the news.
Extension with other image analyzing techniques for fluid mechanics, like Light Induced Fluorescence (LIF) in order to obtain concentrations of chemical substances.
Keeping up to date with the libraries the Gpiv c.s. is a continuous source of work. Most important are the FFT and Graphic libraries. Gpiv is currently being ported to the Gtk/Gnome-2 libraries. The program works, but still needs a lot of adaptions.

Support

It is evident that the development and maintenance of such a project like this involves a large amount of work that cannot be performed by a single, voluntary, developer. Therefore, I would like to stress that support for this project is of fundamental importance. We are convinced that the continuity of it will definitely be advantageous for you as (aspirant) PIV user, developer and researcher. By issuing the software under the GNU General Public License it is intended as a community product that will be developed by its users, as well. The software is yours; you may freely use it and adapt it to your own needs, as long as the license conditions are respected. By sharing the experiences and knowledge as expressed in the software, everybody will profit of it; there may be a continuous increase in quality of the code due to peer review, less additional coding to implement new features, interrogation algorithms, porting to other Computer architectures and Operating Systems, etc. Just a thought. To mention a few suggestions for supporting the Gpiv c.s. projects:

Feedback: send comments, bug reports (and patches!), report if Gpiv c.s. does work, or not, on a different platform (as long as it is Unix-like), and with different cameras and lasers. Or, even better, report how it has been modified to make it work.
Participate in developing the software, the building system, translating the GUI to your language, maintaining web-pages.
Acknowledge the software project in reports and publications if it has considerably contributed to your research project and let me know it. If you'd like to, a reference will be given from here.
Let us be your partner: we are here to assist if you'd like to have support for Gpiv c.s.: extending the software for your needs, developing and installation of hard- and software, applying the technique for your research project.

News

Version 0.2.1

The software has been extended with Data Acquision (DAC), i.e. the triggering of lasers with a camera and the recording of PIV images from an experiment.
Adaptive grid if zero offsetting and adaptive dimensions of the Interrogation Area's (I.A) are used. The initial grid of an iterative interrogation uses the dimensions of the largest I.A.'s, as defined by the process parameter, while the area's have an overlap of 50 %. After each iteration sweep (which includes the interrogation of the entire Area of Interest within the image on a rectangular grid), the sizes and adjacent shifts of I.A.'s are halved. Estimators at the new, finer, grid are calculated by (bi)-linear interpolation. This process continues until the final (minimum) dimensions and shifts have been reached.

Sponser

The project is sponsered by the The Kramers Laboratorium voor Fysische Technologie at Delft University of Technology, the Netherlands.

Contact

I hope that Gpiv will work fine and that you'll enjoy it. If you would like to know more about PIV, wants to extend the code for your purposes or need some help, do not hesitate to drop me a line.

References

[1] Okamoto, K., Nishio, S., Saga, T. and Kobayashi, T., 2000, "Standard images for particle-image velocimetry," Meas. Sci. Technol., 11, 685-691. vsj.or.jp/piv/

Gerber van der Graaf
email: gerber_graaf AT users DOT sourceforge DOT net

Last modified: Wed Mar 14 09:54:22 CET 2007