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reacTIVision 1.4 ---------------(c) 2005-2009 by Martin Kaltenbrunner <[email protected]> http://reactivision.sourceforge.net/ reacTIVision is an open source, cross-platform computer vision framework for the fast and robust tracking of fiducial markers attached onto physical objects, as well as for multi-touch finger tracking. It was mainly designed as a toolkit for the rapid development of table-based tangible user interfaces (TUI) and multi-touch interactive surfaces. This framework has been developed by Martin Kaltenbrunner and Ross Bencina at the Music Technology Group at the Universitat Pompeu Fabra in Barcelona, Spain as part of the the reacTable project, a novel electronic music instrument with a table-top multi-touch tangible user interface. reacTIVision is a standalone application, which sends OpenSound Control messages via a UDP network socket to any connected client application. It implements the TUIO protocol, which was specially designed for transmitting the state of tangible objects and multi-touch events on a table surface. As an alternative reacTIVision can also send MIDI messages. The framework includes a set of example client projects for various programming languages, which serve as a base for the easy development of tangible user interface or multi-touch applications. Example projects are available for languages such as: C/C++, Java, C#, Processing, Pure Data, Max/MSP, Flash and Quartz Composer. The reacTIVision application runs and compiles under the following operating systems: Windows, Mac OS X and Linux Under Windows it suports any camera with a proper WDM driver, such as USB, USB2, FireWire and DV cameras. Under Mac OS X all FireWire cameras and any camera supported by QuickTime will work in reacTIVision. Under Linux FireWire cameras are best supported as well many V4L2 USB and USB2 cameras. Fiducial Symbols ---------------This application was designed to track specially designed fiducial markers. You will find the default "amoeba" set of 216 fiducials within the document "default.pdf" within the symbols folder. Print this document and attach the labels to any object you want to track. The default fiducial tracking engine is using Ross Bencina's fidtrack library which is basically a newer high-performance implementation of Enrico Costanza's d-touch concept. Alternatively you can use the "classic" or the original "dtouch" sets. See below how to configure the application to use these older symbol sets. reacTIVision detects the ID, position and rotation angle of fiducial markers in the video image and transmits these values to the client application via TUIO, a protocol based on Open Sound Control. TUIO assigns a session ID to each object in the scene and transmits this session ID along with the fiducial ID. This allows the identification and tracking of several objects with the same ID. Finger Tracking ---------------

reacTIVision also allows multi-touch finger tracking, which is basically interpreting any round white region of a given size as a finger that is touching the surface. Finger tracking is turned off by default and can be enabled by pressing the 'F' key and adjusting the average finger size, which is given in pixels. The general recognition sensitivity can also be adjusted, where the value is given as a percentage. 80 would be less sensitive and 120 more sensitive, which means that also less probable regions are interpreted as a finger. The finger tracking should work with DI (diffuse illumination) as well as with FTIR solutions. Application Handling -------------------Before starting the reacTIVision application make sure you have a supported camera connected to your system. The application will obviously not work at all without a camera. When running the application will show a single video window with the current camera image in B&W. Pressing the 'S' key will show to the original source image. Pressing 'T' will show the binary tresholded image, pressing the 'N' key will turn the display off, which reduces the CPU usage. The thresholder gradient gate can be adjusted by hitting the 'G' key. Lowering the value can improve the thresholder performance in low light conditions with insufficient finger contrast for example. You can gradually lower the value just before noise appears in the image. The camera options can be adjusted by pressing the 'O' key. On Windows and Mac OS this will show a system dialog that allows the adjustment of the available camera parameters. On Linux (Mac OS X when using IEEE1394 cameras), the available camera settings can be adjusted with a simple on screen display. In order to produce some more verbose debugging output, hitting the 'V' will print the symbol and finger data to the console. Pressing the 'H' key will display all these options on the screen. The 'P' key pauses the image analysis completely, hitting 'ESC' will quit the application. XML configuration file ---------------------Common settings can be edited within the file "reacTIVision.xml" where all changes are stored automatically when closing the application. Under Mac OS X the XML configuration file can be found within the application bundle's Resources folder. Select "Show Package Contents" from the application's context menu in order to access and edit the file. The reacTIVision application usually sends the TUIO messages to port 3333 on locahost (127.0.0.1) You can change this setting by adding or editing the XML tag to the configuration. The XML tag lets you select the fiducial engine or an alternative amoeba tree order. The default engine is using the fastest and effective 'amoeba' fiducial set. Add the 'classic' option in order to use Ross'

initial d-touch reimplementation. You can select Enrico's original d-touch engine by providing the 'dtouch' option. The display attribute defines the default screen upon startup. The lets you adjust the default gradient gate value. reacTIVision comes with a background subtraction module, which in some cases can increase the recognition performance of both the finger and fiducial tracking. Within the running application you can toggle this with the 'E' key or recalculate the background subtraction by hitting the SPACE bar. The overall camera settings can be configured within the camera.xml configuration file. Please note that for Windows and the Quicktime mode on Mac OS X this only allows the configuration of the image size. For IEEE1394 cameras on Mac OS X as well as all camera types on Linux all image parameters can be fully configured using configuration file. TUIO vs. MIDI ------------The application can alternatively send MIDI messages, which allows to map any object dimension (xpos, ypos, angle) to a MIDI control with an XML configuration file. Adding and removing objects can be mapped to simple note ON/OFF events. Keep in mind though that MIDI has less bandwidth and data resolution compared to Open Sound Contol, so the new MIDI feature is meant as an convenient alternative in some cases, but TUIO still will be the primary messaging layer. Adding <midi config="midi_demo.xml" /> to reacTIVision.xml switches to MIDI mode and specifies the MIDI configuration files that contains the mappings and MIDI device selection. An example configuration file along with an example PD patch can be found in the midi folder. You can list all available MIDI devices with the "-l midi" option. Calibration and Distortion -------------------------Some tables, such as the reacTable are using a mirror in order to increase the area visible to the camera at a minimal distance. This mirror as well as a fish-eye lens unfortunately distort the image. reacTIVision can correct the distortion and alignment of the image. For the calibration print and place the provided calibration sheet on the table and adjust the grid points to the grid on the sheet. To calibrate reacTIVision switch to calibration mode hitting 'C' Use the keys A,D,W,X to move within grid, moving with the cursor keys will adjust the grid point 'O' resets the whole calibration grid, 'U' resets the selected point and 'K' reverts to the saved grid. To check if the distortion is working properly press 'R'. This will show the fully distorted live video image in the target window. Of course the distortion algorithm only corrects the found fiducial positions instead of the full image. Compilation ----------The source distribution includes projects for all three suppported

platforms and their respective build systems: Linux, Win32, MacOS X. Win32: A Visual Studio 2005 project as well as all the necessary libraries and headers (SDL, DsVideoLib) are included. The project should build right away without any additional configuration. Mac OS X: An Xcode project for Xcode version 2.4 or later is included. The build will require an installed SDL framework in order to compile properly. Linux: Call make to build the application, the distribution also inludes a spec file for the creation of an RPM package. Make sure you have the following libraries and headers installed: libSDL 1.2 and libdc1394 2.0 or later. License ------This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details. You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

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