What is the Gametrak?

Wikipedia Review Music Research project using the Gametrak

Features

Cross-platform library based on HIDAPI to get raw events from the Gametrak (first you need to install a fresh version of HIDAPI from here)
Inspired by Libpointing
Get the position of each string end in Cartesian coordinates using metric units (mm)
Use callback functions instead of pooling
1€ filter embedded
Hotplugging
Supports calibration procedure
Easy and powerful configuration through URI
Easily connect several Gametraks to the same machine
Supports Pictrak mod by Jan Ciger

Minimal example

#include <libgametrak/GameTrak.h>
#include <iomanip>
#include <stdexcept>

using namespace gametrak ;

GameTrak *gt = 0 ;
TimeStamp::inttime last_time = 0 ;
bool button_pressed = false ;

void GameTrakCallback(void *context, 
             TimeStamp::inttime timestamp, 
             double leftx, double lefty, double leftz,
             double rightx, double righty, double rightz,
             bool button)  {
  if (!gt) return;
  double freq = 1/((timestamp - last_time) * 1.0E-9);
  std::cout << timestamp << " ns, " 
            << std::setw(7) << freq << " Hz, "
            << "Left: (" << std::setw(3) << leftx << ", " << std::setw(3) << lefty 
            << ", " << std::setw(3) << leftz << ") mm"
            << ", Right: (" << std::setw(3) << rightx << ", " << std::setw(3) << rightx
            << ", " << std::setw(3) << rightz << ") mm, "
            << "button: " << button << std::endl ;
  last_time = timestamp;
  button_pressed = button ;
}

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

    gt = GameTrak::create(argc>1?argv[1]:"") ;
    gt->setGameTrakCallback(GameTrakCallback) ;

    while (!button_pressed)
      GameTrak::idle(100) ; // milliseconds

    delete gt ;

  } catch (std::runtime_error e) {
    std::cerr << "Runtime error: " << e.what() << std::endl ;
  } catch (std::exception e) {
    std::cerr << "Exception: " << e.what() << std::endl ;
  }

  return 0 ;
}

URI documentation

uri are in the form "scheme:?arg1=value1&arg2=value2..."

Parameters can be set in arbitrary order. Parameters not set use default values.

Default parameters

The uri "" sets all parameters to default

Debug level

debugLevel (int) sets the debug level. Default is 0.
- 1 and above: lists connected Gametraks and their related information (e.g. path, serial number)
- 2 and above: display metric values for each degree of freedom
- 3 and above: display raw sensor information

Device parameters

devicePath (string) sets the device by its path. Default value: "". Use debugLevel 1 to know the path
serial_number (string) sets the device using its serial number. Default value: "". Only works with Pictrak.

Filtering

filter (bool) sets filtering on or off. Default value: true
mincutoff (double) sets € filter min cutoff frequency. Default value: 1.0
beta (double) sets 1€ filter beta value. Default value: 0.001
dcutoff (double) sets 1€ filter dcutoff. Default value: 1.0 (should not be changed)

Calibration

useCalibration (bool) defines if calibration is used. Default value: false
milt, milp, mill, mirt, mirp, mirl, malt, malp, mall, mart, marp, marl (double). Min (mi) and max (ma) values for left (l) and right (r) theta (t), phi (p) and L (l).

Mode (for data processing)

usePullMode (bool) defines if the datas are available using getters (true) or using a callback function (false). Default value: false

Connection

nbOfTryMax (int) defines a maximum number of try for connecting a Gametrak. Default value: -1 (infinite)

Installation

Works on Windows, OS X, Linux

There is no driver to install, simply install the last version of HIDAPI

Frame of reference

The picture below illustrates the origin and the axis used to locate each Gametrak pointer.

pib/libgametrak