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The OpenGL Demo
  the sensor

  the result

    The Flock of Birds is a motion tracking device that allows you to get position and orientation information for up to 7 sensors.  

    You could use this information to run a real-time simulation in OpenGL, or write the data out to a file to be used as motion capture data in Maya.

  • Download the sgiflock software to your home directory.  This software was written by Greg Schmidt.
  • Install the software following Greg's instructions (read the README files)
  • You will compile a few drivers with the included Makefiles, and create a library directory (usually, /u/username/lib) to copy the *.so files into.
  • You must set the path to this new library directory.  Type:
    setenv LD_LIBRARYN32_PATH /u/username/lib
    OR add the line to your .cshrc if you will use the flock a lot.
How the Flock of Birds Works
  • The flock of birds works by using magnetic fields.
  • There is a large black transmitter sitting on a stand that produces a magnetic field.  
  • We have an array of seven sensors that can each sense changes in the magnetic field to report position and orientation information.
  • The sensors will not work near metal or magnets (including computer monitors and speakers).  They also don't do well right next to each other.
  • The transmitter is elevated to utilize all of it's three-dimensional range.  It has an effective range of about 10 feet, although you will notice distortion near the edge. 
  • You can expect to get roughly 100 samples/second when using one sensor.
  • To use the flock, you must write C code using the provided drivers.
Using the Flock of Birds
  • First get your setup ready by attaching sensors and orienting the transmitter in the desired direction.
  • We currently have seven sensors available for use.  PLEASE keep the area clean by coiling the wire up when you are done with the sensors.
  • Check to see that the A/B switch is set to B for the SGI (gurgi).
  • Switch on the power source under the A/B Switch.
  • Switch on the Flock Hardware by pressing the blue button.
  • Run your executable.
  • Get used to how the sgiflock class works, and check the documentation as well.  This provides some idea as to the class constructors and methods.  Also see the demos section below.
  • When you are ready to turn off the hardware, power down in the opposite order that you turned the units on.  DO NOT LEAVE THE UNIT ON OVER NIGHT!
  • Note: If the flock refuses to take samples, then the system needs to be reset by powering down and then powering back up.  (Hint: make sure you gracefully shut down the data stream when exiting your program).  
  • Compile the demo programs written by Greg Schmidt.
  • These demos show the use of the sgiflock object and its constructors and methods, and show various outputs for various numbers of sensors.
  • You can get output as
    • position (x, y, z)
    • angle
    • matrix
    • quaternion
  • This output can be used for real-time programs, or can be written to a file for use as motion capture data in Maya.  You just have to code it.
  • In addition to Greg Schmidt's demos, I have written a simple demo using OpenGL to translate and rotate an RGB color cube based on the real world values given by sensor 1.

    Now you know how to use the Flock of Birds.

    Any questions?  Just ask! 

    Chris Coleman


Created 2/01 by Chris Coleman
Visualization Laboratory, Texas A&M University