Requiem for Flocking Orchestra

Sample Images
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Sample Movies
Click the frame images to see the movies.

MPEG-4, 3.8MB

MPEG-4, 3.0MB
Please refer to the web site of Flocking Orchestra to download the software that runs on MacOS X 10.3.
Please check the movie then you can learn how to fold a paper crane.

MPEG-4, 5.8MB
This is an interactive installation of a type of media art (or digital art) besed on Flocking Orchestra for 60th anniversary of the end of World War II, especially for atomic bombing in Hiroshima. We implemented this installation with our deepest hope for the world to be peaceful.

The True Story of Sadako

This collaborative work by Daniel Bisig in Switzerland and Tatsuo Unemi in Japan implements a mathematical model of flocking behavior that was developed in artificial life research. In its current form, it is inspired by a true story of a girl who has died from leukemia 50 years ago in Hiroshima. Her name is Sadako. She was exposed to atomic bombing when she was two years old. Her health was perfect during the nine years following the bombing. But all of the sudden she had to be hospitalised during February 1955. Lying in a hospital bed, she folding many paper cranes. According to a Japanese legend, by folding one thousand paper cranes, one's wish becomes true. Sadly, her own wish remained unfulfilled and her life ended 50 years ago.

The images which texture the walls of the virtual space stem from photographs that one of the authors shot in 2003 at the Peace Memorial Park in Hiroshima during a funeral ceremony of his friend. The image of the back wall depicts the Children's Peace Monument which was established in 1958 by school classmates of Sadako. Every year, many groups of school students fold paper cranes and bring them to this monument where they swear to contribute to a more peaceful world.

You can learn more about the story from the web site of Kids Peace Station organized by Hiroshima Peace Memorial Museum.

Technical Aspects

More than 120 moving paper cranes are displayed on the screen. A camera is mounted on the upper edge of the screen. It records the visitor's actions and transforms these into input for the installation. A sequence of camera images are analyzed in order to determine the user's motions. The flocking cranes respond to these motions. Each agent plays a MIDI instrument. The agent's behavior within the virtual world influences the instrument's control. By influencing the agent's behavior, users can control the acoustic output of the installation as if they were conducting an orchestra.

Flocking behavior is an example of a complex phenomena that is exhibited by animals. This phenomena forms on of the central research issues in artificial life together with other phenomena such as evolution, growth, learning etc. The very first simulation of flocking behavior entitled BOIDS was developed by computer graphics specialist Craig Reynolds in order to create a believable animation of birds. Since then, flocking algorithms have become a well established technique in Hollywood films.

Recent progress in computer hardware made it possible to implement flocking based 3D animations of acceptable performance on a personal computer. Furthermore, the availability of cheap video cameras and motion detection solutions helped to pave the way for this installation.

In the classical BOIDS system the movement and orientation of each agent is calculated at each simulation step. The target orientation results from the accumulation of the following three forces: collision avoidance, movement towards the center of gravity of neighboring agents, velocity alignment with neighboring agents. The agent capability to turn towards this target orientation is limited in its velocity and steering angle.

In order to make the flock respond to user interaction, we introduced a fourth force which creates attraction towards user movements. This force pushes the agent towards to front part of the virtual space. Each agent possesses a limited viewing volume that extends from its position towards the front of the screen. The agent is attracted towards the center of movement which is perceived within it's field of view. In order to render the effects of interaction on agent behavior more apparent, a fifth force was introduced, which pushed the agents away from the front plane if it doesn't perceive any user motion.

Since the inventions of the BOIDS system, several artistic applications of flocking behavior have been developed by artists and scientists. Some of these applications rely on flocking in order to create music. As Tim Blackwell, one of the creators of such a system, pointed out, both man made music and flocking based music possess some similarity since they both can produce fractal sound structures.

Our installation is capable of producing natural sounding music as well. By adapting the configuration and types of instruments, harmonic rules and rhythms, it can generate a wide variety of musical styles such as jazz, rock, classic, and so on. In this particular version of the installation, the instrumentation consists of an electric piano, and orchestra harp and a standard drum set. The x, y, and z co-ordinates of each agent's position map into pan, pitch, and velocity of the sound it generates. The rhythm results from a rule set which controls when each agent is allowed to play a note it's instrument. The current rule set assign a probability of playing a note which is proportional to the agents velocity.

The agents are divided into two groups. One group plays melodic tones with electric piano and orchestra harp, and the other group plays percussive instruments. Each group forms its own flock. The two flocks interact with each other in order to avoid on collisions. The amplitude ratio of the two melodic instruments is proportional to the amount of motion detected. In the absence of motion, the electric piano dominates, whereas the orchestra harp becomes active as motion increases. In a similar way, the amplitudes of the percussive instruments are modified. Thanks to this method, the flock's reaction to user interaction is not only visible but also clearly audible.


Any comment, suggestion, proposal, essay inspired, and so on are welcome. Please send them to
May 25th, 2005. © 2005 Tatsuo Unemi & Daniel Bisig