critical(6)

NAME
critical - Draw a system showing self-organizing criticality

SYNOPSIS
critical [-display host:display.screen] [-foreground color] [-background color] [-window] [-root] [-mono] [-install] [-visual visual] [-delay seconds] [-random boolean] [-ncolors int] [-offset int]

DESCRIPTION
The critical program displays a self-organizing critical system that gradually emerges from chaos. critical performs a simulation on a two-dimensional array of integers. The array is initialized to random values. On each iteration, it draws a line to the array position with the greatest value. It then replaces that location and the eight neighboring locations with randomly-selected values. The lines are initially random, but over time a chaotic self-organizing system evolves: areas of the screen which happen to have lower values are less likely to be updated to new values, and so the line tends to avoid those areas. Eventually, the histogram of changes approaches the power-law curve typical of such systems. The simplest documented self-organizing system is the one-dimensional equivalent of critical. I heard about this algorithm second-hand: apparently there was an article in Scientific American describing it sometime in 1997.

OPTIONS
critical accepts the following options:

-window
    Draw on a newly-created window. This is the default.

-root
    Draw on the root window.

-mono
    If on a color display, pretend we're on a monochrome display.

-install
    Install a private colormap for the window.

-visual visual
    Specify which visual to use. Legal values are the name of a visual class, or the id number (decimal or hex) of a specific visual.

-delay usecs
    Number of microseconds to wait after drawing each line.

-random boolean
    Whether to use randomly selected colours rather than a cycle around the colour wheel.

-offset integer
    The maximum random radius increment to use.

-ncolors integer
    How many colors should be allocated in the color ramp (note that this value interacts with offset.)

-trail integer
    Length of the trail: between 5 and 100 is nice.

ENVIRONMENT

DISPLAY
    to get the default host and display number.

XENVIRONMENT
    to get the name of a resource file that overrides the global resources stored in the RESOURCE_MANAGER property.

SEE ALSO
X(1), xscreensaver(1) xscreensaver-command(1) xscreensaver-demo(1)

COPYRIGHT
Copyright © 1998 by Martin Pool. Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. No representations are made about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty.

AUTHOR
Martin Pool <mbp@humbug.org.au>, 1998-2000. Based in part on the XScreenSaver code by Jamie Zawinski <jwz@jwz.org>.