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       substrate - Grow crystal-like lines on a computational substrate


       substrate   [-display   host:display.screen]   [-foreground   color]  [-background  color]
       [-wireframe] [-max-cycles cyclecount] [-growth-delay delayms] [-initial-cracks numinitial]
       [-max-cracks nummax] [-sand-grains numgrains] [-circle-percent circlepercent] [-fps]


       Lines like crystals grow on a computational substrate.  A simple perpendicular growth rule
       creates  intricate  city-like  structures.   Optionally,  cracks  may  also  be  circular,
       producing  a  cityscape  more  familiar  to  places  for which city planning is a distant,
       theoretical concern.

       Ported from the code by j.tarbell at


       substrate accepts the following options:

       -wireframe (Default: False)
               Don't draw sand-painting colored effects, only make a wireframe.

       -max-cycles cyclecount (Default: 10000)
               Maximum number of growth cycles before restarting.  The higher this is,  the  more
               complex the art.

       -growth-delay delayms (Default: 18000)
               Delay  in ms between growth cycles.  More delay, slower (but smoother and less CPU
               intensive) art.

       -initial-cracks numinitial (Default: 3)
               Initial number of cracks in the substrate

       -max-cracks nummax (Default: 100)
               Maximum number of cracks in the substrate at a single time

       -sand-grains numgrains (Default: 64)
               Number of sand grains dropped during coloring.  More grains cause a denser  colour
               but use more cpu power.

       -circle-percent circlepercent (Default: 0)
               The percentage of the cracks will be circular.

       -fps    Display the current frame rate and CPU load.


       DISPLAY to get the default host and display number.

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


       X(1), xscreensaver(1)


       Copyright     ©      2003      by      J.      Tarbell      (,

       Ported to XScreensaver 2004 by Mike Kershaw (


       J. Tarbell <>, Jun-03

       Mike Kershaw <>, Oct-04