NAME

       boids - simulate a flock of android birds from Brooklyn

SYNOPSIS

       boids -help
         or
       boids  [-width  integer]  [-height integer] [-num integer]
              [-steps integer] [-seed  integer]  [-angle  double]
              [-vangle  double]  [-rcopy  double] [-rcent double]
              [-rvoid double]  [-rviso  double]  [-wcopy  double]
              [-wcent  double]  [-wvoid  double]  [-wviso double]
              [-wrand double] [-dt double] [-ddt  double]  [-minv
              double] [-len integer] [-psdump] [-inv] [-mag inte-
              ger] [-term string]

DESCRIPTION

       Simulate a flock of boids according to rules  that  deter-
       mine their individual behaviors as well as the ``physics''
       of their universe.  A boid greedily attempts to apply four
       rules  with  respect  to its neighbors: it wants to fly in
       the same direction, be in the center of the local  cluster
       of boids, avoid collisions with boids too close, and main-
       tain a clear view ahead by  skirting  around  others  that
       block  its  view.  Changing these rules can make the boids
       behave like birds, gnats, bees, fish, or  magnetic  parti-
       cles.   See the RULES section of the manual pages for more
       details.

OPTIONS

       -width integer
              Width of the plot in pixels.

       -height integer
              Height of the plot in pixels.

       -num integer
              Number of boids.

       -steps integer
              Number of simulated steps.

       -seed integer
              Random seed for initial state.

       -angle double
              Number of viewing degrees.

       -vangle double
              Visual avoidance angle.

       -rcopy double
              Radius for copy vector.


       -rcent double
              Radius for centroid vector.

       -rvoid double
              Radius for avoidance vector.

       -rviso double
              Radius for visual avoidance vector.

       -wcopy double
              Weight for copy vector.

       -wcent double
              Weight for centroid vector.

       -wvoid double
              Weight for avoidance vector.

       -wviso double
              Weight for visual avoidance vector.

       -wrand double
              Weight for random vector.

       -dt double
              Time-step increment.

       -ddt double
              Momentum factor (0 < ddt < 1).

       -minv double
              Minimum velocity.

       -len integer
              Tail length.

       -psdump
              Dump PS at the very end?

       -inv   Invert all colors?

       -mag integer
              Magnification factor.

       -term string
              How to plot points.

RULES

       All of the rules have a weight option and a radius option.
       The radius option specifies how close a boid need to be to
       another in order for the  rule  to  be  acted  upon.   The
       weight  is  used  when  combining all of the rules actions
       into a single new velocity vector.


       The four rules can be simply described as follows:

          Centering: move towards the center of any boids in my
                     viewing area.

          Copying: attempt to move in the average direction of
                   that all boids that can be seen are moving
                   in.

          Avoidance: ``Please don't stand so close to me.''
                       Move away from any close flyers.

          Visual: move in such a way that the bonehead
                  obstructing your view no longer interferes.

       The four rules are then normalized and added  together  to
       make  the  next velocity vector of the boid.  All radii in
       the rules are in terms of pixels.

       You may wish to try turning on and off different  combina-
       tions of the rules to see how the boids' behaviors change.
       For example, if you turn off the avoidance rule,  increase
       the  centering radius and weight, and increase the viewing
       angle to nearly 360 degrees, then the  boids  will  behave
       like  a  pack  of  wolves fighting over the center.  Other
       changes can yield similar surprises.

BUGS

       No sanity checks are performed to make sure  that  any  of
       the options make sense.

AUTHOR

       Copyright (c) 1997, Gary William Flake.

       Permission  granted  for any use according to the standard
       GNU ``copyleft'' agreement provided that the author's com-
       ments  are  neither  modified nor removed.  No warranty is
       given or implied.