attraction - interactions of opposing forces

       Jamie Zawinski <jwz@jwz.org>, 13-aug-92.

       Viscosity support by Philip Edward Cutone, III.

       Walls, speed limit options, new bouncing, graphs, and tail mode fix by Matthew Strait. 31 March 2001

X Version 11                                   6.08 (10-Oct-2023)                                 attraction(6x)

       Copyright © 1992, 1993, 1997 by Jamie Zawinski.  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.

       The attraction program has several visually different modes of operation, all of which are based  on  the
       interactions of a set of control points which attract each other up to a certain distance, and then begin
       to repel each other.  The attraction/repulsion is proportional to the distance between any two particles.

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.

       XSCREENSAVER_WINDOW
               The window ID to use with --root.

       attraction - interactions of opposing forces

attraction accepts the following options:

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

       --root  Draw on the root window.

       --window-idnumber
               Draw on the specified window.

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

       --install
               Install a private colormap for the window.

       --visualvisual
               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.

       --pointsinteger
               How many control points should be used, or 0 to select the number randomly.  Default 0.   Between
               3 and 15 works best.

       --thresholdinteger
               The  distance  (in  pixels)  from  each particle at which the attractive force becomes repulsive.
               Default 100.

       --modeballs|lines|polygons|tails|splines|filled-splines
               In balls mode (the default) the control points are drawn  as  filled  circles.   The  larger  the
               circle, the more massive the particle.

               In  lines  mode, the control points are connected by straight lines; the effect is something like
               qix.

               In polygons mode, the control points are connected by straight lines, and  filled  in.   This  is
               most interesting in color.

               In splines mode, a closed spline is interpolated from the control points.

               In  filled-splines  mode,  the  splines  are  filled  in instead of being outlines.  This is most
               interesting in color.

               In tails mode, the path which each particle follows is indicated  by  a  worm-like  trail,  whose
               length is controlled by the segments parameter.

       --sizeinteger
               The  size  of  the balls in pixels, or 0, meaning to select the sizes randomly (the default.)  If
               this is specified, then all balls will be the same size.  This option has an effect in all modes,
               since the ``size'' of the balls controls their mass.

       --segmentsinteger
               If in lines or polygons mode, how many sets of line segments or polygons should be drawn. Default
               500.  This has no effect in balls mode.  If segments is 0, then no segments will ever  be  erased
               (this is only useful in color.)

       --delaymicroseconds
               How much of a delay should be introduced between steps of the animation.  Default 10000, or about
               0.01 seconds.

       --color-shiftint
               If  on  a  color display, the color of the line segments or polygons will cycle through the color
               map.  This specifies how many lines will be drawn before a new color is chosen.   (When  a  small
               number  of colors are available, increasing this value will yield smoother transitions.)  Default
               3.  This has no effect in balls mode.

       --radius
               The size in pixels of the circle on which the points are initially positioned.   The  default  is
               slightly smaller than the size of the window.

       --glow  This is consulted only in balls mode.  If this is specified, then the saturation of the colors of
               the points will vary according to their current acceleration.  This has the effect that the balls
               flare brighter when they are reacting to each other most strongly.

               In  glow  mode,  all  of  the  balls will be drawn the same (random) color, modulo the saturation
               shifts.  In non-glow mode, the balls will each be drawn in a random color that doesn't change.

       --noglow
               Don't do ``glowing.''  This is the default.

       --vxpixels--vypixels
               Initial velocity of the balls.  This has no effect in --orbit mode.

       --orbit Make the initial force on each ball be tangential to the  circle  on  which  they  are  initially
               placed,  with the right velocity to hold them in orbit about each other.  After a while, roundoff
               errors will cause the orbit to decay.

       --vmultfloat
               In orbit mode, the initial velocity of the balls is multiplied by this; a number less than 1 will
               make the balls pull closer together, and a larger number will make them move apart.  The  default
               is 0.9, meaning a slight inward pull.

       --viscosityfloat
               This  sets  the  viscosity  of  the hypothetical fluid through which the control points move; the
               default is 1, meaning no resistance.  Values higher than 1 aren't interesting; lower values cause
               less motion.

               One interesting thing to try is

                    attraction -viscosity 0.8 -points 300 \
                    -size 10 -geometry =500x500

               Give it a few seconds to settle down into a stable clump,  and  then  move  the  drag  the  mouse
               through it to make "waves".

       --nowalls
               This  will cause the balls to continue on past the edge of the screen or window.  They will still
               be kept track of and can come back.

       --walls This will cause the balls to bounce when they get to the edge of the screen or window.   This  is
               the default behavior.

       --maxspeed
               Imposes  a maximum speed (default).  If a ball ends up going faster than this, it will be treated
               as though there were .9  viscosity until it is  under  the  limit.  This  stops  the  balls  from
               continually  accelerating  (which  they have a tendency to do), but also causes balls moving very
               fast to tend to clump in the lower right corner.

       --nomaxspeed
               If this is specified, no maximum speed is set for the balls.

       --fast-bounce
               Uses the old, simple bouncing algorithm (default).  This simply moves any ball  that  is  out  of
               bounds  back to a wall and reverses its velocity.  This works fine for most cases, but under some
               circumstances, the simplification can lead to annoying effects.

       --correct-bounce
               Uses a more intelligent bouncing algorithm.  This method actually  reflects  the  balls  off  the
               walls  until they are within bounds.  This can be slow if balls are bouncing a whole lot, perhaps
               because of -nomaxspeed.

       --graphmodenone|x|y|both|speed
               For "x", "y", and "both", displays the given velocities of each ball as a bar graph in  the  same
               window as the balls.  For "speed", displays the total speed of each ball.  Default is "none".

       --fps   Display the current frame rate and CPU load.

X(1), xscreensaver(1)

attraction  [--display host:display.screen] [--foreground color] [--background color] [--window] [--root]
       [--window-id number][--mono] [--install] [--visual visual] [--points int] [--threshold int] [--mode balls
       | lines | polygons | splines | filled-splines | tails ] [--size int]  [--segments  int]  [--delay  usecs]
       [--color-shift  int]  [--radius  int]  [--vx  int]  [--vy int] [--glow] [--noglow] [--orbit] [--viscosity
       float] [--walls] [--nowalls] [--maxspeed] [--nomaxspeed] [--correct-bounce] [--fast-bounce] [--fps]