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attraction(6)		      XScreenSaver manual		 attraction(6)

NAME
       attraction - interactions of opposing forces

SYNOPSIS
       attraction  [-display  host:display.screen] [-foreground	color] [-back-
       ground color] [-window] [-root]	[-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]

DESCRIPTION
       The  attraction	program	has several visually different modes of	opera-
       tion, 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 be-
       gin to repel each other.	 The attraction/repulsion is  proportional  to
       the distance between any	two particles.

OPTIONS
       attraction 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.

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

       -threshold integer
	       The distance (in	pixels)	from each particle at  which  the  at-
	       tractive	force becomes repulsive.  Default 100.

       -mode balls | 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 con-
	       trol 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 indi-
	       cated by	a worm-like trail, whose length	is controlled  by  the
	       segments	parameter.

       -size integer
	       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.

       -segments integer
	       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.)

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

       -color-shift int
	       If on a color display, the color	of the line segments or	 poly-
	       gons 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  ef-
	       fect in balls mode.

       -radius The  size  in pixels of the circle on which the points are ini-
	       tially 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  ac-
	       cording	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.

       -vx pixels

       -vy pixels
	       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.

       -vmult float
	       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.

       -viscosity float
	       This sets the viscosity of the hypothetical fluid through which
	       the  control  points  move; the default is 1, meaning no	resis-
	       tance.  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 re-
	       verses its velocity.  This works	fine for most cases, but under
	       some circumstances, the simplification can lead to annoying ef-
	       fects.

       -correct-bounce
	       Uses a more intelligent bouncing	algorithm.  This method	 actu-
	       ally  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.

       -graphmode none | 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.

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)

COPYRIGHT
       Copyright  (C)  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  no-
       tice 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
       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		      5.44 (20-Mar-2020)		 attraction(6)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | ENVIRONMENT | SEE ALSO | COPYRIGHT | AUTHOR

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