XScreenSaver(1)
NAME
attraction - interactions of opposing forces
SYNOPSIS
attraction [-display host:display.screen] [-foreground
color] [-background 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] [-mouse]
[-no-mouse] [-mouse-size]
DESCRIPTION
The attraction program has several visually different
modes of operation, all of which are based on the interac-
tions 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.
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 number randomly. Default 0. Between 3
and 15 works best.
-threshold integer
The distance (in pixels) from each particle at
which the attractive 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 control points.
In filled-splines mode, the splines are filled in
instead of being outlines. This is most interest-
ing in color.
In tails mode, the path which each particle fol-
lows is indicated 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
100. This has no effect in balls mode. If seg-
ments 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 seg-
ments 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 num-
ber 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.
-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 resistance. Values higher than 1
aren't interesting; lower values cause less
motion.
One interesting thing to try is
attraction -viscosity 0.8 -points 75 \
-mouse -geometry =500x500
Give it a few seconds to settle down into a stable
clump, and then move the mouse through it to make
"waves".
-mouse This will cause the mouse to be considered a con-
trol point; it will not be drawn, but it will
influence the other points, so you can wave the
mouse and influence the images being created.
-no-mouse
Turns off -mouse.
-mouse-size integer
In -mouse mode, this sets the mass of the mouse
(analagously to the -size parameter.)
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_MAN-
AGER property.
SEE ALSO
X(1) xscreensaver(1)
COPYRIGHT
Copyright (C) 1992, 1993, 1997 by Jamie Zawinski. Permis-
sion to use, copy, modify, distribute, and sell this soft-
ware 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 pro-
vided "as is" without express or implied warranty.
AUTHOR
Jamie Zawinski lt;jwz@netscape.com, 13-aug-92.
Viscosity and mouse support by Philip Edward Cutone, III.