XScreenSaver(1)XScreenSaver(1)NAMEattraction - interactions of opposing forces
SYNOPSISattraction [-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] [-walls] [-nowalls] [-maxspeed]
[-nomaxspeed] [-correct-bounce] [-fast-bounce]
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.
OPTIONSattraction 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.)
-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 tendancy 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 circum
stances, 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.
-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".
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 ALSOX(1), xscreensaver(1)COPYRIGHT
Copyright 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 <jwz@jwz.org>, 13-aug-92.
Viscosity and mouse 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 14-Jun-97 XScreenSaver(1)
