1epicycle(6x)                  XScreenSaver manual                 epicycle(6x)
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NAME

6       epicycle  -  draws  a point moving around a circle which moves around a
7       cicle which...
8

SYNOPSIS

10       epicycle [--display  host:display.screen]  [--root]  [--window-id  num‐
11       ber][--window]   [--mono]   [--install]  [--noinstall]  [--visual  viz]
12       [--colors N] [--foreground name] [--color-shift N]  [--delay  microsec‐
13       onds]   [--holdtime   seconds]   [--linewidth   N]   [--min_circles  N]
14       [--max_circles N] [--min_speed number] [--max_speed number]  [--harmon‐
15       ics N] [--timestep number] [--divisor_poisson probability] [--size_fac‐
16       tor_min number] [--size_factor_max number] [--fps]
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DESCRIPTION

19       The epicycle program draws the path traced out by a point on  the  edge
20       of  a circle.  That circle rotates around a point on the rim of another
21       circle, and so on, several times.  The random curves  produced  can  be
22       simple or complex, convex or concave, but they are always closed curves
23       (they never go in indefinitely).
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25       You can configure both the way the curves are  drawn  and  the  way  in
26       which the random sequence of circles is generated, either with command-
27       line options or X resources.
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OPTIONS

30       --display host:display.screen
31               Specifies which X display we should use (see the  section  DIS‐
32               PLAY NAMES in X(1) for more information about this option).
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34       --root  Draw on the root window.
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36       --window-id number
37               Draw on the specified window.
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39       --window
40               Draw on a newly-created window.  This is the default.
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42       --mono  If  on  a color display, pretend we're on a monochrome display.
43               If we're on a mono display, we have no choice.
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45       --install
46               Install a private colormap for the window.
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48       --noinstall
49               Don't install a private colormap for the window.
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51       --visual viz
52               Specify which visual to use.  Legal values are the  name  of  a
53               visual  class,  or the id number (decimal or hex) of a specific
54               visual.  Possible choices include
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56               default, best, mono, monochrome, gray, grey, color, staticgray,
57               staticcolor,  truecolor, grayscale, greyscale, pseudocolor, di‐
58               rectcolor, number
59
60               If a decimal or hexadecimal number is used,  XGetVisualInfo(3X)
61               is consulted to obtain the required visual.
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63       --colors N
64               How  many  colors should be used (if possible).  The colors are
65               chosen randomly.
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67       --foreground name
68               With --mono, this option selects the foreground colour.
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70       --delay microseconds
71               Specifies the delay between drawing successive line segments of
72               the  path.    If  you  do not specify -sync, some X servers may
73               batch up several drawing operations together, producing a  less
74               smooth  effect.    This  is more likely to happen in monochrome
75               mode (on monochrome servers or when --mono is specified).
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77       --holdtime seconds
78               When the figure is complete, epicycle  pauses  this  number  of
79               seconds.
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81       --linewidth N
82               Width  in  pixels  of  the  body's  track.    Specifying values
83               greater than one may cause slower drawing.   The fastest  value
84               is usually zero, meaning one pixel.
85
86       --min_circles N
87               Smallest number of epicycles in the figure.
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89       --max_circles N
90               Largest number of epicycles in the figure.
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92       --min_speed number
93               Smallest possible value for the base speed of revolution of the
94               epicycles.  The actual speeds of the epicycles vary  from  this
95               down to min_speed / harmonics.
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97       --max_speed number
98               Smallest possible value for the base speed of revolution of the
99               epicycles.
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101       --harmonics N
102               Number of possible harmonics; the larger  this  value  is,  the
103               greater the possible variety of possible speeds of epicycle.
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105       --timestep number
106               Decreasing  this  value will reduce the distance the body moves
107               for each line segment, possibly producing  a  smoother  figure.
108               Increasing it may produce faster results.
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110       --divisor_poisson probability
111               Each  epicycle  rotates at a rate which is a factor of the base
112               speed.  The speed of each epicycle is the base speed divided by
113               some integer between 1 and the value of the --harmonics option.
114               This integer is decided by starting at 1 and tossing  a  biased
115               coin.   For  each consecutive head, the value is incremented by
116               one.  The integer will not be incremented above  the  value  of
117               the  --harmonics  option.   The argument of this option decides
118               the bias of the coin; it is the probability that that coin will
119               produce a head at any given toss.
120
121       --size_factor_min number
122               Epicycles  are  always  at least this factor smaller than their
123               parents.
124
125       --size_factor_max number
126               Epicycles are never more than this factor  smaller  than  their
127               parents.
128
129       --fps   Display the current frame rate and CPU load.  --timestep option
130               multiplied by the timestepCoarseFactor resource.   The  default
131               value  of 1 will almost always work fast enough and so this re‐
132               source is not available as a command-line option.
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USER INTERFACE

135       The program runs mostly without user interaction.  When running on  the
136       root window, no input is accepted.  When running in its own window, the
137       program will exit if mouse button 3 is pressed.   If  any  other  mouse
138       button  is  pressed,  the  current figure will be abandoned and another
139       will be started.
140

HISTORY

142       The geometry of epicycles was perfected by Hipparchus of Rhodes at some
143       time  around  125  B.C.,  185  years  after the birth of Aristarchus of
144       Samos, the inventor of the heliocentric universe model.  Hipparchus ap‐
145       plied epicycles to the Sun and the Moon.  Ptolemy of Alexandria went on
146       to apply them to what was then the known universe, at around  150  A.D.
147       Copernicus  went  on to apply them to the heliocentric model at the be‐
148       ginning of the sixteenth century.  Johannes Kepler discovered that  the
149       planets actually move in elliptical orbits in about 1602.  The inverse-
150       square law of gravity was suggested by Boulliau in  1645.   Isaac  New‐
151       ton's  Principia Mathematica was published in 1687, and proved that Ke‐
152       pler's laws derived from Newtonian gravitation.
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BUGS

155       The colour selection is re-done for every figure.   This  may  generate
156       too  much  network  traffic  for this program to work well over slow or
157       long links.
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ENVIRONMENT

160       DISPLAY to get the default host and display number.
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162       XENVIRONMENT
163               to get the name of a resource file that  overrides  the  global
164               resources stored in the RESOURCE_MANAGER property.
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166       XSCREENSAVER_WINDOW
167               The window ID to use with --root.
168

SEE ALSO

170       X(1), xscreensaver(1)
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173       Copyright  ©  1998,  James  Youngman.  Permission to use, copy, modify,
174       distribute, and sell this software and its documentation for  any  pur‐
175       pose  is  hereby granted without fee, provided that the above copyright
176       notice appear in all copies and that both  that  copyright  notice  and
177       this  permission  notice appear in supporting documentation.  No repre‐
178       sentations are made about the suitability of this software for any pur‐
179       pose.  It is provided "as is" without express or implied warranty.
180

AUTHOR

182       James Youngman <jay@gnu.org>, April 1998.
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186X Version 11               6.08-1.fc39 (17-Oct-2023)              epicycle(6x)
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