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] [-mono] [-in‐
11       stall]  [-noinstall]  [-visual  viz]  [-colors  N]  [-foreground  name]
12       [-color-shift N] [-delay microseconds] [-holdtime seconds]  [-linewidth
13       N]  [-min_circles  N]  [-max_circles N] [-min_speed number] [-max_speed
14       number] [-harmonics N] [-timestep number]  [-divisor_poisson  probabil‐
15       ity] [-size_factor_min number] [-size_factor_max number] [-fps]
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DESCRIPTION

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

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

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

HISTORY

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

150       The  colour  selection  is re-done for every figure.  This may generate
151       too much network traffic for this program to work  well  over  slow  or
152       long links.
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155       Copyright  ©  1998,  James  Youngman.  Permission to use, copy, modify,
156       distribute, and sell this software and its documentation for  any  pur‐
157       pose  is  hereby granted without fee, provided that the above copyright
158       notice appear in all copies and that both  that  copyright  notice  and
159       this  permission  notice appear in supporting documentation.  No repre‐
160       sentations are made about the suitability of this software for any pur‐
161       pose.  It is provided "as is" without express or implied warranty.
162

AUTHOR

164       James Youngman <jay@gnu.org>, April 1998.
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168X Version 11               6.02-4.fc35 (09-Nov-2021)              epicycle(6x)
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