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]
11       [-install]  [-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.
39
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,
53               directcolor, number
54
55               If  a decimal or hexadecimal number is used, XGetVisualInfo(3X)
56               is consulted to obtain the required visual.
57
58       -colors N
59               How many colors should be used (if possible).  The  colors  are
60               chosen randomly.
61
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.
86
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.
91
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.
115
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.
125

RESOURCES

127       Option            Resource               Default Value
128       ------            --------               -------------
129       -colors           .colors                100
130       -delay            .delay                 1000
131       -holdtime         .holdtime              2
132       -linewidth        .lineWidth             4
133       -min_circles      .minCircles            2
134       -max_circles      .maxCircles            10
135       -min_speed        .minSpeed              0.003
136       -max_speed        .maxSpeed              0.005
137       -harmonics        .harmonics             8
138       -timestep         .timestep              1.0
139       -divisor_poisson  .divisorPoisson        0.4
140       -size_factor_min  .sizeFactorMin         1.05
141       -size_factor_max  .sizeFactorMax         2.05
142                         .timestepCoarseFactor  1.0
143       Before the drawing of the figure is begun, a preliminary calculation of
144       the  path is done in order to scale the radii of the epicycles so as to
145       fit the figure on the screen or window.  For the sake  of  speed,  This
146       calculation  is  done  with  a larger timestep than the actual drawing.
147       The time-step used is the value of the -timestep option  multiplied  by
148       the  timestepCoarseFactor resource.  The default value of 1 will almost
149       always work fast enough and so this resource is not available as a com‐
150       mand-line option.
151

USER INTERFACE

153       The  program runs mostly without user interaction.  When running on the
154       root window, no input is accepted.  When running in its own window, the
155       program  will  exit  if  mouse button 3 is pressed.  If any other mouse
156       button is pressed, the current figure will  be  abandoned  and  another
157       will be started.
158

HISTORY

160       The geometry of epicycles was perfected by Hipparchus of Rhodes at some
161       time around 125 B.C., 185 years  after  the  birth  of  Aristarchus  of
162       Samos,  the  inventor  of  the heliocentric universe model.  Hipparchus
163       applied epicycles to the Sun and the Moon.  Ptolemy of Alexandria  went
164       on  to  apply  them  to what was then the known universe, at around 150
165       A.D.  Copernicus went on to apply them to the heliocentric model at the
166       beginning  of  the  sixteenth century.  Johannes Kepler discovered that
167       the planets actually move in elliptical  orbits  in  about  1602.   The
168       inverse-square law of gravity was suggested by Boulliau in 1645.  Isaac
169       Newton's Principia Mathematica was published in 1687, and  proved  that
170       Kepler's laws derived from Newtonian gravitation.
171

BUGS

173       The  colour  selection  is re-done for every figure.  This may generate
174       too much network traffic for this program to work  well  over  slow  or
175       long links.
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178       Copyright  ©  1998,  James  Youngman.  Permission to use, copy, modify,
179       distribute, and sell this software and its documentation for  any  pur‐
180       pose  is  hereby granted without fee, provided that the above copyright
181       notice appear in all copies and that both  that  copyright  notice  and
182       this  permission  notice appear in supporting documentation.  No repre‐
183       sentations are made about the suitability of this software for any pur‐
184       pose.  It is provided "as is" without express or implied warranty.
185

AUTHOR

187       James Youngman <jay@gnu.org>, April 1998.
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191X Version 11               5.42-1.fc29 (30-Dec-2018)              epicycle(6x)
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