epicycle man page on IRIX

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XScreenSaver(1)					  XScreenSaver(1)

NAME
       epicycle	 -  draws  a  point  moving around a circle which
       moves around a cicle which...

SYNOPSIS
       epicycle [-display host:display.screen] [-root]	[-window]
       [-mono]	[-install] [-noinstall] [-visual viz] [-colors N]
       [-foreground name] [-color-shift N] [-delay  microseconds]
       [-holdtime   seconds]   [-linewidth  N]	[-min_circles  N]
       [-max_circles N] [-min_speed number]  [-max_speed  number]
       [-harmonics N] [-timestep number] [-divisor_poisson proba_
       bility] [-size_factor_min number]  [-size_factor_max  num_
       ber]

DESCRIPTION
       The  epicycle program draws the path traced out by a point
       on the edge of a circle.	 That  circle  rotates	around	a
       point  on  the  rim  of another circle, and so on, several
       times.  The random curves produced can be simple	 or  com
       plex, convex or concave, but they are always closed curves
       (they never go in indefinitely).

       You can configure both the way the curves  are  drawn  and
       the  way in which the random sequence of circles is gener
       ated, either with command-line options or X resources.

OPTIONS
       -display host:display.screen
	       Specifies which X display we should use	(see  the
	       section DISPLAY NAMES in X(1) for more information
	       about this option).

       -root   Draw on the root window.

       -window Draw on	a  newly-created  window.   This  is  the
	       default.

       -mono   If   on	a  color  display,  pretend  we're  on	a
	       monochrome display.  If we're on a  mono	 display,
	       we have no choice.

       -install
	       Install a private colormap for the window.

       -noinstall
	       Don't install a private colormap for the window.

       -visual viz
	       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.	 Possible choices
	       include

	       default,	 best,	mono,  monochrome,  gray,   grey,
	       color,	 staticgray,	staticcolor,   truecolor,
	       grayscale,  greyscale,  pseudocolor,  directcolor,
	       number

	       If  a  decimal  or  hexadecimal	number	is  used,
	       XGetVisualInfo(3X)  is  consulted  to  obtain  the
	       required visual.

       -colors N
	       How many colors should be used (if possible).  The
	       colors are chosen randomly.

       -foreground name
	       With -mono, this	 option	 selects  the  foreground
	       colour.

       -delay microseconds
	       Specifies  the  delay  between  drawing successive
	       line segments of the path.   If you do not specify
	       -sync, some X servers may batch up several drawing
	       operations  together,  producing	 a  less   smooth
	       effect.	   This	 is  more  likely  to  happen  in
	       monochrome mode (on  monochrome	servers	 or  when
	       -mono is specified).

       -holdtime seconds
	       When  the figure is complete, epicycle pauses this
	       number of seconds.

       -linewidth N
	       Width in pixels of the body's track.    Specifying
	       values  greater than one may cause slower drawing.
	       The fastest value is  usually  zero,  meaning  one
	       pixel.

       -min_circles N
	       Smallest number of epicycles in the figure.

       -max_circles N
	       Largest number of epicycles in the figure.

       -min_speed number
	       Smallest possible value for the base speed of rev
	       olution of the epicycles.  The  actual  speeds  of
	       the  epicycles  vary from this down to min_speed /
	       harmonics.

       -max_speed number
	       Smallest possible value for the base speed of rev
	       olution of the epicycles.

       -harmonics N
	       Number  of  possible  harmonics;	 the  larger this
	       value is, the greater the possible variety of pos
	       sible speeds of epicycle.

       -timestep number
	       Decreasing this value will reduce the distance the
	       body moves for each line segment, possibly produc
	       ing  a smoother figure.	Increasing it may produce
	       faster results.

       -divisor_poisson probability
	       Each epicycle rotates at a rate which is a  factor
	       of  the base speed.  The speed of each epicycle is
	       the base speed divided by some integer  between	1
	       and  the	 value	of  the	 -harmonics option.  This
	       integer is decided by starting at 1 and tossing	a
	       biased coin.  For each consecutive head, the value
	       is incremented by one.  The integer  will  not  be
	       incremented  above  the	value  of  the -harmonics
	       option.	The argument of this option  decides  the
	       bias  of the coin; it is the probability that that
	       coin will produce a head at any given toss.

       -size_factor_min number
	       Epicycles are always at least this factor  smaller
	       than their parents.

       -size_factor_max number
	       Epicycles  are never more than this factor smaller
	       than their parents.

RESOURCES
	    Option	      Resource		     Default Value
	    ------	      --------		     -------------
	    -colors	      .colors		     100
	    -delay	      .delay		     1000
	    -holdtime	      .holdtime		     2
	    -linewidth	      .lineWidth	     4
	    -min_circles      .minCircles	     2
	    -max_circles      .maxCircles	     10
	    -min_speed	      .minSpeed		     0.003
	    -max_speed	      .maxSpeed		     0.005
	    -harmonics	      .harmonics	     8
	    -timestep	      .timestep		     1.0
	    -divisor_poisson  .divisorPoisson	     0.4
	    -size_factor_min  .sizeFactorMin	     1.05
	    -size_factor_max  .sizeFactorMax	     2.05
			      .timestepCoarseFactor  1.0

       Before the drawing of the figure is begun,  a  preliminary
       calculation  of	the  path  is  done in order to scale the
       radii of the epicycles so as to	fit  the  figure  on  the
       screen or window.  For the sake of speed, This calculation
       is done with a larger timestep than  the	 actual	 drawing.
       The  time-step  used  is the value of the -timestep option
       multiplied  by  the  timestepCoarseFactor  resource.   The
       default value of 1 will almost always work fast enough and
       so this	resource  is  not  available  as  a  command-line
       option.

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

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

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

COPYRIGHT
       Copyright    1998,  James  Youngman.   Permission to use,
       copy, modify, distribute, and sell this software	 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 provided "as is"  without
       express or implied warranty.

AUTHOR
       James Youngman <jay@gnu.org>, April 1998.

X Version 11		    27-Apr-97		  XScreenSaver(1)
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