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diff --git a/hacks/epicycle.man b/hacks/epicycle.man new file mode 100644 index 0000000..290884f --- /dev/null +++ b/hacks/epicycle.man @@ -0,0 +1,204 @@ +.de EX \"Begin example +.ne 5 +.if n .sp 1 +.if t .sp .5 +.nf +.in +.5i +.. +.de EE +.fi +.in -.5i +.if n .sp 1 +.if t .sp .5 +.. +.TH XScreenSaver 1 "27-Apr-97" "X Version 11" +.SH NAME +epicycle - draws a point moving around a circle which moves around a cicle which... +.SH SYNOPSIS +.B epicycle +[\-display \fIhost:display.screen\fP] [\-root] [\-window] [\-mono] [\-install] [\-noinstall] [\-visual \fIviz\fP] [\-colors \fIN\fP] [\-foreground \fIname\fP] [\-color\-shift \fIN\fP] [\-delay \fImicroseconds\fP] [\-holdtime \fIseconds\fP] [\-linewidth \fIN\fP] [\-min_circles \fIN\fP] [\-max_circles \fIN\fP] [\-min_speed \fInumber\fP] [\-max_speed \fInumber\fP] [\-harmonics \fIN\fP] [\-timestep \fInumber\fP] [\-divisor_poisson \fIprobability\fP] [\-size_factor_min \fInumber\fP] [\-size_factor_max \fInumber\fP] +[\-fps] +.SH 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 complex, 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 generated, either with +command-line options or X resources. +.SH OPTIONS +.TP 8 +.B \-display \fIhost:display.screen\fP +Specifies which X display we should use (see the section DISPLAY NAMES in +.BR X (1) +for more information about this option). +.TP 8 +.B \-root +Draw on the root window. +.TP 8 +.B \-window +Draw on a newly-created window. This is the default. +.TP 8 +.B \-mono +If on a color display, pretend we're on a monochrome display. +If we're on a mono display, we have no choice. +.TP 8 +.B \-install +Install a private colormap for the window. +.TP 8 +.B \-noinstall +Don't install a private colormap for the window. +.TP 8 +.B \-visual \fIviz\fP +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 + +.RS +default, best, mono, monochrome, gray, grey, color, staticgray, staticcolor, +truecolor, grayscale, greyscale, pseudocolor, directcolor, \fInumber\fP + +If a decimal or hexadecimal number is used, +.BR XGetVisualInfo (3X) +is consulted to obtain the required visual. +.RE +.TP 8 +.B \-colors \fIN\fP +How many colors should be used (if possible). The colors are chosen +randomly. +.TP 8 +.B \-foreground \fIname\fP +With +.BR \-mono , +this option selects the foreground colour. +.TP 8 +.B \-delay \fImicroseconds\fP +Specifies the delay between drawing successive line segments of the +path. If you do not specify +.BR -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 +.B \-mono +is specified). +.TP 8 +.B \-holdtime \fIseconds\fP +When the figure is complete, +.I epicycle +pauses this number of seconds. +.TP 8 +.B \-linewidth \fIN\fP +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. +.TP 8 +.B \-min_circles \fIN\fP +Smallest number of epicycles in the figure. +.TP 8 +.B \-max_circles \fIN\fP +Largest number of epicycles in the figure. +.TP 8 +.B \-min_speed \fInumber\fP +Smallest possible value for the base speed of revolution of the +epicycles. The actual speeds of the epicycles vary from this down +to +.IB "min_speed / harmonics" . +.TP 8 +.B \-max_speed \fInumber\fP +Smallest possible value for the base speed of revolution of the +epicycles. +.TP 8 +.B \-harmonics \fIN\fP +Number of possible harmonics; the larger this value is, the greater +the possible variety of possible speeds of epicycle. +.TP 8 +.B \-timestep \fInumber\fP +Decreasing this value will reduce the distance the body moves for +each line segment, possibly producing a smoother figure. Increasing +it may produce faster results. +.TP 8 +.B \-divisor_poisson \fIprobability\fP +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 +.B \-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 +.B \-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. +.TP 8 +.B \-size_factor_min \fInumber\fP +Epicycles are always at least this factor smaller than their +parents. +.TP 8 +.B \-size_factor_max \fInumber\fP +Epicycles are never more than this factor smaller than their parents. +.TP 8 +.B \-fps +Display the current frame rate and CPU load. +.SH RESOURCES +.EX +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 +.EE +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 +.B \-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. +.SH 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. +.SH 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 heliocentric 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 heliocentric 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 +.I Principia Mathematica +was published in 1687, and proved that Kepler's laws derived from +Newtonian gravitation. +.SH 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. +.SH COPYRIGHT +Copyright \(co 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. +.SH AUTHOR +James Youngman <jay@gnu.org>, April 1998. |