From fc22b3d6507c6745911b9dfcc68f1e665ae13dbc Mon Sep 17 00:00:00 2001 From: Daniel Baumann Date: Mon, 15 Apr 2024 21:43:11 +0200 Subject: Adding upstream version 4.22.0. Signed-off-by: Daniel Baumann --- upstream/opensuse-leap-15-6/man1/ppmforge.1 | 384 ++++++++++++++++++++++++++++ 1 file changed, 384 insertions(+) create mode 100644 upstream/opensuse-leap-15-6/man1/ppmforge.1 (limited to 'upstream/opensuse-leap-15-6/man1/ppmforge.1') diff --git a/upstream/opensuse-leap-15-6/man1/ppmforge.1 b/upstream/opensuse-leap-15-6/man1/ppmforge.1 new file mode 100644 index 00000000..ceddfb6f --- /dev/null +++ b/upstream/opensuse-leap-15-6/man1/ppmforge.1 @@ -0,0 +1,384 @@ +\ +.\" This man page was generated by the Netpbm tool 'makeman' from HTML source. +.\" Do not hand-hack it! If you have bug fixes or improvements, please find +.\" the corresponding HTML page on the Netpbm website, generate a patch +.\" against that, and send it to the Netpbm maintainer. +.TH "Ppmforge User Manual" 0 "25 October 1991" "netpbm documentation" + +.SH NAME + +ppmforge - fractal forgeries of clouds, planets, and starry skies +.UN synopsis +.SH SYNOPSIS + +\fBppmforge\fP + +[\fB-clouds\fP] +[\fB-night\fP] +[\fB-dimension\fP \fIdimen\fP] +[\fB-hour\fP \fIhour\fP] +[\fB-inclination|-tilt\fP \fIangle\fP] +[\fB-mesh\fP \fIsize\fP] +[\fB-power\fP \fIfactor\fP] +[\fB-glaciers\fP \fIlevel\fP] +[\fB-ice\fP \fIlevel\fP] +[\fB-saturation\fP \fIsat\fP] +[\fB-seed\fP \fIseed\fP] +[\fB-stars\fP \fIfraction\fP] +[{\fB-xsize\fP|\fB-width\fP} \fIwidth\fP] +[{\fB-ysize\fP|\fB-height\fP} \fIheight\fP] + +.UN description +.SH DESCRIPTION +.PP +This program is part of +.BR "Netpbm" (1)\c +\&. +.PP +\fBppmforge\fP generates three kinds of ``random fractal forgeries,'' +the term coined by Richard F. Voss of the IBM Thomas J. Watson +Research Center for seemingly realistic pictures of natural objects +generated by simple algorithms embodying randomness and fractal +self-similarity. The techniques used by \fBppmforge\fP are +essentially those given by Voss[1], particularly the technique of +spectral synthesis explained in more detail by Dietmar Saupe[2]. +.PP +The program generates two varieties of pictures: planets and +clouds, which are just different renderings of data generated in an +identical manner, illustrating the unity of the fractal structure of +these very different objects. A third type of picture, a starry sky, +is synthesised directly from pseudorandom numbers. +.PP +The generation of planets or clouds begins with the preparation of +an array of random data in the frequency domain. The size of this +array, the ``mesh size,'' can be set with the \fB-mesh\fP option; the +larger the mesh the more realistic the pictures but the calculation +time and memory requirement increases as the square of the mesh size. +The fractal dimension, which you can specify with the +\fB-dimension\fP option, determines the roughness of the terrain on +the planet or the scale of detail in the clouds. As the fractal +dimension is increased, more high frequency components are added into +the random mesh. +.PP +Once the mesh is generated, an inverse two dimensional Fourier +transform is performed upon it. This converts the original random +frequency domain data into spatial amplitudes. We scale the real +components that result from the Fourier transform into numbers from 0 +to 1 associated with each point on the mesh. You can further modify +this number by applying a ``power law scale'' to it with the +\fB-power\fP option. Unity scale leaves the numbers unmodified; a +power scale of 0.5 takes the square root of the numbers in the mesh, +while a power scale of 3 replaces the numbers in the mesh with their +cubes. Power law scaling is best envisioned by thinking of the data +as representing the elevation of terrain; powers less than 1 yield +landscapes with vertical scarps that look like glacially-carved +valleys; powers greater than one make fairy-castle spires (which +require large mesh sizes and high resolution for best results). +.PP +After these calculations, we have a array of the specified size +containing numbers that range from 0 to 1. \fBppmforge\fP generates +as follows: +.PP +The randomness in the image is limited before Netpbm 10.37 (December +2006) -- if you run the program twice in the same second, you may get +identical output. + + +.TP +\fBClouds\fP +A color map is created that ranges from pure blue to white by +increasing admixture (desaturation) of blue with white. Numbers less +than 0.5 are colored blue, numbers between 0.5 and 1.0 are colored +with corresponding levels of white, with 1.0 being pure white. + +.TP +\fBPlanet\fP +The mesh is projected onto a sphere. Values less than 0.5 are treated +as water and values between 0.5 and 1.0 as land. The water areas are +colored based upon the water depth, and land based on its elevation. +The random depth data are used to create clouds over the oceans. An +atmosphere approximately like the Earth's is simulated; its light +absorption is calculated to create a blue cast around the limb of the +planet. A function that rises from 0 to 1 based on latitude is +modulated by the local elevation to generate polar ice caps--high +altitude terrain carries glaciers farther from the pole. Based on the +position of the star with respect to the observer, the apparent color +of each pixel of the planet is calculated by ray-tracing from the star +to the planet to the observer and applying a lighting model that sums +ambient light and diffuse reflection (for most planets ambient light +is zero, as their primary star is the only source of illumination). +Additional random data are used to generate stars around the planet. + +.TP +\fBNight\fP +A sequence of pseudorandom numbers is used to generate stars with a +user specified density. + +.PP +Cloud pictures always contain 256 or fewer colors and may be +displayed on most color mapped devices without further processing. +Planet pictures often contain tens of thousands of colors which must +be compressed with \fBpnmquant\fP or \fBppmdither\fP before encoding +in a color mapped format. If the display resolution is high enough, +\fBppmdither\fP generally produces better looking planets. +\fBpnmquant\fP tends to create discrete color bands, particularly in +the oceans, which are unrealistic and distracting. The number of +colors in starry sky pictures generated with the \fB-night\fP option +depends on the value specified for \fB-saturation\fP. Small values +limit the color temperature distribution of the stars and reduce the +number of colors in the image. If the \fB-saturation\fP is set to +0, none of the stars will be colored and the resulting image will +never contain more than 256 colors. Night sky pictures with many +different star colors often look best when color compressed by +\fBpamdepth\fP rather than \fBpnmquant\fP or \fBppmdither\fP. Try +\fInewmaxval\fP settings of 63, 31, or 15 with \fBpamdepth\fP to +reduce the number of colors in the picture to 256 or fewer. + + +.UN options +.SH OPTIONS +.PP +You can abbreviate any options to its shortest unique prefix. + + +.TP +\fB-clouds\fP +Generate clouds. An image of fractal clouds is generated. Selecting clouds +sets the default for fractal dimension to 2.15 and power scale factor +to 0.75. + +.TP +\fB-dimension\fP \fIdimen\fP + Sets the fractal dimension to the specified \fIdimen\fP, which +may be any floating point value between 0 and 3. Higher fractal +dimensions create more ``chaotic'' images, which require higher +resolution output and a larger FFT mesh size to look good. If no +dimension is specified, 2.4 is used when generating planets and 2.15 +for clouds. + +.TP +\fB-glaciers\fP \fIlevel\fP +The floating point \fIlevel\fP setting controls the extent to +which terrain elevation causes ice to appear at lower latitudes. The +default value of 0.75 makes the polar caps extend toward the equator +across high terrain and forms glaciers in the highest mountains, as on +Earth. Higher values make ice sheets that cover more and more of the +land surface, simulating planets in the midst of an ice age. Lower +values tend to be boring, resulting in unrealistic +geometrically-precise ice cap boundaries. + +.TP +\fB-hour\fP \fIhour\fP +When generating a planet, \fBppmforge\fP uses \fIhour\fP as the +"hour angle at the central meridian." If you specify \fB-hour +12\fP, for example, the planet will be fully illuminated, +corresponding to high noon at the longitude at the center of the +screen. You can specify any floating point value between 0 and 24 for +\fIhour\fP, but values which place most of the planet in darkness (0 +to 4 and 20 to 24) result in crescents which, while pretty, don't give +you many illuminated pixels for the amount of computing that's +required. If no \fB-hour\fP option is specified, a random hour angle +is chosen, biased so that only 25% of the images generated will be +crescents. + +.TP +\fB-ice\fP \fIlevel\fP +Sets the extent of the polar ice caps to the given floating point +\fIlevel\fP. The default level of 0.4 produces ice caps similar to +those of the Earth. Smaller values reduce the amount of ice, while +larger \fB-ice\fP settings create more prominent ice caps. +Sufficiently large values, such as 100 or more, in conjunction with +small settings for \fB-glaciers\fP (try 0.1) create "ice +balls" like Europa. + +.TP +\fB-inclination|-tilt\fP \fIangle\fP +The inclination angle of the planet with regard to its primary +star is set to \fIangle\fP, which can be any floating point value +from -90 to 90. The inclination angle can be thought of as +specifying, in degrees, the ``season'' the planet is presently +experiencing or, more precisely, the latitude at which the star +transits the zenith at local noon. If 0, the planet is at equinox; +the star is directly overhead at the equator. Positive values +represent summer in the northern hemisphere, negative values summer in +the southern hemisphere. The Earth's inclination angle, for example, +is about 23.5 at the June solstice, 0 at the equinoxes in March and +September, and -23.5 at the December solstice. If no inclination +angle is specified, a random value between -21.6 and 21.6 degrees is +chosen. + +.TP +\fB-mesh\fP \fIsize\fP +A mesh of \fIsize\fP by \fIsize\fP will be used for the fast +Fourier transform (FFT). Note that memory requirements and +computation speed increase as the square of \fIsize\fP; if you double +the mesh size, the program will use four times the memory and run four +times as long. The default mesh is 256x256, which produces reasonably +good looking pictures while using half a megabyte for the 256x256 +array of single precision complex numbers required by the FFT. On +machines with limited memory capacity, you may have to reduce the mesh +size to avoid running out of RAM. Increasing the mesh size produces +better looking pictures; the difference becomes particularly +noticeable when generating high resolution images with relatively high +fractal dimensions (between 2.2 and 3). + +.TP +\fB-night\fP +A starry sky is generated. The stars are created by the same +algorithm used for the stars that surround planet pictures, but the +output consists exclusively of stars. + +.TP +\fB-power\fP \fIfactor\fP +Sets the "power factor" used to scale elevations +synthesised from the FFT to \fIfactor\fP, which can be any floating +point number greater than zero. If no factor is specified a default +of 1.2 is used if a planet is being generated, or 0.75 if clouds are +selected by the \fB-clouds\fP option. The result of the FFT image +synthesis is an array of elevation values between 0 and 1. A +non-unity power factor exponentiates each of these elevations to the +specified power. For example, a power factor of 2 squares each value, +while a power factor of 0.5 replaces each with its square root. (Note +that exponentiating values between 0 and 1 yields values that remain +within that range.) Power factors less than 1 emphasise large-scale +elevation changes at the expense of small variations. Power factors +greater than 1 increase the roughness of the terrain and, like high +fractal dimensions, may require a larger FFT mesh size and/or higher +screen resolution to look good. + +.TP +\fB-saturation\fP \fIsat\fP +Controls the degree of color saturation of the stars that surround +planet pictures and fill starry skies created with the \fB-night\fP +option. The default value of 125 creates stars which resemble the sky +as seen by the human eye from Earth's surface. Stars are dim; only +the brightest activate the cones in the human retina, causing color to +be perceived. Higher values of \fIsat\fP approximate the appearance +of stars from Earth orbit, where better dark adaptation, absence of +skyglow, and the concentration of light from a given star onto a +smaller area of the retina thanks to the lack of atmospheric +turbulence enhances the perception of color. Values greater than 250 +create ``science fiction'' skies that, while pretty, don't occur in +this universe. +.sp +Thanks to the inverse square law combined with Nature's love of +mediocrity, there are many, many dim stars for every bright one. This +population relationship is accurately reflected in the skies created +by \fBppmforge\fP. Dim, low mass stars live much longer than bright +massive stars, consequently there are many reddish stars for every +blue giant. This relationship is preserved by \fBppmforge\fP. You +can reverse the proportion, simulating the sky as seen in a starburst +galaxy, by specifying a negative \fIsat\fP value. + +.TP +\fB-seed\fP \fInum\fP +Sets the seed for the random number generator to the integer +\fInum\fP. The seed used to create each picture is displayed on +standard output (unless suppressed with the \fB-quiet\fP option). +Pictures generated with the same seed will be identical. If no +\fB-seed\fP is specified, a random seed derived from the date and +time will be chosen. Specifying an explicit seed allows you to +re-render a picture you particularly like at a higher resolution or +with different viewing parameters. + +.TP +\fB-stars\fP \fIfraction\fP +Specifies the percentage of pixels, in tenths of a percent, which +will appear as stars, either surrounding a planet or filling the +entire frame if \fB-night\fP is specified. The default +\fIfraction\fP is 100. + +.TP +\fB-xsize|-width\fP\fI width\fP +Sets the width of the generated image to \fIwidth\fP pixels. The +default width is 256 pixels. Images must be at least as wide as they +are high; if a width less than the height is specified, it will be +increased to equal the height. If you must have a long skinny image, +make a square one with \fBppmforge\fP, then use \fBpamcut\fP to +extract a portion of the shape and size you require. + +.TP +\fB-ysize|-height\fP \fIheight\fP +Sets the height of the generated image to \fIheight\fP pixels. +The default height is 256 pixels. If the height specified exceeds the +width, the width will be increased to equal the height. + + + +.UN limitations +.SH LIMITATIONS +.PP +The algorithms require the output image to be at least as wide as +it is high, and the width to be an even number of pixels. These +constraints are enforced by increasing the size of the requested +image if necessary. +.PP +You may have to reduce the FFT mesh size on machines with 16 bit +integers and segmented pointer architectures. + +.UN seealso +.SH SEE ALSO +.BR "pamcut" (1)\c +\&, +.BR "pamdepth" (1)\c +\&, +.BR "ppmdither" (1)\c +\&, +.BR "pnmquant" (1)\c +\&, +.BR "ppm" (5)\c +\& + + +.TP +[1] +Voss, Richard F., ``Random Fractal Forgeries,'' in Earnshaw +et. al., Fundamental Algorithms for Computer Graphics, Berlin: +Springer-Verlag, 1985. + +.TP +[2] +Peitgen, H.-O., and Saupe, D. eds., The Science Of Fractal Images, +New York: Springer Verlag, 1988. + + + +.UN author +.SH AUTHOR + +.nf +John Walker +Autodesk SA +Avenue des Champs-Montants 14b +CH-2074 MARIN +Suisse/Schweiz/Svizzera/Svizra/Switzerland + \fBUsenet:\fP\fIkelvin@Autodesk.com\fP + \fBFax:\fP038/33 88 15 + \fBVoice:\fP038/33 76 33 +.fi +.PP +Permission to use, copy, modify, and distribute this software and its +documentation for any purpose and without fee is hereby granted, +without any conditions or restrictions. This software is provided ``as +is'' without express or implied warranty. + +.SS PLUGWARE! + +If you like this kind of stuff, you may also enjoy ``James Gleick's +Chaos--The Software'' for MS-DOS, available for $59.95 from your +local software store or directly from Autodesk, Inc., Attn: Science +Series, 2320 Marinship Way, Sausalito, CA 94965, USA. Telephone: +(800) 688-2344 toll-free or, outside the U.S. (415) 332-2344 Ext +4886. Fax: (415) 289-4718. ``Chaos--The Software'' includes a more +comprehensive fractal forgery generator which creates +three-dimensional landscapes as well as clouds and planets, plus five +more modules which explore other aspects of Chaos. The user guide of +more than 200 pages includes an introduction by James Gleick and +detailed explanations by Rudy Rucker of the mathematics and algorithms +used by each program. +.SH DOCUMENT SOURCE +This manual page was generated by the Netpbm tool 'makeman' from HTML +source. The master documentation is at +.IP +.B http://netpbm.sourceforge.net/doc/ppmforge.html +.PP \ No newline at end of file -- cgit v1.2.3