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| -seed num | Sets the seed for the random number generator to the integer num. The seed used to create each picture is displayed on standard output (unless suppressed with the -quiet option). Pictures generated with the same seed will be identical. If no -seed 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. |
| -stars fraction | Specifies the percentage of pixels, in tenths of a percent, that will appear as stars, either surrounding a planet or filling the entire frame if -night is specified. The default fraction is 100. |
| -xsize|-width width | Sets the width of the generated image to width 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 pixmap, make a square one with ppmforge, then use pnmcut to extract a portion of the shape and size you require. |
| -ysize|-height height | Sets the height of the generated image to height pixels. The default height is 256 pixels. If the height specified exceeds the width, the width will be increased to equal the height. |
All flags can be abbreviated to their shortest unique prefix.
BUGS
The algorithms require the output pixmap 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 pixmap if necessary.
You may have to reduce the FFT mesh size on machines with 16-bit integers and segmented pointer architectures.
SEE ALSO
pnmcut(1), pnmdepth(1), ppmdither(1), ppmquant(1), ppm(5)
"Random Fractal Forgeries" by Richard F. Voss, in Fundamental Algorithms for Computer Graphics by Earnshaw et al. Berlin: Springer-Verlag, 1985.
The Science Of Fractal Images, edited by H. O. Peitgen and D. Saupe. New York: Springer-Verlag, 1988.
AUTHOR
John Walker
Autodesk SA
Avenue des Champs-Montants 14b
CH-2074 MARIN
Suisse/Schweiz/Svizzera/Svizra/Switzerland
Usenet: kelvin@Autodesk.com
Fax: 038/33 88 15
Voice: 038/33 76 33
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.
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 that creates
three-dimensional landscapes as well as clouds and planets, plus five more modules that 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.
25 October 1991