1Pamcrater User Manual(0) Pamcrater User Manual(0)
2
6 pamcrater - create cratered terrain by fractal forgery
7
10 $ pamcrater | pamshadedrelief | pamx
11 $ pamcrater -number=500000 -height=1000 -width=1000 >craters.pam
13
17 pamcrater
18 [-number n]
20 [-height pixels]
22 [-width pixels]
24 [-randomseed=integer]
26 [-verbose]
28
31 This program is part of Netpbm(1).
32 pamcrater creates a PAM image which is a terrain map (not a visual
34 image) of cratered terrain. The terrain is as if a given number of
35 impacts into a surface create craters with random position and size.
36 The size distribution of the craters is based on a power law which
38 results in many more small craters than large ones. The number of
39 craters of a given size varies as the reciprocal of the area as
40 described on pages 31 and 32 of Peitgen and Saupe[1]; cratered bodies
41 in the Solar System are observed to obey this relationship. The for‐
42 mula used to obtain crater radii governed by this law from a uniformly
43 distributed pseudorandom sequence was developed by Rudy Rucker.
44 A terrain map is a two dimensional map of terrain elevations. the PAM
46 image that pamcrater produces is therefore not a visual image but a
47 depth-one image of tuple type "elevation", with the sample value being
48 proportional to an elevation.
49 You can visualize the terrain map by generating a shaded relief image
51 of it with pamshadedrelief.
52 High resolution images with large numbers of craters often benefit from
54 being piped through pnmsmooth. The averaging performed by this process
55 eliminates some of the jagged pixels and lends a mellow ``telescopic
56 image'' feel to the overall picture.
57 pamcrater generates only small craters, which are hemispherical in
59 shape (regardless of the incidence angle of the impacting body, as long
60 as the velocity is sufficiently high). Large craters, such as Coperni‐
61 cus and Tycho on the Moon, have a ``walled plain'' shape with a cross-
62 section more like:
63 /\ /\
65 _____/ \____________/\____________/ \_____
66 Larger craters should really use this profile, including the central
68 peak, and totally obliterate the pre-existing terrain.
69 The maxval of the PAM image is always 65535.
71 The randomness in the image is limited before Netpbm 10.37 (December
73 2006) -- if you run the program twice in the same second, you may get
74 identical output.
75
79 All options can be abbreviated to their shortest unique prefix.
80 -number n
84 This causes pamcrater to generate n craters. If you do not
85 specify -number, it generates 50000 craters. Don't expect to
86 see them all! For every large crater there are many, many more
87 tiny ones which tend simply to erode the landscape. In general,
88 the more craters you specify, the more realistic the result;
89 ideally you want the entire terrain to have been extensively
90 turned over again and again by cratering. High resolution
91 images containing five to ten million craters are stunning but
92 take longer to create.
93 -height height
96 This sets the height of the generated image to height pixels.
97 The default height is 256 pixels.
98 -width width
101 This sets the width of the generated image to width pixels. The
102 default width is 256 pixels.
103 -randomseed=integer
106 This is the seed for the random number generator that generates
107 the pixels.
108 Use this to ensure you get the same image on separate invoca‐
110 tions.
111 By default, pamcrater uses a seed derived from the time of day
113 and process ID, which gives you fairly uncorrelated results in
114 multiple invocations.
115 This option was new in Netpbm 10.61 (December 2012).
117 -verbose
120 This causes pamcrater to issue additional messages about what it
121 is doing.
122 This option was new in Neptbm 10.69 (December 2014).
124
130 Real craters have two distinct morphologies.
131
135 pamshadedrelief(1), ppmrelief(1), pnmsmooth(1) pam(1),
136 [1] Peitgen, H.-O., and Saupe, D. eds., The Science Of Fractal
140 Images, New York: Springer Verlag, 1988.
141
146 pgmcrater, from which this is derived, was written by John Walker:
147 John Walker
149 Autodesk SA
150 Avenue des Champs-Montants 14b
151 CH-2074 MARIN
152 Suisse/Schweiz/Svizzera/Svizra/Switzerland
153 Usenet:kelvin@Autodesk.com
154 Fax:038/33 88 15
155 Voice:038/33 76 33
156 Permission to use, copy, modify, and distribute this software and its
158 documentation for any purpose and without fee is hereby granted, with‐
159 out any conditions or restrictions. This software is provided "as is"
160 without express or implied warranty.
161
165 John Walker wrote pgmcrater in 1991 and it was included in Pbmplus.
166 pgmcrater did the equivalent of pamcrater | pamshadedrelief. In Netpbm
167 10.68 (September 2014), Bryan Henderson split the functions of pgm‐
168 crater into two programs, one (pamcrater) to compute elevations, and
169 the other (pamshadedrelief) to generate a shaded relief visual image
170 showing those elevations. Bryan did this because it is more in keeping
171 with Netpbm's modular architecture, and because the pamshadedrelief
172 might be useful with other inputs.
173 (Like all Netpbm programs, pgmcrater was not static between the two
175 events described above; minor changes, including replacement of most of
176 the code, happened in between).
177 The original 1991 pgmcrater manual contains the following:
179 PLUGWARE!
182 If you like this kind of stuff, you may also enjoy "James Gleick's
183 Chaos--The Software" for MS-DOS, available for $59.95 from your local
184 software store or directly from Autodesk, Inc., Attn: Science Series,
185 2320 Marinship Way, Sausalito, CA 94965, USA. Telephone: (800)
186 688-2344 toll-free or, outside the U.S. (415) 332-2344 Ext 4886. Fax:
187 (415) 289-4718. "Chaos--The Software" includes a more comprehensive
188 fractal forgery generator which creates three-dimensional landscapes as
189 well as clouds and planets, plus five more modules which explore other
190 aspects of Chaos. The user guide of more than 200 pages includes an
191 introduction by James Gleick and detailed explanations by Rudy Rucker
192 of the mathematics and algorithms used by each program.
193
195 This manual page was generated by the Netpbm tool 'makeman' from HTML
196 source. The master documentation is at
197 http://netpbm.sourceforge.net/doc/pamcrater.html
199netpbm documentation 03 November 2014 Pamcrater User Manual(0)