1Pamcrater User Manual(0)                              Pamcrater User Manual(0)
2
3
4

NAME

6       pamcrater - create cratered terrain by fractal forgery
7
8

EXAMPLES

10           $ pamcrater | pamshadedrelief | pamx
11
12           $ pamcrater -number=500000 -height=1000 -width=1000 >craters.pam
13
14
15

SYNOPSIS

17       pamcrater
18
19       [-number n]
20
21       [-height pixels]
22
23       [-width pixels]
24
25       [-randomseed=integer]
26
27       [-verbose]
28
29

DESCRIPTION

31       This program is part of Netpbm(1).
32
33       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
37       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
45       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
50       You can visualize the terrain map by generating a shaded  relief  image
51       of it with pamshadedrelief.
52
53       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
58       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
64                       /\                            /\
65                 _____/  \____________/\____________/  \_____
66
67       Larger craters should really use this profile,  including  the  central
68       peak, and totally obliterate the pre-existing terrain.
69
70       The maxval of the PAM image is always 65535.
71
72       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
76
77

OPTIONS

79       All options can be abbreviated to their shortest unique prefix.
80
81
82
83       -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
94
95       -height height
96              This  sets  the  height of the generated image to height pixels.
97              The default height is 256 pixels.
98
99
100       -width width
101              This sets the width of the generated image to width pixels.  The
102              default width is 256 pixels.
103
104
105       -randomseed=integer
106              This  is the seed for the random number generator that generates
107              the pixels.
108
109              Use this to ensure you get the same image  on  separate  invoca‐
110              tions.
111
112              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
116              This option was new in Netpbm 10.61 (December 2012).
117
118
119       -verbose
120              This causes pamcrater to issue additional messages about what it
121              is doing.
122
123              This option was new in Neptbm 10.69 (December 2014).
124
125
126
127
128

DESIGN NOTES

130       Real craters have two distinct morphologies.
131
132
133

SEE ALSO

135       pamshadedrelief(1), ppmrelief(1), pnmsmooth(1) pam(1),
136
137
138
139       [1]    Peitgen, H.-O., and Saupe,  D.  eds.,  The  Science  Of  Fractal
140              Images, New York: Springer Verlag, 1988.
141
142
143
144

AUTHOR

146       pgmcrater, from which this is derived, was written by John Walker:
147
148       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
157       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
162
163

HISTORY

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
174       (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
178       The original 1991 pgmcrater manual contains the following:
179
180
181   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

DOCUMENT SOURCE

195       This  manual  page was generated by the Netpbm tool 'makeman' from HTML
196       source.  The master documentation is at
197
198              http://netpbm.sourceforge.net/doc/pamcrater.html
199
200netpbm documentation           03 November 2014       Pamcrater User Manual(0)
Impressum