.TH r.surf.fractal 1grass "" "GRASS 6.4.4" "Grass User's Manual"
.SH NAME
\fI\fBr.surf.fractal\fR\fR  - Creates a fractal surface of a given fractal dimension.
.SH KEYWORDS
raster
.SH SYNOPSIS
\fBr.surf.fractal\fR
.br
\fBr.surf.fractal help\fR
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\fBr.surf.fractal output\fR=\fIstring\fR  [\fBdimension\fR=\fIfloat\fR]   [\fBnumber\fR=\fIinteger\fR]   [\-\-\fBverbose\fR]  [\-\-\fBquiet\fR] 
.SS Parameters:
.IP "\fBoutput\fR=\fIstring\fR" 4m
.br
Name for output raster map
.IP "\fBdimension\fR=\fIfloat\fR" 4m
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Fractal dimension of surface (2 < D < 3)
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Default: \fI2.05\fR
.IP "\fBnumber\fR=\fIinteger\fR" 4m
.br
Number of intermediate images to produce
.br
Default: \fI0\fR
.PP
.SH DESCRIPTION
\fBr.surf.fractal\fR creates a fractal surface of a given fractal
dimension. It uses the spectral synthesis method. The module can create
intermediate layers showing the build up of different spectral coefficients
(see Saupe, pp.106-107 for an example of this).
.PP
Use this module to generate naturally looking synthetical elevation models
(DEM).
.SH NOTE
This module requires the FFTW library
for computing Discrete Fourier Transforms.
.SH EXAMPLE
\fC
.DS
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# D=2.0005
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g.region \-dp
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r.surf.fractal out=dem_d2_0005 dim=2.0005
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r.info \-r dem_d2_0005
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r.mapcalc "dem_d2_0005_final = 1.0 * dem_d2_0005 + abs(min(dem_d2_0005))"
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r.colors dem_d2_0005_final color=terrain
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r.slope.aspect dem_d2_0005_final aspect=dem_d2_0005_final_as
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# D=2.90
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r.surf.fractal out=dem_d2_90 dim=2.90
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r.info \-r dem_d2_90
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r.mapcalc "dem_d2_90_final = 1.0 * dem_d2_90 + abs(min(dem_d2_90))"
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r.colors dem_d2_90_final color=terrain
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r.slope.aspect dem_d2_90_final aspect=dem_d2_90_final_as
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d.mon x0
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d.erase \-f
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d.split.frame
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d.frame \-s uno
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d.rast dem_d2_0005_final
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d.frame \-s dos
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d.rast dem_d2_0005_final_as
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d.frame \-s tres
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d.rast dem_d2_90_final
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d.frame \-s cuatro
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d.rast dem_d2_90_final_as
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.DE
\fR
Artificial DEMs created with fractals:
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top: fractal dimension d=2.0005 (left: elevation map, right: aspect map)
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top: fractal dimension d=2.90 (left: elevation map, right: aspect map)
.SH REFERENCE
Saupe, D. (1988) Algorithms for random fractals, in Barnsley M., 
Devaney R., Mandelbrot B., Peitgen, H-O., Saupe D., and Voss R.
(1988) The Science of Fractal Images, Ch. 2, pp.71-136. London:
Springer-Verlag.
.SH SEE ALSO
\fIr.surf.contour\fR,
\fIr.surf.idw\fR,
\fIr.surf.gauss\fR,
\fIr.surf.random\fR,
\fIr.surf.idw2\fR,
\fIv.surf.idw\fR,
\fIv.surf.rst\fR
.SH AUTHOR
Jo Wood,
Midlands Regional Research Laboratory (ASSIST),
University of Leicester
.PP
\fILast changed: $Date: 2012-11-27 01:18:53 +0100 (Tue, 27 Nov 2012) $\fR
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© 2003-2014 GRASS Development Team