r.surf.fractal.1grass man page

r.surf.fractal — Creates a fractal surface of a given fractal dimension.

Keywords

raster, surface, fractal

Synopsis

r.surf.fractal
r.surf.fractal --help
r.surf.fractal output=name [dimension=float] [number=integer] [--overwrite] [--help] [--verbose] [--quiet] [--ui]

Flags

--overwrite
Allow output files to overwrite existing files
--help
Print usage summary
--verbose
Verbose module output
--quiet
Quiet module output
--ui
Force launching GUI dialog

Parameters

output=name [required]
Name for output raster map
dimension=float
Fractal dimension of surface (2 < D < 3)
Default: 2.05
number=integer
Number of intermediate images to produce
Default: 0

Description

r.surf.fractal 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).

This module generates naturally looking synthetical elevation models (DEM).

Note

This module requires the FFTW library for computing Discrete Fourier Transforms.

Example

Generate surface using fractals in selected region, set color table and display with shade.

g.region -p raster=elevation
r.surf.fractal output=fractals
r.colors map=fractals color=byr
r.relief input=fractals output=fractals_shade
d.mon wx0
d.shade shade=fractals_shade color=fractals b=50

Artificial surface created with fractals
Compare results when using different fractal dimensions:

# D=2.0005
g.region -dp
r.surf.fractal out=dem_d2_0005 dim=2.0005
r.info -r dem_d2_0005
r.mapcalc "dem_d2_0005_final = 1.0 * dem_d2_0005 + abs(min(dem_d2_0005))"
r.colors dem_d2_0005_final color=terrain
r.slope.aspect dem_d2_0005_final aspect=dem_d2_0005_final_as
# D=2.90
r.surf.fractal out=dem_d2_90 dim=2.90
r.info -r dem_d2_90
r.mapcalc "dem_d2_90_final = 1.0 * dem_d2_90 + abs(min(dem_d2_90))"
r.colors dem_d2_90_final color=terrain
r.slope.aspect dem_d2_90_final aspect=dem_d2_90_final_as

Artificial DEMs created with fractals:
top: fractal dimension d=2.0005 (left: elevation map, right: aspect map)
top: fractal dimension d=2.90 (left: elevation map, right: aspect map)

References

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.

See Also

r.surf.contour, r.surf.idw, r.surf.gauss, r.surf.random, v.surf.idw, v.surf.rst

Author

Jo Wood, Midlands Regional Research Laboratory (ASSIST), University of Leicester

Last changed: $Date: 2015-07-20 10:49:51 +0200 (Mon, 20 Jul 2015) $

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