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MKFRACTALSRA

Section: C Library Functions (3)
Updated: 16 Mar 1998
Index

NAME

mkFractalSra - make fractal brownian motion noise

SYNTAX

#include <xite/fractal.h>

IBAND mkFractalSra( double D, int xpow,
int ypow, double mean, double cstdev,
double stdev );

DESCRIPTION

Generates fractional brownian motion noisebased on the fractal dimension D as input.The algorithm is known as "Successive Random Addition"The generated band will have horizontal size 2**xpow + 1and vertical size 2**ypow + 1.

D        - fractional dimension (between 2.0 and 3.0)
xpow     - horizontal size: 2**xpow + 1
ypow     - vertical size: 2**ypow + 1
mean     - mean pixel value for corners
cstdev   - standard deviation for corners
stdev    - initial standard deviation for the rest
            of the image

Note that meanfar from 128 combined with largestandard deviations will give a lot of over/under-flows,and a very poor result. cstdevshould be small to avoid"tilting" the whole image.

RETURN VALUE

The generated band

ERROR HANDLING

return (IBAND)0 in case of error:
Couldn't allocate memory
D not between 2.0 and 3.0
xpow or ypow below 1
mean outside 0.0 .. 255.0
negative cstdev or stdev

EXAMPLE

IBAND b;
b = mkFractalSra(2.5, 7, 8, 100.0, 5.0, 25.0)

REFERENCE

.I Fournier, A., Fussel, D., and Carpenter, L.

"Computer rendering of stochastic models",Commun. ACM 25, 6 (June 1982), 372-382.

AUTHOR

Hĺvard Iversen, BLAB, Ifi, UiO

MODIFYED BY

Tor Lřnnestad, BLAB, Ifi, UiO

ID

$Id: mkFractalSra.c,v 1.29 1997/03/07 12:51:50 svein Exp $

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