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/*****************************************************************
Implementation of the fractional Brownian motion algorithm. These
functions were originally the work of F. Kenton Musgrave.
For documentation of the different functions please refer to the
book:
"Texturing and modeling: a procedural approach"
by David S. Ebert et. al.
******************************************************************/
#if defined (_MSC_VER)
#include <ntqglobal.h>
#endif
#include <time.h>
#include <stdlib.h>
#include "fbm.h"
#if defined(Q_CC_MSVC)
#pragma warning(disable:4244)
#endif
/* Definitions used by the noise2() functions */
#define B 0x100
#define BM 0xff
#define N 0x1000
#define NP 12 /* 2^N */
#define NM 0xfff
static int p[B + B + 2];
static float g3[B + B + 2][3];
static float g2[B + B + 2][2];
static float g1[B + B + 2];
static int start = 1;
static void init(void);
#define s_curve(t) ( t * t * (3. - 2. * t) )
#define lerp(t, a, b) ( a + t * (b - a) )
#define setup(i,b0,b1,r0,r1)\
t = vec[i] + N;\
b0 = ((int)t) & BM;\
b1 = (b0+1) & BM;\
r0 = t - (int)t;\
r1 = r0 - 1.;
#define at3(rx,ry,rz) ( rx * q[0] + ry * q[1] + rz * q[2] )
static float noise3(float vec[3]);
/* Fractional Brownian Motion function */
double fBm( Vector point, double H, double lacunarity, double octaves,
int init )
{
double value, frequency, remainder;
int i;
static double exponent_array[10];
float vec[3];
/* precompute and store spectral weights */
if ( init ) {
start = 1;
srand( time(0) );
/* seize required memory for exponent_array */
frequency = 1.0;
for (i=0; i<=octaves; i++) {
/* compute weight for each frequency */
exponent_array[i] = pow( frequency, -H );
frequency *= lacunarity;
}
}
value = 0.0; /* initialize vars to proper values */
frequency = 1.0;
vec[0]=point.x;
vec[1]=point.y;
vec[2]=point.z;
/* inner loop of spectral construction */
for (i=0; i<octaves; i++) {
/* value += noise3( vec ) * exponent_array[i];*/
value += noise3( vec ) * exponent_array[i];
vec[0] *= lacunarity;
vec[1] *= lacunarity;
vec[2] *= lacunarity;
} /* for */
remainder = octaves - (int)octaves;
if ( remainder ) /* add in ``octaves'' remainder */
/* ``i'' and spatial freq. are preset in loop above */
value += remainder * noise3( vec ) * exponent_array[i];
return( value );
} /* fBm() */
float noise3(float vec[3])
{
int bx0, bx1, by0, by1, bz0, bz1, b00, b10, b01, b11;
float rx0, rx1, ry0, ry1, rz0, rz1, *q, sy, sz, a, b, c, d, t, u, v;
int i, j;
if (start) {
start = 0;
init();
}
setup(0, bx0,bx1, rx0,rx1);
setup(1, by0,by1, ry0,ry1);
setup(2, bz0,bz1, rz0,rz1);
i = p[ bx0 ];
j = p[ bx1 ];
b00 = p[ i + by0 ];
b10 = p[ j + by0 ];
b01 = p[ i + by1 ];
b11 = p[ j + by1 ];
t = s_curve(rx0);
sy = s_curve(ry0);
sz = s_curve(rz0);
q = g3[ b00 + bz0 ] ; u = at3(rx0,ry0,rz0);
q = g3[ b10 + bz0 ] ; v = at3(rx1,ry0,rz0);
a = lerp(t, u, v);
q = g3[ b01 + bz0 ] ; u = at3(rx0,ry1,rz0);
q = g3[ b11 + bz0 ] ; v = at3(rx1,ry1,rz0);
b = lerp(t, u, v);
c = lerp(sy, a, b);
q = g3[ b00 + bz1 ] ; u = at3(rx0,ry0,rz1);
q = g3[ b10 + bz1 ] ; v = at3(rx1,ry0,rz1);
a = lerp(t, u, v);
q = g3[ b01 + bz1 ] ; u = at3(rx0,ry1,rz1);
q = g3[ b11 + bz1 ] ; v = at3(rx1,ry1,rz1);
b = lerp(t, u, v);
d = lerp(sy, a, b);
return lerp(sz, c, d);
}
static void normalize2(float v[2])
{
float s;
s = sqrt(v[0] * v[0] + v[1] * v[1]);
v[0] = v[0] / s;
v[1] = v[1] / s;
}
static void normalize3(float v[3])
{
float s;
s = sqrt(v[0] * v[0] + v[1] * v[1] + v[2] * v[2]);
v[0] = v[0] / s;
v[1] = v[1] / s;
v[2] = v[2] / s;
}
static void init(void)
{
int i, j, k;
for (i = 0 ; i < B ; i++) {
p[i] = i;
g1[i] = (float)((rand() % (B + B)) - B) / B;
for (j = 0 ; j < 2 ; j++)
g2[i][j] = (float)((rand() % (B + B)) - B) / B;
normalize2(g2[i]);
for (j = 0 ; j < 3 ; j++)
g3[i][j] = (float)((rand() % (B + B)) - B) / B;
normalize3(g3[i]);
}
while (--i) {
k = p[i];
p[i] = p[j = rand() % B];
p[j] = k;
}
for (i = 0 ; i < B + 2 ; i++) {
p[B + i] = p[i];
g1[B + i] = g1[i];
for (j = 0 ; j < 2 ; j++)
g2[B + i][j] = g2[i][j];
for (j = 0 ; j < 3 ; j++)
g3[B + i][j] = g3[i][j];
}
}
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