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