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noise.c
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#include "noise.h"
#include <math.h>
#include <stdio.h>
#include <immintrin.h>
static union { float d[4]; __m128 d4; } dUnion;
static union { int i[4]; __m128i i4; } iUnion;
static union { float t[4]; __m128 t4; } tUnion;
#ifdef INCLUDE_STACKTRACE
#define STARTFUNC(name) printf("s "); printf(name); printf("\n")
#define ENDFUNC(name) printf("r "); printf(name); printf("\n")
#else
#define STARTFUNC(name) ;
#define ENDFUNC(name) ;
#endif
// grad()
#if 0
static double indexedLerp(int idx, double d1, double d2, double d3)
{
// STARTFUNC("indexedLerp");
const double cEdgeX[] = { 1.0,-1.0, 1.0,-1.0, 1.0,-1.0, 1.0,-1.0,
0.0, 0.0, 0.0, 0.0, 1.0, 0.0,-1.0, 0.0 };
const double cEdgeY[] = { 1.0, 1.0,-1.0,-1.0, 0.0, 0.0, 0.0, 0.0,
1.0,-1.0, 1.0,-1.0, 1.0,-1.0, 1.0,-1.0 };
const double cEdgeZ[] = { 0.0, 0.0, 0.0, 0.0, 1.0, 1.0,-1.0,-1.0,
1.0, 1.0,-1.0,-1.0, 0.0, 1.0, 0.0,-1.0 };
idx &= 0xf;
// ENDFUNC("indexedLerp");
return cEdgeX[idx] * d1 + cEdgeY[idx] * d2 + cEdgeZ[idx] * d3;
}
#else
ATTR(hot, const)
static inline double indexedLerp(int idx, double a, double b, double c)
{
// STARTFUNC("indexedLerp");
// ENDFUNC("indexedLerp");
switch (idx & 0xf)
{
case 0: return a + b;
case 1: return -a + b;
case 2: return a - b;
case 3: return -a - b;
case 4: return a + c;
case 5: return -a + c;
case 6: return a - c;
case 7: return -a - c;
case 8: return b + c;
case 9: return -b + c;
case 10: return b - c;
case 11: return -b - c;
case 12: return a + b;
case 13: return -b + c;
case 14: return -a + b;
case 15: return -b - c;
}
UNREACHABLE();
return 0;
}
#endif
void perlinInit(PerlinNoise *noise, uint64_t *seed)
{
int i = 0;
//memset(noise, 0, sizeof(*noise));
noise->a = nextDouble(seed) * 256.0;
noise->b = nextDouble(seed) * 256.0;
noise->c = nextDouble(seed) * 256.0;
noise->amplitude = 1.0;
noise->lacunarity = 1.0;
uint8_t *idx = noise->d;
for (i = 0; i < 256; i++)
{
idx[i] = i;
}
for (i = 0; i < 256; i++)
{
int j = nextInt(seed, 256 - i) + i;
uint8_t n = idx[i];
idx[i] = idx[j];
idx[j] = n;
idx[i + 256] = idx[i];
}
}
void xPerlinInit(PerlinNoise *noise, Xoroshiro *xr)
{
int i = 0;
//memset(noise, 0, sizeof(*noise));
noise->a = xNextDouble(xr) * 256.0;
noise->b = xNextDouble(xr) * 256.0;
noise->c = xNextDouble(xr) * 256.0;
noise->amplitude = 1.0;
noise->lacunarity = 1.0;
uint8_t *idx = noise->d;
for (i = 0; i < 256; i++)
{
idx[i] = i;
}
for (i = 0; i < 256; i++)
{
int j = xNextInt(xr, 256 - i) + i;
uint8_t n = idx[i];
idx[i] = idx[j];
idx[j] = n;
idx[i + 256] = idx[i];
}
}
double samplePerlin(const PerlinNoise *noise, double d1, double d2, double d3,
double yamp, double ymin)
{
// STARTFUNC("samplePerlin");
d1 += noise->a;
d2 += noise->b;
d3 += noise->c;
const uint8_t *idx = noise->d;
int i1 = (int) floor(d1);
int i2 = (int) floor(d2);
int i3 = (int) floor(d3);
d1 -= i1;
d2 -= i2;
d3 -= i3;
double t1 = d1*d1*d1 * (d1 * (d1*6.0-15.0) + 10.0);
double t2 = d2*d2*d2 * (d2 * (d2*6.0-15.0) + 10.0);
double t3 = d3*d3*d3 * (d3 * (d3*6.0-15.0) + 10.0);
if (yamp)
{
double yclamp = ymin < d2 ? ymin : d2;
d2 -= floor(yclamp / yamp) * yamp;
}
i1 &= 0xff;
i2 &= 0xff;
i3 &= 0xff;
int a1 = idx[i1] + i2;
int b1 = idx[i1+1] + i2;
int a2 = idx[a1] + i3;
int a3 = idx[a1+1] + i3;
int b2 = idx[b1] + i3;
int b3 = idx[b1+1] + i3;
double l1 = indexedLerp(idx[a2], d1, d2, d3);
double l2 = indexedLerp(idx[b2], d1-1, d2, d3);
double l3 = indexedLerp(idx[a3], d1, d2-1, d3);
double l4 = indexedLerp(idx[b3], d1-1, d2-1, d3);
double l5 = indexedLerp(idx[a2+1], d1, d2, d3-1);
double l6 = indexedLerp(idx[b2+1], d1-1, d2, d3-1);
double l7 = indexedLerp(idx[a3+1], d1, d2-1, d3-1);
double l8 = indexedLerp(idx[b3+1], d1-1, d2-1, d3-1);
l1 = lerp(t1, l1, l2);
l3 = lerp(t1, l3, l4);
l5 = lerp(t1, l5, l6);
l7 = lerp(t1, l7, l8);
l1 = lerp(t2, l1, l3);
l5 = lerp(t2, l5, l7);
// ENDFUNC("samplePerlin");
return lerp(t3, l1, l5);
}
double samplePerlinSmallSIMD(const PerlinNoise *noise, double d1, double d2, double d3,
double yamp, double ymin)
{
d1 += noise->a;
d2 += noise->b;
d3 += noise->c;
const uint8_t *idx = noise->d;
int i1 = (int) floor(d1);
int i2 = (int) floor(d2);
int i3 = (int) floor(d3);
d1 -= i1;
d2 -= i2;
d3 -= i3;
double t1 = d1*d1*d1 * (d1 * (d1*6.0-15.0) + 10.0);
double t2 = d2*d2*d2 * (d2 * (d2*6.0-15.0) + 10.0);
double t3 = d3*d3*d3 * (d3 * (d3*6.0-15.0) + 10.0);
if (yamp)
{
double yclamp = ymin < d2 ? ymin : d2;
d2 -= floor(yclamp / yamp) * yamp;
}
i1 &= 0xff;
i2 &= 0xff;
i3 &= 0xff;
int a1 = idx[i1] + i2;
int b1 = idx[i1+1] + i2;
int a2 = idx[a1] + i3;
int a3 = idx[a1+1] + i3;
int b2 = idx[b1] + i3;
int b3 = idx[b1+1] + i3;
double l1 = indexedLerp(idx[a2], d1, d2, d3);
double l2 = indexedLerp(idx[b2], d1-1, d2, d3);
double l3 = indexedLerp(idx[a3], d1, d2-1, d3);
double l4 = indexedLerp(idx[b3], d1-1, d2-1, d3);
double l5 = indexedLerp(idx[a2+1], d1, d2, d3-1);
double l6 = indexedLerp(idx[b2+1], d1-1, d2, d3-1);
double l7 = indexedLerp(idx[a3+1], d1, d2-1, d3-1);
double l8 = indexedLerp(idx[b3+1], d1-1, d2-1, d3-1);
__m128 t1four = _mm_set1_ps(t1);
__m128 l2468 = _mm_setr_ps(l2, l4, l6, l8);
static union {float l[4]; __m128 l4;} l1357;
l1357.l4 = _mm_setr_ps(l1, l3, l5, l7);
l1357.l4 = _mm_add_ps(
l1357.l4,
_mm_mul_ps(
t1four,
_mm_sub_ps(l2468, l1357.l4)
)
);
l1 = lerp(t2, l1357.l[0], l1357.l[1]);
l5 = lerp(t2, l1357.l[2], l1357.l[3]);
return lerp(t3, l1, l5);
}
double samplePerlinSIMD(const PerlinNoise *noise, double d1, double d2, double d3, double yamp, double ymin)
{
dUnion.d4= _mm_add_ps(_mm_setr_ps(d1, d2, d3, 0), _mm_setr_ps(noise->a, noise->b, noise->c, 0));
iUnion.i4 = _mm_cvttps_epi32(_mm_floor_ps(dUnion.d4));
dUnion.d4 = _mm_sub_ps(dUnion.d4, _mm_cvtepi32_ps(iUnion.i4));
const uint8_t *idx = noise->d;
tUnion.t4 = _mm_mul_ps(
dUnion.d4,
_mm_mul_ps(
dUnion.d4,
_mm_mul_ps(
dUnion.d4,
_mm_add_ps(
_mm_mul_ps(
dUnion.d4,
_mm_sub_ps(
_mm_mul_ps(
dUnion.d4,
_mm_setr_ps(6, 6, 6, 0)
),
_mm_setr_ps(15, 15, 15, 0)
)
),
_mm_setr_ps(10, 10, 10, 0)
)
)
)
);
// i4 = _mm_and_epi32(i4,
__m128i fourtest = _mm_set1_epi32(0xff);
iUnion.i4 = _mm_and_si128(fourtest, iUnion.i4);
//int i1 = i4.m128i_i32[0];
int i1 = iUnion.i[0];
int i2 = iUnion.i[1];
int i3 = iUnion.i[2];
d1 = dUnion.d[0];
d2 = dUnion.d[1];
d3 = dUnion.d[2];
if (yamp)
{
double yclamp = ymin < d2 ? ymin : d2;
d2 -= floor(yclamp / yamp) * yamp;
}
int a1 = idx[i1] + i2;
int b1 = idx[i1 +1] + i2;
int a2 = idx[a1] + i3;
int a3 = idx[a1+1] + i3;
int b2 = idx[b1] + i3;
int b3 = idx[b1+1] + i3;
double l1 = indexedLerp(idx[a2], d1, d2, d3);
double l2 = indexedLerp(idx[b2], d1-1, d2, d3);
double l3 = indexedLerp(idx[a3], d1, d2-1, d3);
double l4 = indexedLerp(idx[b3], d1-1, d2-1, d3);
double l5 = indexedLerp(idx[a2+1], d1, d2, d3-1);
double l6 = indexedLerp(idx[b2+1], d1-1, d2, d3-1);
double l7 = indexedLerp(idx[a3+1], d1, d2-1, d3-1);
double l8 = indexedLerp(idx[b3+1], d1-1, d2-1, d3-1);
__m128 t1four = _mm_set1_ps(tUnion.t[0]);
__m128 t2four = _mm_setr_ps(tUnion.t[1], 0, tUnion.t[1], 0);
static union {float l[4]; __m128 l4;} l1357;
l1357.l4 = _mm_setr_ps(l1, l3, l5, l7);
__m128 l2468 = _mm_setr_ps(l2, l4, l6, l8);
l1357.l4 = _mm_add_ps(
l1357.l4,
_mm_mul_ps(
t1four,
_mm_sub_ps(l2468, l1357.l4)
)
);
__m128 l0307 = _mm_setr_ps(l1357.l[1], 0, l1357.l[3], 0);
static union {float l[4]; __m128 l4;} l1050;
l1050.l4 = _mm_setr_ps(l1357.l[0], 0, l1357.l[2], 0);
l1050.l4 = _mm_add_ps(
l1050.l4,
_mm_mul_ps(
t2four,
_mm_sub_ps(l0307, l1050.l4)
)
);
return lerp(tUnion.t[2], l1050.l[0], l1050.l[2]);
}
static
void samplePerlinBeta17Terrain(const PerlinNoise *noise, double *v,
double d1, double d3, double yLacAmp)
{
int genFlag = -1;
double l1 = 0;
double l3 = 0;
double l5 = 0;
double l7 = 0;
d1 += noise->a;
d3 += noise->c;
const uint8_t *idx = noise->d;
int i1 = (int) floor(d1);
int i3 = (int) floor(d3);
d1 -= i1;
d3 -= i3;
double t1 = d1*d1*d1 * (d1 * (d1*6.0-15.0) + 10.0);
double t3 = d3*d3*d3 * (d3 * (d3*6.0-15.0) + 10.0);
i1 &= 0xff;
i3 &= 0xff;
double d2;
int i2, yi, yic, gfCopy;
for (yi = 0; yi <= 7; yi++)
{
d2 = yi*noise->lacunarity*yLacAmp+noise->b;
i2 = ((int) floor(d2)) & 0xff;
if (yi == 0 || i2 != genFlag)
{
yic = yi;
gfCopy = genFlag;
genFlag = i2;
}
}
genFlag = gfCopy;
double t2;
for (yi = yic; yi <= 8; yi++)
{
d2 = yi*noise->lacunarity*yLacAmp+noise->b;
i2 = (int) floor(d2);
d2 -= i2;
t2 = d2*d2*d2 * (d2 * (d2*6.0-15.0) + 10.0);
i2 &= 0xff;
if (yi == 0 || i2 != genFlag)
{
genFlag = i2;
int a1 = idx[i1] + i2;
int b1 = idx[i1+1] + i2;
int a2 = idx[a1] + i3;
int a3 = idx[a1+1] + i3;
int b2 = idx[b1] + i3;
int b3 = idx[b1+1] + i3;
double m1 = indexedLerp(idx[a2], d1, d2, d3);
double l2 = indexedLerp(idx[b2], d1-1, d2, d3);
double m3 = indexedLerp(idx[a3], d1, d2-1, d3);
double l4 = indexedLerp(idx[b3], d1-1, d2-1, d3);
double m5 = indexedLerp(idx[a2+1], d1, d2, d3-1);
double l6 = indexedLerp(idx[b2+1], d1-1, d2, d3-1);
double m7 = indexedLerp(idx[a3+1], d1, d2-1, d3-1);
double l8 = indexedLerp(idx[b3+1], d1-1, d2-1, d3-1);
l1 = lerp(t1, m1, l2);
l3 = lerp(t1, m3, l4);
l5 = lerp(t1, m5, l6);
l7 = lerp(t1, m7, l8);
}
if (yi >= 7)
{
double n1 = lerp(t2, l1, l3);
double n5 = lerp(t2, l5, l7);
v[yi-7] += lerp(t3, n1, n5) * noise->amplitude;
}
}
}
static double simplexGrad(int idx, double x, double y, double z, double d)
{
double con = d - x*x - y*y - z*z;
if (con < 0)
return 0;
con *= con;
return con * con * indexedLerp(idx, x, y, z);
}
double sampleSimplex2D(const PerlinNoise *noise, double x, double y)
{
const double SKEW = 0.5 * (sqrt(3) - 1.0);
const double UNSKEW = (3.0 - sqrt(3)) / 6.0;
double hf = (x + y) * SKEW;
int hx = (int)floor(x + hf);
int hz = (int)floor(y + hf);
double mhxz = (hx + hz) * UNSKEW;
double x0 = x - (hx - mhxz);
double y0 = y - (hz - mhxz);
int offx = (x0 > y0);
int offz = !offx;
double x1 = x0 - offx + UNSKEW;
double y1 = y0 - offz + UNSKEW;
double x2 = x0 - 1.0 + 2.0 * UNSKEW;
double y2 = y0 - 1.0 + 2.0 * UNSKEW;
int gi0 = noise->d[0xff & (hz)];
int gi1 = noise->d[0xff & (hz + offz)];
int gi2 = noise->d[0xff & (hz + 1)];
gi0 = noise->d[0xff & (gi0 + hx)];
gi1 = noise->d[0xff & (gi1 + hx + offx)];
gi2 = noise->d[0xff & (gi2 + hx + 1)];
double t = 0;
t += simplexGrad(gi0 % 12, x0, y0, 0.0, 0.5);
t += simplexGrad(gi1 % 12, x1, y1, 0.0, 0.5);
t += simplexGrad(gi2 % 12, x2, y2, 0.0, 0.5);
return 70.0 * t;
}
void octaveInit(OctaveNoise *noise, uint64_t *seed, PerlinNoise *octaves,
int omin, int len)
{
int i;
int end = omin+len-1;
double persist = 1.0 / ((1LL << len) - 1.0);
double lacuna = pow(2.0, end);
if (len < 1 || end > 0)
{
printf("octavePerlinInit(): unsupported octave range\n");
return;
}
if (end == 0)
{
perlinInit(&octaves[0], seed);
octaves[0].amplitude = persist;
octaves[0].lacunarity = lacuna;
persist *= 2.0;
lacuna *= 0.5;
i = 1;
}
else
{
skipNextN(seed, -end*262);
i = 0;
}
for (; i < len; i++)
{
perlinInit(&octaves[i], seed);
octaves[i].amplitude = persist;
octaves[i].lacunarity = lacuna;
persist *= 2.0;
lacuna *= 0.5;
}
noise->octaves = octaves;
noise->octcnt = len;
}
void octaveInitBeta(OctaveNoise *noise, uint64_t *seed, PerlinNoise *octaves,
int octcnt, double lac, double lacMul, double persist, double persistMul)
{
int i;
for (i = 0; i < octcnt; i++)
{
perlinInit(&octaves[i], seed);
octaves[i].amplitude = persist;
octaves[i].lacunarity = lac;
persist *= persistMul;
lac *= lacMul;
}
noise->octaves = octaves;
noise->octcnt = octcnt;
}
int xOctaveInit(OctaveNoise *noise, Xoroshiro *xr, PerlinNoise *octaves,
const double *amplitudes, int omin, int len, int nmax)
{
static const uint64_t md5_octave_n[][2] = {
{0xb198de63a8012672, 0x7b84cad43ef7b5a8}, // md5 "octave_-12"
{0x0fd787bfbc403ec3, 0x74a4a31ca21b48b8}, // md5 "octave_-11"
{0x36d326eed40efeb2, 0x5be9ce18223c636a}, // md5 "octave_-10"
{0x082fe255f8be6631, 0x4e96119e22dedc81}, // md5 "octave_-9"
{0x0ef68ec68504005e, 0x48b6bf93a2789640}, // md5 "octave_-8"
{0xf11268128982754f, 0x257a1d670430b0aa}, // md5 "octave_-7"
{0xe51c98ce7d1de664, 0x5f9478a733040c45}, // md5 "octave_-6"
{0x6d7b49e7e429850a, 0x2e3063c622a24777}, // md5 "octave_-5"
{0xbd90d5377ba1b762, 0xc07317d419a7548d}, // md5 "octave_-4"
{0x53d39c6752dac858, 0xbcd1c5a80ab65b3e}, // md5 "octave_-3"
{0xb4a24d7a84e7677b, 0x023ff9668e89b5c4}, // md5 "octave_-2"
{0xdffa22b534c5f608, 0xb9b67517d3665ca9}, // md5 "octave_-1"
{0xd50708086cef4d7c, 0x6e1651ecc7f43309}, // md5 "octave_0"
};
static const double lacuna_ini[] = { // -omin = 3..12
1, .5, .25, 1./8, 1./16, 1./32, 1./64, 1./128, 1./256, 1./512, 1./1024,
1./2048, 1./4096,
};
static const double persist_ini[] = { // len = 4..9
0, 1, 2./3, 4./7, 8./15, 16./31, 32./63, 64./127, 128./255, 256./511,
};
#if DEBUG
if (-omin < 0 || -omin >= (int) (sizeof(lacuna_ini)/sizeof(double)) ||
len < 0 || len >= (int) (sizeof(persist_ini)/sizeof(double)))
{
printf("Fatal: octave initialization out of range\n");
exit(1);
}
#endif
double lacuna = lacuna_ini[-omin];
double persist = persist_ini[len];
uint64_t xlo = xNextLong(xr);
uint64_t xhi = xNextLong(xr);
int i = 0, n = 0;
for (; i < len && n != nmax; i++, lacuna *= 2.0, persist *= 0.5)
{
if (amplitudes[i] == 0)
continue;
Xoroshiro pxr;
pxr.lo = xlo ^ md5_octave_n[12 + omin + i][0];
pxr.hi = xhi ^ md5_octave_n[12 + omin + i][1];
xPerlinInit(&octaves[n], &pxr);
octaves[n].amplitude = amplitudes[i] * persist;
octaves[n].lacunarity = lacuna;
n++;
}
noise->octaves = octaves;
noise->octcnt = n;
return n;
}
double sampleOctaveAmp(const OctaveNoise *noise, double x, double y, double z,
double yamp, double ymin, int ydefault)
{
double v = 0;
int i;
for (i = 0; i < noise->octcnt; i++)
{
PerlinNoise *p = noise->octaves + i;
double lf = p->lacunarity;
double ax = maintainPrecision(x * lf);
double ay = ydefault ? -p->b : maintainPrecision(y * lf);
double az = maintainPrecision(z * lf);
double pv = samplePerlin(p, ax, ay, az, yamp * lf, ymin * lf);
v += p->amplitude * pv;
}
return v;
}
double sampleOctave(const OctaveNoise *noise, double x, double y, double z)
{
STARTFUNC("sampleOctave");
double v = 0;
int i;
for (i = 0; i < noise->octcnt; i++)
{
//printf("oct: %d\n", noise->octcnt);
PerlinNoise *p = noise->octaves + i;
double lf = p->lacunarity;
double ax = maintainPrecision(x * lf);
double ay = maintainPrecision(y * lf);
double az = maintainPrecision(z * lf);
double pv = samplePerlinSmallSIMD(p, ax, ay, az, 0, 0);
//printf("%f\n", pv);
v += p->amplitude * pv;
}
ENDFUNC("sampleOctave");
return v;
}
double sampleOctaveBeta17Biome(const OctaveNoise *noise, double x, double z)
{
double v = 0;
int i;
for (i = 0; i < noise->octcnt; i++)
{
PerlinNoise *p = noise->octaves + i;
double lf = p->lacunarity;
double ax = maintainPrecision(x * lf) + p->a;
double az = maintainPrecision(z * lf) + p->b;
double pv = sampleSimplex2D(p, ax, az);
v += p->amplitude * pv;
}
return v;
}
void sampleOctaveBeta17Terrain(const OctaveNoise *noise, double *v,
double x, double z, int yLacFlag, double lacmin)
{
v[0] = 0.0;
v[1] = 0.0;
int i;
for (i = 0; i < noise->octcnt; i++)
{
PerlinNoise *p = noise->octaves + i;
double lf = p->lacunarity;
if (lacmin && lf > lacmin)
continue;
double ax = maintainPrecision(x * lf);
double az = maintainPrecision(z * lf);
samplePerlinBeta17Terrain(p, v, ax, az, yLacFlag ? 0.5 : 1.0);
}
}
void doublePerlinInit(DoublePerlinNoise *noise, uint64_t *seed,
PerlinNoise *octavesA, PerlinNoise *octavesB, int omin, int len)
{ // require: len >= 1 && omin+len <= 0
noise->amplitude = (10.0 / 6.0) * len / (len + 1);
octaveInit(&noise->octA, seed, octavesA, omin, len);
octaveInit(&noise->octB, seed, octavesB, omin, len);
}
/**
* Sets up a DoublePerlinNoise generator (MC 1.18+).
* @noise: Object to be initialized
* @xr: Xoroshiro random object
* @octaves: Octaves buffer, size has to be 2x (# non-zeros in amplitudes)
* @amplitudes: Octave amplitude, needs at least one non-zero
* @omin: First octave
* @len: Length of amplitudes array
* @nmax: Number of octaves available in buffer (can be <=0 to ignore)
* @return Number of octaves used (see octaves buffer size).
*/
int xDoublePerlinInit(DoublePerlinNoise *noise, Xoroshiro *xr,
PerlinNoise *octaves, const double *amplitudes, int omin, int len, int nmax)
{
int i, n = 0, na = -1, nb = -1;
if (nmax > 0)
{
na = (nmax + 1) >> 1;
nb = nmax - na;
}
n += xOctaveInit(&noise->octA, xr, octaves+n, amplitudes, omin, len, na);
n += xOctaveInit(&noise->octB, xr, octaves+n, amplitudes, omin, len, nb);
// trim amplitudes of zero
for (i = len-1; i >= 0 && amplitudes[i] == 0.0; i--)
len--;
for (i = 0; amplitudes[i] == 0.0; i++)
len--;
static const double amp_ini[] = { // (5 ./ 3) * len / (len + 1), len = 2..9
0, 5./6, 10./9, 15./12, 20./15, 25./18, 30./21, 35./24, 40./27, 45./30,
};
noise->amplitude = amp_ini[len];
return n;
}
double sampleDoublePerlin(const DoublePerlinNoise *noise,
double x, double y, double z)
{
STARTFUNC("sampleDoublePerlin");
const double f = 337.0 / 331.0;
double v = 0;
v += sampleOctave(&noise->octA, x, y, z);
v += sampleOctave(&noise->octB, x*f, y*f, z*f);
ENDFUNC("sampleDoublePerlin");
return v * noise->amplitude;
}