# Projects

## Noise

```/* coherent noise function over 1, 2 or 3 dimensions */

#include <stdlib.h>
#include <stdio.h>
#include <math.h>

#define B 0x100
#define BM 0xff

#define N 0x1000
#define NP 12   /* 2^N */
#define NM 0xfff

static 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 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.;

double noise1(double arg)
{
int bx0, bx1;
float rx0, rx1, sx, t, u, v, vec[1];

vec[0] = arg;
if (start) {
start = 0;
init();
}

setup(0, bx0,bx1, rx0,rx1);

sx = s_curve(rx0);

u = rx0 * g1[ p[ bx0 ] ];
v = rx1 * g1[ p[ bx1 ] ];

return lerp(sx, u, v);
}

float noise2(float vec[2])
{
int bx0, bx1, by0, by1, b00, b10, b01, b11;
float rx0, rx1, ry0, ry1, *q, sx, sy, a, b, t, u, v;
register i, j;

if (start) {
start = 0;
init();
}

setup(0, bx0,bx1, rx0,rx1);
setup(1, by0,by1, ry0,ry1);

i = p[ bx0 ];
j = p[ bx1 ];

b00 = p[ i + by0 ];
b10 = p[ j + by0 ];
b01 = p[ i + by1 ];
b11 = p[ j + by1 ];

sx = s_curve(rx0);
sy = s_curve(ry0);

#define at2(rx,ry) ( rx * q[0] + ry * q[1] )

q = g2[ b00 ] ; u = at2(rx0,ry0);
q = g2[ b10 ] ; v = at2(rx1,ry0);
a = lerp(sx, u, v);

q = g2[ b01 ] ; u = at2(rx0,ry1);
q = g2[ b11 ] ; v = at2(rx1,ry1);
b = lerp(sx, u, v);

return lerp(sy, a, b);
}

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;
register 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);

#define at3(rx,ry,rz) ( rx * q[0] + ry * q[1] + rz * q[2] )

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)((random() % (B + B)) - B) / B;

for (j = 0 ; j < 2 ; j++)
g2[i][j] = (float)((random() % (B + B)) - B) / B;
normalize2(g2[i]);

for (j = 0 ; j < 3 ; j++)
g3[i][j] = (float)((random() % (B + B)) - B) / B;
normalize3(g3[i]);
}

while (--i) {
k = p[i];
p[i] = p[j = random() % 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];
}
}
```