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/* implements a classical perlin noise function */
/* https://en.wikipedia.org/wiki/Perlin_noise */
#include <assert.h>
#include <stdlib.h>
#include "din.h"
#include "v3f.h"
typedef struct din_t {
int width, height, depth;
unsigned seed;
int W_x_H;
v3f_t grid[];
} din_t;
/* return random number between -1 and +1 */
static inline float randf(unsigned *seed)
{
return 2.f / ((float)RAND_MAX) * rand_r(seed) - 1.f;
}
void din_randomize(din_t *din)
{
int x, y, z;
for (z = 0; z < din->depth; z++) {
for (y = 0; y < din->height; y++) {
for (x = 0; x < din->width; x++) {
v3f_t r;
r.x = randf(&din->seed);
r.y = randf(&din->seed);
r.z = randf(&din->seed);
din->grid[z * din->W_x_H + y * din->width + x] = v3f_normalize(&r);
}
}
}
}
din_t * din_new(int width, int height, int depth, unsigned seed)
{
din_t *din;
assert(width > 1);
assert(height > 1);
assert(depth > 1);
din = calloc(1, sizeof(din_t) + (sizeof(v3f_t) * (width * height * depth)));
if (!din)
return NULL;
din->width = width;
din->height = height;
din->depth = depth;
din->seed = seed;
/* premultiply this since we do it a lot in addressing din->grid[] */
din->W_x_H = width * height;
din_randomize(din);
return din;
}
void din_free(din_t *din)
{
free(din);
}
static inline float dotgradient(const din_t *din, int x, int y, int z, const v3f_t *coordinate)
{
v3f_t distance = v3f_sub(coordinate, &(v3f_t){.x = x, .y = y, .z = z});
return v3f_dot(&din->grid[z * din->W_x_H + y * din->width + x], &distance);
}
static inline float lerp(float a, float b, float t)
{
return (1.0f - t) * a + t * b;
}
static inline float smootherstep(float x) {
return x * x * x * (x * (x * 6.f - 15.f) + 10.f);
}
/* coordinate is in a unit cube of -1...+1 */
float din(din_t *din, v3f_t *coordinate)
{
int x0, y0, z0, x1, y1, z1;
float i1, i2, ii1, ii2;
float tx, ty, tz;
float n0, n1;
#if 0
assert(din);
assert(coordinate);
assert(coordinate->x >= -1.f && coordinate->x <= 1.f);
assert(coordinate->y >= -1.f && coordinate->y <= 1.f);
assert(coordinate->z >= -1.f && coordinate->z <= 1.f);
#endif
coordinate->x = .5f + (coordinate->x * .5f + .5f) * (float)(din->width - 2);
coordinate->y = .5f + (coordinate->y * .5f + .5f) * (float)(din->height - 2);
coordinate->z = .5f + (coordinate->z * .5f + .5f) * (float)(din->depth - 2);
x0 = floorf(coordinate->x);
y0 = floorf(coordinate->y);
z0 = floorf(coordinate->z);
x1 = x0 + 1;
y1 = y0 + 1;
z1 = z0 + 1;
tx = coordinate->x - (float)x0;
ty = coordinate->y - (float)y0;
tz = coordinate->z - (float)z0;
n0 = dotgradient(din, x0, y0, z0, coordinate);
n1 = dotgradient(din, x1, y0, z0, coordinate);
tx = smootherstep(tx);
i1 = lerp(n0, n1, tx);
n0 = dotgradient(din, x0, y1, z0, coordinate);
n1 = dotgradient(din, x1, y1, z0, coordinate);
i2 = lerp(n0, n1, tx);
ty = smootherstep(ty);
ii1 = lerp(i1, i2, ty);
n0 = dotgradient(din, x0, y0, z1, coordinate);
n1 = dotgradient(din, x1, y0, z1, coordinate);
i1 = lerp(n0, n1, tx);
n0 = dotgradient(din, x0, y1, z1, coordinate);
n1 = dotgradient(din, x1, y1, z1, coordinate);
i2 = lerp(n0, n1, tx);
ii2 = lerp(i1, i2, ty);
tz = smootherstep(tz);
return lerp(ii1, ii2, tz) * 1.1547005383792515290182975610039f;
}
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