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#include "common.hpp"
#include <cmath>
namespace procgen {
void prng_t::seed(uint32_t seed)
{
state = seed;
next();
next();
}
uint32_t prng_t::next(void)
{
// glibc's LCG parameters (with m = 2^32 - 1).
state *= 1103515245;
state += 12345;
return state;
}
float prng_t::next_float(void)
{
return (float)next() / 4294967295.0f;
}
void prng_t::unit_vec(float out[2])
{
float t;
t = next_float() * 2.0f * M_PI;
out[0] = cos(t);
out[1] = sin(t);
}
void perlin_noise_t::generate(prng_t *prng, size_t size_)
{
if (table)
delete table;
size = size_;
table = new float[size * size][2];
for (size_t y = 0; y < size; y++)
for (size_t x = 0; x < size; x++)
prng->unit_vec(table[y * size + x]);
}
float perlin_noise_t::table_dot(size_t nx, size_t ny, float dx, float dy)
{
return table[ny * size + nx][0] * dx + table[ny * size + nx][1] * dy;
}
static float smooth_step(float x)
{
return 3 * x * x - 2 * x * x * x;
}
float perlin_noise_t::get(float x, float y, float scale)
{
size_t nx, ny, nx1, ny1;
float s, t, a, b, c, d;
x /= scale;
y /= scale;
nx = (ssize_t)floor(x) & (size - 1);
ny = (ssize_t)floor(y) & (size - 1);
nx1 = (nx == size - 1 ? 0 : nx + 1);
ny1 = (ny == size - 1 ? 0 : ny + 1);
s = smooth_step(x - floor(x));
t = smooth_step(y - floor(y));
a = table_dot(nx, ny, -s, -t);
b = table_dot(nx1, ny, -s + 1.0f, -t);
c = table_dot(nx, ny1, -s, -t + 1.0f);
d = table_dot(nx1, ny1, -s + 1.0f, -t + 1.0f);
return bilerp(a, b, c, d, s, t);
}
perlin_noise_t::~perlin_noise_t()
{
delete table;
}
} // namespace procgen
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