Reformulate perlin into a struct
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perlin.cpp
145
perlin.cpp
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@ -31,126 +31,76 @@
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#include <limits>
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#define LERP(a,b,t) lerp::quintic (a, b, t)
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struct params {
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typedef size_t seed_t;
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unsigned octaves;
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double persistence;
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double frequency;
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seed_t seed;
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// Just a random generator [-1.0, 1.0]
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double
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generate (intmax_t x, intmax_t y) {
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intmax_t mixed = rotate_left (x, sizeof (x) * 4) | y;
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seed_t key = (seed_t)mixed ^ seed;
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return util::hash (key) / (double)std::numeric_limits<intmax_t>::max ();
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generate (intmax_t x, intmax_t y) const {
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intmax_t n = x + 257 * y;
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n = (n << 13U) ^ n ^ (intmax_t)seed;
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return (1.0 - ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0);
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}
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double
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smooth2d (intmax_t x, intmax_t y) {
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double corners = (generate(x - 1, y - 1) +
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generate(x + 1, y - 1) +
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generate(x - 1, y + 1) +
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generate(x + 1, y + 1)) / 16.0;
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double sides = (generate(x - 1, y ) +
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generate(x + 1, y ) +
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generate(x, y - 1) +
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generate(x, y + 1)) / 8.0;
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double center = generate(x, y ) / 4.0;
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return corners + sides + center;
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eval (double x, double y) const {
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intmax_t x_int = intmax_t (x);
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double x_fac = x - x_int;
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intmax_t y_int = intmax_t (y);
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double y_fac = y - y_int;
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// Generate the four corner values
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double p0 = generate (x_int, y_int);
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double p1 = generate (x_int + 1, y_int);
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double p2 = generate (x_int, y_int + 1);
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double p3 = generate (x_int + 1, y_int + 1);
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// Interpolate on one dimension, then the other.
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return LERP (LERP (p0, p1, x_fac),
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LERP (p2, p3, x_fac),
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y_fac);
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}
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double
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sample (double x, double y) const {
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double total = 0.0;
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for (size_t i = 0; i < octaves; ++i) {
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double f = frequency * powf (2.0, i);
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double amplitude = powf (persistence, i);
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total += eval (x * f, y * f) * amplitude;
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total = max (-1.0, min (1.0, total));
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}
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return (1.0 + total) / 2.0;
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}
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params ():
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octaves (16),
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persistence (0.7),
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octaves (3),
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persistence (0.5),
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frequency (25.0),
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seed (util::random<size_t> ())
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{ ; }
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};
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// Just a random generator [-1.0, 1.0]
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static float
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generate (intmax_t x, intmax_t y, size_t seed) {
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intmax_t n = x + 257 * y;
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n = (n << 13U) ^ n ^ seed;
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return (1.0 - ((n * (n * n * 15731 + 789221) + 1376312589) & 0x7fffffff) / 1073741824.0f);
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}
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static double
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smooth2d (intmax_t x, intmax_t y, size_t seed) {
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double corners = (generate(x - 1, y - 1, seed) +
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generate(x + 1, y - 1, seed) +
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generate(x - 1, y + 1, seed) +
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generate(x + 1, y + 1, seed)) / 16.0;
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double sides = (generate(x - 1, y, seed) +
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generate(x + 1, y, seed) +
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generate(x, y - 1, seed) +
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generate(x, y + 1, seed)) / 8.0;
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double center = generate(x, y, seed) / 4.0;
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return corners + sides + center;
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}
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static double
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curve (double t) {
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return t * t * (3.0 - 2.0 * t);
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}
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static double
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sample2d (double x, double y, size_t seed) {
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intmax_t x_int = intmax_t (x);
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double x_fac = x - x_int;
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intmax_t y_int = intmax_t (y);
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double y_fac = y - y_int;
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double p0 = smooth2d (x_int, y_int, seed);
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double p1 = smooth2d (x_int + 1, y_int, seed);
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double p2 = smooth2d (x_int, y_int + 1, seed);
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double p3 = smooth2d (x_int + 1, y_int + 1, seed);
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double i0 = lerp::cosine (p0, p1, curve (x_fac));
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double i1 = lerp::cosine (p2, p3, curve (x_fac));
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double value = lerp::cosine (i0, i1, curve (y_fac));
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return value;
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}
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static double
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sigmoid (double x) {
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return -1.0 + 2.0 / (1.0 + exp (-2.0 * x));
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}
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static double
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perlin2d (double x, double y, size_t seed) {
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size_t levels = 16;
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double persistence = 0.7;
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double total = 0.0;
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for (size_t i = 0; i < levels; ++i) {
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double frequency = powf (2.0, i);
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double amplitude = powf (persistence, i);
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total += sample2d (x * frequency, y * frequency, seed) * amplitude;
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}
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return sigmoid (1.0 + total);
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}
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void
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static void
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perlin2d (uint8_t *restrict pixels, size_t width, size_t height, const params& p) {
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for (size_t y = 0; y < height; ++y)
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for (size_t x = 0; x < width; ++x) {
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double p = perlin2d (x / 10.0, y / 10.0, (size_t)pixels);
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pixels[x + y * width] = p * std::numeric_limits<uint8_t>::max ();
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double v = p.sample (x / double (width), y / double (height)); /*perlin2d (x / double (width),
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y / double (height),
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(size_t)pixels);*/
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pixels[x + y * width] = v * std::numeric_limits<uint8_t>::max ();
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}
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}
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@ -159,4 +109,3 @@ void
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perlin2d (uint8_t *restrict pixels, size_t width, size_t height) {
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perlin2d (pixels, width, height, params ());
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}
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