163 lines
4.4 KiB
C++
163 lines
4.4 KiB
C++
/*
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* This file is part of libgim.
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*
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* libgim is free software: you can redistribute it and/or modify it under the
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* terms of the GNU General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* libgim is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License
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* along with libgim. If not, see <http://www.gnu.org/licenses/>.
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*
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* Copyright 2011 Danny Robson <danny@nerdcruft.net>
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*/
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#include "perlin.hpp"
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#include "bitwise.hpp"
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#include "debug.hpp"
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#include "hash.hpp"
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#include "lerp.hpp"
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#include "maths.hpp"
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#include "random.hpp"
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#include <cmath>
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#include <limits>
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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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seed_t seed;
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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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}
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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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}
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params ():
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octaves (16),
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persistence (0.7),
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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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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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}
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}
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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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