112 lines
2.9 KiB
C++
112 lines
2.9 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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#define LERP(a,b,t) lerp::quintic (a, b, t)
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// Just a random generator [-1.0, 1.0]
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double
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util::perlin::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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util::perlin::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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util::perlin::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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util::perlin::perlin ():
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octaves (3),
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frequency (25.0),
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persistence (0.5),
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seed (util::random<size_t> ())
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{ ; }
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util::perlin::perlin (unsigned _octaves,
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double _frequency,
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double _persistence,
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seed_t _seed):
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octaves (_octaves),
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frequency (_frequency),
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persistence (_persistence),
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seed (_seed)
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{ ; }
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void
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util::perlin2d (uint8_t *restrict pixels,
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size_t width,
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size_t height,
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const perlin &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 v = p.sample (x / double (width), y / double (height));
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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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