94 lines
1.8 KiB
C++
94 lines
1.8 KiB
C++
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#include <math.h>
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#include <stdint.h>
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#include "noise.h"
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#include "util.h"
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// C++ conversion of Ken Perlin's improved noise generator from
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// https://mrl.nyu.edu/~perlin/noise/
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static double
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grad(int hash, double x, double y, double z)
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{
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int h = hash & 15;
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double u = h < 8 ? x : y;
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double v = h < 4 ? y : h == 12 || h == 14 ? x : z;
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return ((h & 1) == 0 ? u : -u) + ((h & 2) == 0 ? v : -v);
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}
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static double
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lerp(double t, double a, double b)
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{
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return a + t * (b - a);
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}
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static double
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fade(double t)
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{
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return t * t * t * (t * (t * 6 - 15) + 10);
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}
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NoiseGenerator::NoiseGenerator()
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{
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// Generate a random permutation of 256 values from 0 to 255
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// inclusive. This is generated by setting each value in the
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// array to its index value, then putting it through a
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// Fisher-Yates shuffle.
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for (int i = 0; i < 256; i++) {
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perm[i] = i;
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}
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for (int i = 255; i > 0; i--) {
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int j = random() % (i + 1);
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swap_u8(perm[i], perm[j]);
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}
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for (int i = 0; i < 256; i++) {
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p[i] = perm[i];
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p[i+256] = perm[i];
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}
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}
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double
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NoiseGenerator::sample(double x, double y, double z)
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{
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uint16_t ux = (uint16_t)floor(x) & 255;
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uint16_t uy = (uint16_t)floor(y) & 255;
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uint16_t uz = (uint16_t)floor(z) & 255;
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double u, v, w;
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uint16_t a, aa, ab, b, ba, bb;
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x -= floor(x);
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u = fade(x);
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y -= floor(y);
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v = fade(y);
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z -= floor(z);
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w = fade(z);
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a = p[ux] + uy;
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aa = p[a] + uz;
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ab = p[a + 1] + uz;
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b = p[ux + 1] + uy;
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ba = p[b] + uz;
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bb = p[b + 1] + uz;
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return lerp(w, lerp(v, lerp(u, grad(p[aa], x, y, z),
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grad(p[ba], x-1, y, z)),
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lerp(u, grad(p[ab], x, y-1, z),
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grad(p[bb], x-1, y-1, z))),
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lerp(v, lerp(u, grad(p[aa+1], x, y, z-1),
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grad(p[ba+1], x-1, y, z-1)),
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lerp(u, grad(p[ab+1], x, y-1, z-1),
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grad(p[bb+1], x-1, y-1, z-1))));
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}
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