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/*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License along
* with FFmpeg; if not, write to the Free Software Foundation, Inc.,
* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
/**
* @file
* Perlin Noise generator, based on code from:
* https://adrianb.io/2014/08/09/perlinnoise.html
*
* Original article from Ken Perlin:
* http://mrl.nyu.edu/~perlin/paper445.pdf
*/
#include <math.h>
#include "libavutil/lfg.h"
#include "libavutil/random_seed.h"
#include "perlin.h"
static inline int inc(int num, int period)
{
num++;
if (period > 0)
num %= period;
return num;
}
static inline double grad(int hash, double x, double y, double z)
{
// Take the hashed value and take the first 4 bits of it (15 == 0b1111)
int h = hash & 15;
// If the most significant bit (MSB) of the hash is 0 then set u = x. Otherwise y.
double u = h < 8 /* 0b1000 */ ? x : y;
double v;
// In Ken Perlin's original implementation this was another
// conditional operator (?:), then expanded for readability.
if (h < 4 /* 0b0100 */)
// If the first and second significant bits are 0 set v = y
v = y;
// If the first and second significant bits are 1 set v = x
else if (h == 12 /* 0b1100 */ || h == 14 /* 0b1110 */)
v = x;
else
// If the first and second significant bits are not equal (0/1, 1/0) set v = z
v = z;
// Use the last 2 bits to decide if u and v are positive or negative. Then return their addition.
return ((h&1) == 0 ? u : -u)+((h&2) == 0 ? v : -v);
}
static inline double fade(double t)
{
// Fade function as defined by Ken Perlin. This eases coordinate values
// so that they will "ease" towards integral values. This ends up smoothing
// the final output.
// use Horner method to compute: 6t^5 - 15t^4 + 10t^3
return t * t * t * (t * (t * 6 - 15) + 10);
}
static double lerp(double a, double b, double x)
{
return a + x * (b - a);
}
// Hash lookup table as defined by Ken Perlin. This is a randomly
// arranged array of all numbers from 0-255 inclusive.
static uint8_t ken_permutations[] = {
151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225,
140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148,
247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32,
57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175,
74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54,
65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169,
200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64,
52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212,
207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213,
119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104,
218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241,
81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93,
222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180
};
int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persistence,
enum FFPerlinRandomMode random_mode, unsigned int random_seed)
{
int i;
perlin->period = period;
perlin->octaves = octaves;
perlin->persistence = persistence;
perlin->random_mode = random_mode;
perlin->random_seed = random_seed;
if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_KEN) {
for (i = 0; i < 512; i++) {
perlin->permutations[i] = ken_permutations[i % 256];
}
} else {
AVLFG lfg;
uint8_t random_permutations[256];
if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_RANDOM)
perlin->random_seed = av_get_random_seed();
av_lfg_init(&lfg, perlin->random_seed);
for (i = 0; i < 256; i++) {
random_permutations[i] = i;
}
for (i = 0; i < 256; i++) {
unsigned int random_idx = av_lfg_get(&lfg) % (256-i);
uint8_t random_val = random_permutations[random_idx];
random_permutations[random_idx] = random_permutations[256-i];
perlin->permutations[i] = perlin->permutations[i+256] = random_val;
}
}
return 0;
}
static double perlin_get(FFPerlin *perlin, double x, double y, double z)
{
int xi, yi, zi;
double xf, yf, zf;
double u, v, w;
const uint8_t *p = perlin->permutations;
double period = perlin->period;
int aaa, aba, aab, abb, baa, bba, bab, bbb;
double x1, x2, y1, y2;
if (perlin->period > 0) {
// If we have any period on, change the coordinates to their "local" repetitions
x = fmod(x, perlin->period);
y = fmod(y, perlin->period);
z = fmod(z, perlin->period);
}
// Calculate the "unit cube" that the point asked will be located in
// The left bound is ( |_x_|,|_y_|,|_z_| ) and the right bound is that
// plus 1. Next we calculate the location (from 0.0 to 1.0) in that cube.
xi = (int)x & 255;
yi = (int)y & 255;
zi = (int)z & 255;
xf = x - (int)x;
yf = y - (int)y;
zf = z - (int)z;
// We also fade the location to smooth the result.
u = fade(xf);
v = fade(yf);
w = fade(zf);
aaa = p[p[p[ xi ] + yi ] + zi ];
aba = p[p[p[ xi ] + inc(yi, period)] + zi ];
aab = p[p[p[ xi ] + yi ] + inc(zi, period)];
abb = p[p[p[ xi ] + inc(yi, period)] + inc(zi, period)];
baa = p[p[p[inc(xi, period)] + yi ] + zi ];
bba = p[p[p[inc(xi, period)] + inc(yi, period)] + zi ];
bab = p[p[p[inc(xi, period)] + yi ] + inc(zi, period)];
bbb = p[p[p[inc(xi, period)] + inc(yi, period)] + inc(zi, period)];
// The gradient function calculates the dot product between a pseudorandom
// gradient vector and the vector from the input coordinate to the 8
// surrounding points in its unit cube.
// This is all then lerped together as a sort of weighted average based on the faded (u,v,w)
// values we made earlier.
x1 = lerp(grad(aaa, xf , yf , zf),
grad(baa, xf-1, yf , zf),
u);
x2 = lerp(grad(aba, xf , yf-1, zf),
grad(bba, xf-1, yf-1, zf),
u);
y1 = lerp(x1, x2, v);
x1 = lerp(grad(aab, xf , yf , zf-1),
grad(bab, xf-1, yf , zf-1),
u);
x2 = lerp(grad(abb, xf , yf-1, zf-1),
grad(bbb, xf-1, yf-1, zf-1),
u);
y2 = lerp(x1, x2, v);
// For convenience we bound it to 0 - 1 (theoretical min/max before is -1 - 1)
return (lerp(y1, y2, w) + 1) / 2;
}
double ff_perlin_get(FFPerlin *perlin, double x, double y, double z)
{
double total = 0;
double frequency = 1;
double amplitude = 1;
double max_value = 0; // Used for normalizing result to 0.0 - 1.0
for (int i = 0; i < perlin->octaves; i++) {
total += perlin_get(perlin, x * frequency, y * frequency, z * frequency) * amplitude;
max_value += amplitude;
amplitude *= perlin->persistence;
frequency *= 2;
}
return total / max_value;
}
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