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6d9c4bd69e
An incorrect calculation in ff_perlin_init causes a write to the stack array at index 256, which is out of bounds. Fixes: CID1608711 Reviewed-by: Stefano Sabatini <stefasab@gmail.com> Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
225 lines
8.1 KiB
C
225 lines
8.1 KiB
C
/*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with FFmpeg; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*/
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/**
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* @file
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* Perlin Noise generator, based on code from:
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* https://adrianb.io/2014/08/09/perlinnoise.html
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*
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* Original article from Ken Perlin:
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* http://mrl.nyu.edu/~perlin/paper445.pdf
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*/
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#include <math.h>
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#include "libavutil/lfg.h"
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#include "libavutil/random_seed.h"
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#include "perlin.h"
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static inline int inc(int num, int period)
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{
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num++;
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if (period > 0)
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num %= period;
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return num;
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}
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static inline double grad(int hash, double x, double y, double z)
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{
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// Take the hashed value and take the first 4 bits of it (15 == 0b1111)
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int h = hash & 15;
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// If the most significant bit (MSB) of the hash is 0 then set u = x. Otherwise y.
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double u = h < 8 /* 0b1000 */ ? x : y;
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double v;
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// In Ken Perlin's original implementation this was another
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// conditional operator (?:), then expanded for readability.
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if (h < 4 /* 0b0100 */)
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// If the first and second significant bits are 0 set v = y
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v = y;
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// If the first and second significant bits are 1 set v = x
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else if (h == 12 /* 0b1100 */ || h == 14 /* 0b1110 */)
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v = x;
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else
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// If the first and second significant bits are not equal (0/1, 1/0) set v = z
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v = z;
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// Use the last 2 bits to decide if u and v are positive or negative. Then return their addition.
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return ((h&1) == 0 ? u : -u)+((h&2) == 0 ? v : -v);
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}
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static inline double fade(double t)
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{
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// Fade function as defined by Ken Perlin. This eases coordinate values
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// so that they will "ease" towards integral values. This ends up smoothing
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// the final output.
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// use Horner method to compute: 6t^5 - 15t^4 + 10t^3
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return t * t * t * (t * (t * 6 - 15) + 10);
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}
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static double lerp(double a, double b, double x)
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{
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return a + x * (b - a);
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}
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// Hash lookup table as defined by Ken Perlin. This is a randomly
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// arranged array of all numbers from 0-255 inclusive.
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static uint8_t ken_permutations[] = {
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151, 160, 137, 91, 90, 15, 131, 13, 201, 95, 96, 53, 194, 233, 7, 225,
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140, 36, 103, 30, 69, 142, 8, 99, 37, 240, 21, 10, 23, 190, 6, 148,
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247, 120, 234, 75, 0, 26, 197, 62, 94, 252, 219, 203, 117, 35, 11, 32,
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57, 177, 33, 88, 237, 149, 56, 87, 174, 20, 125, 136, 171, 168, 68, 175,
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74, 165, 71, 134, 139, 48, 27, 166, 77, 146, 158, 231, 83, 111, 229, 122,
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60, 211, 133, 230, 220, 105, 92, 41, 55, 46, 245, 40, 244, 102, 143, 54,
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65, 25, 63, 161, 1, 216, 80, 73, 209, 76, 132, 187, 208, 89, 18, 169,
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200, 196, 135, 130, 116, 188, 159, 86, 164, 100, 109, 198, 173, 186, 3, 64,
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52, 217, 226, 250, 124, 123, 5, 202, 38, 147, 118, 126, 255, 82, 85, 212,
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207, 206, 59, 227, 47, 16, 58, 17, 182, 189, 28, 42, 223, 183, 170, 213,
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119, 248, 152, 2, 44, 154, 163, 70, 221, 153, 101, 155, 167, 43, 172, 9,
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129, 22, 39, 253, 19, 98, 108, 110, 79, 113, 224, 232, 178, 185, 112, 104,
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218, 246, 97, 228, 251, 34, 242, 193, 238, 210, 144, 12, 191, 179, 162, 241,
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81, 51, 145, 235, 249, 14, 239, 107, 49, 192, 214, 31, 181, 199, 106, 157,
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184, 84, 204, 176, 115, 121, 50, 45, 127, 4, 150, 254, 138, 236, 205, 93,
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222, 114, 67, 29, 24, 72, 243, 141, 128, 195, 78, 66, 215, 61, 156, 180
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};
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int ff_perlin_init(FFPerlin *perlin, double period, int octaves, double persistence,
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enum FFPerlinRandomMode random_mode, unsigned int random_seed)
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{
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int i;
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perlin->period = period;
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perlin->octaves = octaves;
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perlin->persistence = persistence;
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perlin->random_mode = random_mode;
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perlin->random_seed = random_seed;
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if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_KEN) {
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for (i = 0; i < 512; i++) {
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perlin->permutations[i] = ken_permutations[i % 256];
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}
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} else {
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AVLFG lfg;
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uint8_t random_permutations[256];
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if (perlin->random_mode == FF_PERLIN_RANDOM_MODE_RANDOM)
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perlin->random_seed = av_get_random_seed();
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av_lfg_init(&lfg, perlin->random_seed);
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for (i = 0; i < 256; i++) {
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random_permutations[i] = i;
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}
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for (i = 0; i < 256; i++) {
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unsigned int random_idx = av_lfg_get(&lfg) % (256-i);
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uint8_t random_val = random_permutations[random_idx];
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random_permutations[random_idx] = random_permutations[255-i];
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perlin->permutations[i] = perlin->permutations[i+256] = random_val;
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}
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}
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return 0;
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}
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static double perlin_get(FFPerlin *perlin, double x, double y, double z)
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{
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int xi, yi, zi;
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double xf, yf, zf;
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double u, v, w;
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const uint8_t *p = perlin->permutations;
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double period = perlin->period;
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int aaa, aba, aab, abb, baa, bba, bab, bbb;
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double x1, x2, y1, y2;
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if (perlin->period > 0) {
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// If we have any period on, change the coordinates to their "local" repetitions
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x = fmod(x, perlin->period);
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y = fmod(y, perlin->period);
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z = fmod(z, perlin->period);
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}
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// Calculate the "unit cube" that the point asked will be located in
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// The left bound is ( |_x_|,|_y_|,|_z_| ) and the right bound is that
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// plus 1. Next we calculate the location (from 0.0 to 1.0) in that cube.
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xi = (int)x & 255;
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yi = (int)y & 255;
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zi = (int)z & 255;
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xf = x - (int)x;
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yf = y - (int)y;
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zf = z - (int)z;
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// We also fade the location to smooth the result.
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u = fade(xf);
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v = fade(yf);
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w = fade(zf);
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aaa = p[p[p[ xi ] + yi ] + zi ];
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aba = p[p[p[ xi ] + inc(yi, period)] + zi ];
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aab = p[p[p[ xi ] + yi ] + inc(zi, period)];
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abb = p[p[p[ xi ] + inc(yi, period)] + inc(zi, period)];
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baa = p[p[p[inc(xi, period)] + yi ] + zi ];
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bba = p[p[p[inc(xi, period)] + inc(yi, period)] + zi ];
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bab = p[p[p[inc(xi, period)] + yi ] + inc(zi, period)];
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bbb = p[p[p[inc(xi, period)] + inc(yi, period)] + inc(zi, period)];
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// The gradient function calculates the dot product between a pseudorandom
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// gradient vector and the vector from the input coordinate to the 8
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// surrounding points in its unit cube.
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// This is all then lerped together as a sort of weighted average based on the faded (u,v,w)
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// values we made earlier.
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x1 = lerp(grad(aaa, xf , yf , zf),
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grad(baa, xf-1, yf , zf),
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u);
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x2 = lerp(grad(aba, xf , yf-1, zf),
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grad(bba, xf-1, yf-1, zf),
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u);
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y1 = lerp(x1, x2, v);
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x1 = lerp(grad(aab, xf , yf , zf-1),
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grad(bab, xf-1, yf , zf-1),
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u);
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x2 = lerp(grad(abb, xf , yf-1, zf-1),
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grad(bbb, xf-1, yf-1, zf-1),
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u);
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y2 = lerp(x1, x2, v);
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// For convenience we bound it to 0 - 1 (theoretical min/max before is -1 - 1)
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return (lerp(y1, y2, w) + 1) / 2;
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}
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double ff_perlin_get(FFPerlin *perlin, double x, double y, double z)
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{
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double total = 0;
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double frequency = 1;
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double amplitude = 1;
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double max_value = 0; // Used for normalizing result to 0.0 - 1.0
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for (int i = 0; i < perlin->octaves; i++) {
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total += perlin_get(perlin, x * frequency, y * frequency, z * frequency) * amplitude;
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max_value += amplitude;
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amplitude *= perlin->persistence;
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frequency *= 2;
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}
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return total / max_value;
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}
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