modernc.org/ccgo/v3@v3.16.14/lib/testdata/CompCert-3.6/test/c/perlin.c (about)

     1  // perlin noise, derived from the Java reference implementation at 
     2  // http://mrl.nyu.edu/~perlin/noise/
     3  
     4  #include <math.h>
     5  #include <stdio.h>
     6  
     7  static int p[512];
     8  
     9  static int permutation[256] = { 151,160,137,91,90,15,
    10     131,13,201,95,96,53,194,233,7,225,140,36,103,30,69,142,8,99,37,240,21,10,23,
    11     190, 6,148,247,120,234,75,0,26,197,62,94,252,219,203,117,35,11,32,57,177,33,
    12     88,237,149,56,87,174,20,125,136,171,168, 68,175,74,165,71,134,139,48,27,166,
    13     77,146,158,231,83,111,229,122,60,211,133,230,220,105,92,41,55,46,245,40,244,
    14     102,143,54, 65,25,63,161, 1,216,80,73,209,76,132,187,208, 89,18,169,200,196,
    15     135,130,116,188,159,86,164,100,109,198,173,186, 3,64,52,217,226,250,124,123,
    16     5,202,38,147,118,126,255,82,85,212,207,206,59,227,47,16,58,17,182,189,28,42,
    17     223,183,170,213,119,248,152, 2,44,154,163, 70,221,153,101,155,167, 43,172,9,
    18     129,22,39,253, 19,98,108,110,79,113,224,232,178,185, 112,104,218,246,97,228,
    19     251,34,242,193,238,210,144,12,191,179,162,241, 81,51,145,235,249,14,239,107,
    20     49,192,214, 31,181,199,106,157,184, 84,204,176,115,121,50,45,127, 4,150,254,
    21     138,236,205,93,222,114,67,29,24,72,243,141,128,195,78,66,215,61,156,180
    22     };
    23  
    24  static inline double fade(double t)
    25  { return t * t * t * (t * (t * 6 - 15) + 10); }
    26  
    27  static inline double lerp(double t, double a, double b)
    28  { return a + t * (b - a); }
    29  
    30  static double grad(int hash, double x, double y, double z) {
    31    int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
    32    double u = h<8 ? x : y,                 // INTO 12 GRADIENT DIRECTIONS.
    33           v = h<4 ? y : h==12||h==14 ? x : z;
    34    return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
    35  }
    36  
    37  static double noise(double x, double y, double z) {
    38    int X = (int)floor(x) & 255,                  // FIND UNIT CUBE THAT
    39        Y = (int)floor(y) & 255,                  // CONTAINS POINT.
    40        Z = (int)floor(z) & 255;
    41    x -= floor(x);                                // FIND RELATIVE X,Y,Z
    42    y -= floor(y);                                // OF POINT IN CUBE.
    43    z -= floor(z);
    44    double u = fade(x),                                // COMPUTE FADE CURVES
    45           v = fade(y),                                // FOR EACH OF X,Y,Z.
    46           w = fade(z);
    47    int A = p[X  ]+Y, AA = p[A]+Z, AB = p[A+1]+Z,      // HASH COORDINATES OF
    48        B = p[X+1]+Y, BA = p[B]+Z, BB = p[B+1]+Z;      // THE 8 CUBE CORNERS,
    49  
    50    return lerp(w, lerp(v, lerp(u, grad(p[AA  ], x  , y  , z   ),  // AND ADD
    51                                   grad(p[BA  ], x-1, y  , z   )), // BLENDED
    52                           lerp(u, grad(p[AB  ], x  , y-1, z   ),  // RESULTS
    53                                   grad(p[BB  ], x-1, y-1, z   ))),// FROM  8
    54                   lerp(v, lerp(u, grad(p[AA+1], x  , y  , z-1 ),  // CORNERS
    55                                   grad(p[BA+1], x-1, y  , z-1 )), // OF CUBE
    56                           lerp(u, grad(p[AB+1], x  , y-1, z-1 ),
    57                                   grad(p[BB+1], x-1, y-1, z-1 ))));
    58  }
    59  
    60  static void init(void) { 
    61    int i = 0;
    62    for (i=0; i < 256 ; i++)
    63      p[256+i] = p[i] = permutation[i];
    64  }
    65  
    66  int main(int argc, char ** argv) {
    67    init();
    68    
    69    double x, y, z, sum = 0.0;
    70    for (x = -5.0; x < 5.0; x += 0.1)
    71      for (y = -5.0; y < 5.0; y += 0.1)
    72        for (z = -5.0; z < 5.0; z += 0.1)
    73          sum += noise(x, y, z);
    74    
    75    printf("%.4e\n", sum);
    76    return 0;
    77  }