// JAVA REFERENCE IMPLEMENTATION OF IMPROVED NOISE IN 4D - COPYRIGHT 2002 KEN PERLIN.

public final class ImprovedNoise4D {
   static public double noise(double x, double y, double z, double w) {
      int X = (int)Math.floor(x) & 255,                  // FIND UNIT HYPERCUBE
          Y = (int)Math.floor(y) & 255,                  // THAT CONTAINS POINT.
          Z = (int)Math.floor(z) & 255,
          W = (int)Math.floor(w) & 255;
      x -= Math.floor(x);                                // FIND RELATIVE X,Y,Z,W
      y -= Math.floor(y);                                // OF POINT IN CUBE.
      z -= Math.floor(z);
      w -= Math.floor(w);
      double a = fade(x),                                // COMPUTE FADE CURVES
             b = fade(y),                                // FOR EACH OF X,Y,Z,W.
             c = fade(z),
             d = fade(w);
      int A = p[X  ]+Y, AA = p[A]+Z, AB = p[A+1]+Z,      // HASH COORDINATES OF
          B = p[X+1]+Y, BA = p[B]+Z, BB = p[B+1]+Z,      // THE 16 CORNERS OF
          AAA = p[AA]+W, AAB = p[AA+1]+W,                // THE HYPERCUBE.
          ABA = p[AB]+W, ABB = p[AB+1]+W,
          BAA = p[BA]+W, BAB = p[BA+1]+W,
          BBA = p[BB]+W, BBB = p[BB+1]+W;

      return lerp(d,                                     // INTERPOLATE DOWN.
          lerp(c,lerp(b,lerp(a,grad(p[AAA  ], x  , y  , z  , w), 
                               grad(p[BAA  ], x-1, y  , z  , w)),
                        lerp(a,grad(p[ABA  ], x  , y-1, z  , w), 
                               grad(p[BBA  ], x-1, y-1, z  , w))),

                 lerp(b,lerp(a,grad(p[AAB  ], x  , y  , z-1, w), 
                               grad(p[BAB  ], x-1, y  , z-1, w)),
                        lerp(a,grad(p[ABB  ], x  , y-1, z-1, w),
                               grad(p[BBB  ], x-1, y-1, z-1, w)))),

          lerp(c,lerp(b,lerp(a,grad(p[AAA+1], x  , y  , z  , w-1), 
                               grad(p[BAA+1], x-1, y  , z  , w-1)),
                        lerp(a,grad(p[ABA+1], x  , y-1, z  , w-1), 
                               grad(p[BBA+1], x-1, y-1, z  , w-1))),

                 lerp(b,lerp(a,grad(p[AAB+1], x  , y  , z-1, w-1), 
                               grad(p[BAB+1], x-1, y  , z-1, w-1)),
                        lerp(a,grad(p[ABB+1], x  , y-1, z-1, w-1),
                               grad(p[BBB+1], x-1, y-1, z-1, w-1)))));
   }
   static double fade(double t) { return t * t * t * (t * (t * 6 - 15) + 10); }
   static double lerp(double t, double a, double b) { return a + t * (b - a); }
   static double grad(int hash, double x, double y, double z, double w) {
      int h = hash & 31; // CONVERT LO 5 BITS OF HASH TO 32 GRAD DIRECTIONS.
      double a=y,b=z,c=w;            // X,Y,Z
      switch (h >> 3) {          // OR, DEPENDING ON HIGH ORDER 2 BITS:
      case 1: a=w;b=x;c=y;break;     // W,X,Y
      case 2: a=z;b=w;c=x;break;     // Z,W,X
      case 3: a=y;b=z;c=w;break;     // Y,Z,W
      }
      return ((h&4)==0 ? -a:a) + ((h&2)==0 ? -b:b) + ((h&1)==0 ? -c:c);
   }
   static final int p[] = new int[512], permutation[] = { 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
   };
   static { for (int i=0; i < 256 ; i++) p[256+i] = p[i] = permutation[i]; }
}