content: /*****************************************************************************
   *                        Shapeways, Inc Copyright (c) 2011
   *                               Java Source
   *
   * This source is licensed under the GNU LGPL v2.1
   * Please read http://www.gnu.org/copyleft/lgpl.html for more information
   *
   * This software comes with the standard NO WARRANTY disclaimer for any
   * purpose. Use it at your own risk. If there's a problem you get to fix it.
   *
   ****************************************************************************/
  
  
  package abfab3d.util;
  
  import java.util.Random;
  
  import static abfab3d.core.Output.printf;
  
  
  // JAVA REFERENCE IMPLEMENTATION OF IMPROVED NOISE - COPYRIGHT 2002 KEN PERLIN.
  
  public final class SimplexNoisePerlin {
  
      int p[] = new int[512];
      
      public SimplexNoisePerlin(int seed){
          
          init(seed);
          
      }
      
      void init(int seed){
          
          int perm[]=null;
          switch(seed){
          case 0: 
              perm = permutation_orig; 
              break;
          case 1: 
              perm = makeIdentity();
              break;
          default:
              perm = makePerm(seed);
          }
          
          copyPerm(perm, p);
          
      }
      
      /**
         return array of 256 different numbers with given seed
      */
      static int[] makePerm(int seed){
          
          int perm[] = new int[256];
          int key[] = new int[256];
          Random r = new Random(seed);
          r.nextInt(256); // skip first number. It is changes little with small changes in seed 
          int k = 0, m=0;
          while(k < 256){
              int n = r.nextInt(256);
              m++;
              if(key[n] == 0){
                  // new number it is accepted 
                  perm[k++] = n;
                  key[n] = 1;        
              }
          }
          printf("m: %d\n\n",m);
          return perm;
      }
      
      int [] makeIdentity(){
          int perm[] = new int[256];
          for(int i = 0; i < 256; i++){
              perm[i] = i;
          }
          return perm;
      }
      
      static void copyPerm(int src[], int dest[]){
          
          for (int i=0; i < 256 ; i++) 
              dest[256+i] = dest[i] = src[i];
          
      }
      
      static final int ifloor(double x){
          if(x >= 0.0) return (int)x;
          else return (int)x -1;
      }
      
      public double noise(double x, double y, double z) {
          
          int 
              X = ifloor(x),                  // FIND UNIT CUBE THAT
              Y = ifloor(y),                  // CONTAINS POINT.
              Z = ifloor(z);
          
          x -= X;    // FIND RELATIVE X,Y,Z
          y -= Y;                                // OF POINT IN CUBE.
          z -= Z;
          X &= 0xFF;
          Y &= 0xFF;
          Z &= 0xFF;
          
          double 
              u = fade(x),                                // COMPUTE FADE CURVES
              v = fade(y),                                // FOR EACH OF X,Y,Z.
              w = fade(z);
          
          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 8 CUBE CORNERS,
          
          // add blended results from 8 corners of cube 
          return lerp(w, lerp(v, 
                              lerp(u, 
                                   grad(p[AA], x, y, z), 
                                   grad(p[BA], x-1, y  , z)),
                              lerp(u, 
                                   grad(p[AB], x, y-1, z),  
                                   grad(p[BB], x-1, y-1, z))),
                      lerp(v, lerp(u, 
                                   grad(p[AA+1], x  , y  , z-1 ),
                                   grad(p[BA+1], x-1, y  , z-1 )),
                           lerp(u, 
                                grad(p[AB+1], x  , y-1, z-1 ),
                                grad(p[BB+1], x-1, y-1, z-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); 
      }
      
      public double turbulence(double x, double y, double z, int octaves, double persistence) {
          
          double total = 0;
          double freq = 1;
          double amp = 1;
          
          for(int i  = 0; i < octaves; i++){
              
              total += noise(x * freq, y * freq, z * freq) * amp;
              freq = freq*2;
              amp *= persistence;
          }
          
          return total;
          
      }
      
      /**
         gradient is not random.
         it is one of 12 directions from center to the edges of the cube
         (1,1,0),(-1,1,0),(1,-1,0),(-1,-1,0),  
         (1,0,1),(-1,0,1),(1,0,-1),(-1,0,-1),  
         (0,1,1),(0,-1,1),(0,1,-1),(0,-1,-1) 
      */
      static double grad(int hash, double x, double y, double z) {
          int h = hash & 15;                      // CONVERT LO 4 BITS OF HASH CODE
          double u = h<8 ? x : y;                 // INTO 12 GRADIENT DIRECTIONS.
          double v = h<4 ? y : h==12||h==14 ? x : z;
          
          return ((h&1) == 0 ? u : -u) + ((h&2) == 0 ? v : -v);
      }
      
      static final int  permutation_orig[] = { 
          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
      };        
  }
  