content: package thebetweenlands.util;
  
  /*
   * OpenSimplex (Simplectic) Noise in Java.
   * by Kurt Spencer
   * 
   * v1.1 (October 5, 2014)
   * - Added 2D and 4D implementations.
   * - Proper gradient sets for all dimensions, from a
   *   dimensionally-generalizable scheme with an actual
   *   rhyme and reason behind it.
   * - Removed default permutation array in favor of
   *   default seed.
   * - Changed seed-based constructor to be independent
   *   of any particular randomization library, so results
   *   will be the same when ported to other languages.
   */
  
  public class OpenSimplexNoise {
  
      private static final double STRETCH_CONSTANT_2D = -0.211324865405187; // (1/Math.sqrt(2+1)-1)/2;
      private static final double SQUISH_CONSTANT_2D = 0.366025403784439; // (Math.sqrt(2+1)-1)/2;
      private static final double STRETCH_CONSTANT_3D = -1.0 / 6; // (1/Math.sqrt(3+1)-1)/3;
      private static final double SQUISH_CONSTANT_3D = 1.0 / 3; // (Math.sqrt(3+1)-1)/3;
      private static final double STRETCH_CONSTANT_4D = -0.138196601125011; // (1/Math.sqrt(4+1)-1)/4;
      private static final double SQUISH_CONSTANT_4D = 0.309016994374947; // (Math.sqrt(4+1)-1)/4;
  
      private static final double NORM_CONSTANT_2D = 47;
      private static final double NORM_CONSTANT_3D = 103;
      private static final double NORM_CONSTANT_4D = 30;
  
      private static final long DEFAULT_SEED = 0;
  
      private short[] perm;
      private short[] permGradIndex3D;
  
      public OpenSimplexNoise() {
          this(DEFAULT_SEED);
      }
  
      public OpenSimplexNoise(short[] perm) {
          this.perm = perm;
          permGradIndex3D = new short[256];
  
          for (int i = 0; i < 256; i++) {
              // Since 3D has 24 gradients, simple bitmask won't work, so precompute modulo array.
              permGradIndex3D[i] = (short) ((perm[i] % (gradients3D.length / 3)) * 3);
          }
      }
  
      // Initializes the class using a permutation array generated from a 64-bit seed.
      // Generates a proper permutation (i.e. doesn't merely perform N successive pair swaps on a base array)
      // Uses a simple 64-bit LCG.
      public OpenSimplexNoise(long seed) {
          perm = new short[256];
          permGradIndex3D = new short[256];
          short[] source = new short[256];
          for (short i = 0; i < 256; i++)
              source[i] = i;
          seed = seed * 6364136223846793005l + 1442695040888963407l;
          seed = seed * 6364136223846793005l + 1442695040888963407l;
          seed = seed * 6364136223846793005l + 1442695040888963407l;
          for (int i = 255; i >= 0; i--) {
              seed = seed * 6364136223846793005l + 1442695040888963407l;
              int r = (int) ((seed + 31) % (i + 1));
              if (r < 0)
                  r += (i + 1);
              perm[i] = source[r];
              permGradIndex3D[i] = (short) ((perm[i] % (gradients3D.length / 3)) * 3);
              source[r] = source[i];
          }
      }
  
      // 2D OpenSimplex (Simplectic) Noise.
      public double eval(double x, double y) {
  
          // Place input coordinates onto grid.
          double stretchOffset = (x + y) * STRETCH_CONSTANT_2D;
          double xs = x + stretchOffset;
          double ys = y + stretchOffset;
  
          // Floor to get grid coordinates of rhombus (stretched square) super-cell origin.
          int xsb = fastFloor(xs);
          int ysb = fastFloor(ys);
  
          // Skew out to get actual coordinates of rhombus origin. We'll need these later.
          double squishOffset = (xsb + ysb) * SQUISH_CONSTANT_2D;
          double xb = xsb + squishOffset;
          double yb = ysb + squishOffset;
  
          // Compute grid coordinates relative to rhombus origin.
          double xins = xs - xsb;
          double yins = ys - ysb;
  
          // Sum those together to get a value that determines which region we're in.
          double inSum = xins + yins;
  
          // Positions relative to origin point.
          double dx0 = x - xb;
          double dy0 = y - yb;
  
          // We'll be defining these inside the next block and using them afterwards.
          double dx_ext, dy_ext;
          int xsv_ext, ysv_ext;
  
          double value = 0;
  
          // Contribution (1,0)
          double dx1 = dx0 - 1 - SQUISH_CONSTANT_2D;
          double dy1 = dy0 - 0 - SQUISH_CONSTANT_2D;
          double attn1 = 2 - dx1 * dx1 - dy1 * dy1;
          if (attn1 > 0) {
              attn1 *= attn1;
              value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, dx1, dy1);
          }
  
          // Contribution (0,1)
          double dx2 = dx0 - 0 - SQUISH_CONSTANT_2D;
          double dy2 = dy0 - 1 - SQUISH_CONSTANT_2D;
          double attn2 = 2 - dx2 * dx2 - dy2 * dy2;
          if (attn2 > 0) {
              attn2 *= attn2;
              value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, dx2, dy2);
          }
  
          if (inSum <= 1) { // We're inside the triangle (2-Simplex) at (0,0)
              double zins = 1 - inSum;
              if (zins > xins || zins > yins) { // (0,0) is one of the closest two triangular vertices
                  if (xins > yins) {
                      xsv_ext = xsb + 1;
                      ysv_ext = ysb - 1;
                      dx_ext = dx0 - 1;
                      dy_ext = dy0 + 1;
                  } else {
                      xsv_ext = xsb - 1;
                      ysv_ext = ysb + 1;
                      dx_ext = dx0 + 1;
                      dy_ext = dy0 - 1;
                  }
              } else { // (1,0) and (0,1) are the closest two vertices.
                  xsv_ext = xsb + 1;
                  ysv_ext = ysb + 1;
                  dx_ext = dx0 - 1 - 2 * SQUISH_CONSTANT_2D;
                  dy_ext = dy0 - 1 - 2 * SQUISH_CONSTANT_2D;
              }
          } else { // We're inside the triangle (2-Simplex) at (1,1)
              double zins = 2 - inSum;
              if (zins < xins || zins < yins) { // (0,0) is one of the closest two triangular vertices
                  if (xins > yins) {
                      xsv_ext = xsb + 2;
                      ysv_ext = ysb + 0;
                      dx_ext = dx0 - 2 - 2 * SQUISH_CONSTANT_2D;
                      dy_ext = dy0 + 0 - 2 * SQUISH_CONSTANT_2D;
                  } else {
                      xsv_ext = xsb + 0;
                      ysv_ext = ysb + 2;
                      dx_ext = dx0 + 0 - 2 * SQUISH_CONSTANT_2D;
                      dy_ext = dy0 - 2 - 2 * SQUISH_CONSTANT_2D;
                  }
              } else { // (1,0) and (0,1) are the closest two vertices.
                  dx_ext = dx0;
                  dy_ext = dy0;
                  xsv_ext = xsb;
                  ysv_ext = ysb;
              }
              xsb += 1;
              ysb += 1;
              dx0 = dx0 - 1 - 2 * SQUISH_CONSTANT_2D;
              dy0 = dy0 - 1 - 2 * SQUISH_CONSTANT_2D;
          }
  
          // Contribution (0,0) or (1,1)
          double attn0 = 2 - dx0 * dx0 - dy0 * dy0;
          if (attn0 > 0) {
              attn0 *= attn0;
              value += attn0 * attn0 * extrapolate(xsb, ysb, dx0, dy0);
          }
  
          // Extra Vertex
          double attn_ext = 2 - dx_ext * dx_ext - dy_ext * dy_ext;
          if (attn_ext > 0) {
              attn_ext *= attn_ext;
              value += attn_ext * attn_ext * extrapolate(xsv_ext, ysv_ext, dx_ext, dy_ext);
          }
  
          return value / NORM_CONSTANT_2D;
      }
  
      // 3D OpenSimplex (Simplectic) Noise.
      public double eval(double x, double y, double z) {
  
          // Place input coordinates on simplectic honeycomb.
          double stretchOffset = (x + y + z) * STRETCH_CONSTANT_3D;
          double xs = x + stretchOffset;
          double ys = y + stretchOffset;
          double zs = z + stretchOffset;
  
          // Floor to get simplectic honeycomb coordinates of rhombohedron (stretched cube) super-cell origin.
          int xsb = fastFloor(xs);
          int ysb = fastFloor(ys);
          int zsb = fastFloor(zs);
  
          // Skew out to get actual coordinates of rhombohedron origin. We'll need these later.
          double squishOffset = (xsb + ysb + zsb) * SQUISH_CONSTANT_3D;
          double xb = xsb + squishOffset;
          double yb = ysb + squishOffset;
          double zb = zsb + squishOffset;
  
          // Compute simplectic honeycomb coordinates relative to rhombohedral origin.
          double xins = xs - xsb;
          double yins = ys - ysb;
          double zins = zs - zsb;
  
          // Sum those together to get a value that determines which region we're in.
          double inSum = xins + yins + zins;
  
          // Positions relative to origin point.
          double dx0 = x - xb;
          double dy0 = y - yb;
          double dz0 = z - zb;
  
          // We'll be defining these inside the next block and using them afterwards.
          double dx_ext0, dy_ext0, dz_ext0;
          double dx_ext1, dy_ext1, dz_ext1;
          int xsv_ext0, ysv_ext0, zsv_ext0;
          int xsv_ext1, ysv_ext1, zsv_ext1;
  
          double value = 0;
          if (inSum <= 1) { // We're inside the tetrahedron (3-Simplex) at (0,0,0)
  
              // Determine which two of (0,0,1), (0,1,0), (1,0,0) are closest.
              byte aPoint = 0x01;
              double aScore = xins;
              byte bPoint = 0x02;
              double bScore = yins;
              if (aScore >= bScore && zins > bScore) {
                  bScore = zins;
                  bPoint = 0x04;
              } else if (aScore < bScore && zins > aScore) {
                  aScore = zins;
                  aPoint = 0x04;
              }
  
              // Now we determine the two lattice points not part of the tetrahedron that may contribute.
              // This depends on the closest two tetrahedral vertices, including (0,0,0)
              double wins = 1 - inSum;
              if (wins > aScore || wins > bScore) { // (0,0,0) is one of the closest two tetrahedral vertices.
                  byte c = (bScore > aScore ? bPoint : aPoint); // Our other closest vertex is the closest out of a and b.
  
                  if ((c & 0x01) == 0) {
                      xsv_ext0 = xsb - 1;
                      xsv_ext1 = xsb;
                      dx_ext0 = dx0 + 1;
                      dx_ext1 = dx0;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb + 1;
                      dx_ext0 = dx_ext1 = dx0 - 1;
                  }
  
                  if ((c & 0x02) == 0) {
                      ysv_ext0 = ysv_ext1 = ysb;
                      dy_ext0 = dy_ext1 = dy0;
                      if ((c & 0x01) == 0) {
                          ysv_ext1 -= 1;
                          dy_ext1 += 1;
                      } else {
                          ysv_ext0 -= 1;
                          dy_ext0 += 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy0 - 1;
                  }
  
                  if ((c & 0x04) == 0) {
                      zsv_ext0 = zsb;
                      zsv_ext1 = zsb - 1;
                      dz_ext0 = dz0;
                      dz_ext1 = dz0 + 1;
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb + 1;
                      dz_ext0 = dz_ext1 = dz0 - 1;
                  }
              } else { // (0,0,0) is not one of the closest two tetrahedral vertices.
                  byte c = (byte) (aPoint | bPoint); // Our two extra vertices are determined by the closest two.
  
                  if ((c & 0x01) == 0) {
                      xsv_ext0 = xsb;
                      xsv_ext1 = xsb - 1;
                      dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_3D;
                      dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_3D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb + 1;
                      dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D;
                      dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x02) == 0) {
                      ysv_ext0 = ysb;
                      ysv_ext1 = ysb - 1;
                      dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_3D;
                      dy_ext1 = dy0 + 1 - SQUISH_CONSTANT_3D;
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb + 1;
                      dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D;
                      dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x04) == 0) {
                      zsv_ext0 = zsb;
                      zsv_ext1 = zsb - 1;
                      dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_3D;
                      dz_ext1 = dz0 + 1 - SQUISH_CONSTANT_3D;
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb + 1;
                      dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D;
                      dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D;
                  }
              }
  
              // Contribution (0,0,0)
              double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0;
              if (attn0 > 0) {
                  attn0 *= attn0;
                  value += attn0 * attn0 * extrapolate(xsb + 0, ysb + 0, zsb + 0, dx0, dy0, dz0);
              }
  
              // Contribution (1,0,0)
              double dx1 = dx0 - 1 - SQUISH_CONSTANT_3D;
              double dy1 = dy0 - 0 - SQUISH_CONSTANT_3D;
              double dz1 = dz0 - 0 - SQUISH_CONSTANT_3D;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, zsb + 0, dx1, dy1, dz1);
              }
  
              // Contribution (0,1,0)
              double dx2 = dx0 - 0 - SQUISH_CONSTANT_3D;
              double dy2 = dy0 - 1 - SQUISH_CONSTANT_3D;
              double dz2 = dz1;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, zsb + 0, dx2, dy2, dz2);
              }
  
              // Contribution (0,0,1)
              double dx3 = dx2;
              double dy3 = dy1;
              double dz3 = dz0 - 1 - SQUISH_CONSTANT_3D;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 0, ysb + 0, zsb + 1, dx3, dy3, dz3);
              }
          } else if (inSum >= 2) { // We're inside the tetrahedron (3-Simplex) at (1,1,1)
  
              // Determine which two tetrahedral vertices are the closest, out of (1,1,0), (1,0,1), (0,1,1) but not (1,1,1).
              byte aPoint = 0x06;
              double aScore = xins;
              byte bPoint = 0x05;
              double bScore = yins;
              if (aScore <= bScore && zins < bScore) {
                  bScore = zins;
                  bPoint = 0x03;
              } else if (aScore > bScore && zins < aScore) {
                  aScore = zins;
                  aPoint = 0x03;
              }
  
              // Now we determine the two lattice points not part of the tetrahedron that may contribute.
              // This depends on the closest two tetrahedral vertices, including (1,1,1)
              double wins = 3 - inSum;
              if (wins < aScore || wins < bScore) { // (1,1,1) is one of the closest two tetrahedral vertices.
                  byte c = (bScore < aScore ? bPoint : aPoint); // Our other closest vertex is the closest out of a and b.
  
                  if ((c & 0x01) != 0) {
                      xsv_ext0 = xsb + 2;
                      xsv_ext1 = xsb + 1;
                      dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_3D;
                      dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb;
                      dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x02) != 0) {
                      ysv_ext0 = ysv_ext1 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D;
                      if ((c & 0x01) != 0) {
                          ysv_ext1 += 1;
                          dy_ext1 -= 1;
                      } else {
                          ysv_ext0 += 1;
                          dy_ext0 -= 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb;
                      dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x04) != 0) {
                      zsv_ext0 = zsb + 1;
                      zsv_ext1 = zsb + 2;
                      dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D;
                      dz_ext1 = dz0 - 2 - 3 * SQUISH_CONSTANT_3D;
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb;
                      dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_3D;
                  }
              } else { // (1,1,1) is not one of the closest two tetrahedral vertices.
                  byte c = (byte) (aPoint & bPoint); // Our two extra vertices are determined by the closest two.
  
                  if ((c & 0x01) != 0) {
                      xsv_ext0 = xsb + 1;
                      xsv_ext1 = xsb + 2;
                      dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D;
                      dx_ext1 = dx0 - 2 - 2 * SQUISH_CONSTANT_3D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb;
                      dx_ext0 = dx0 - SQUISH_CONSTANT_3D;
                      dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x02) != 0) {
                      ysv_ext0 = ysb + 1;
                      ysv_ext1 = ysb + 2;
                      dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D;
                      dy_ext1 = dy0 - 2 - 2 * SQUISH_CONSTANT_3D;
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb;
                      dy_ext0 = dy0 - SQUISH_CONSTANT_3D;
                      dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D;
                  }
  
                  if ((c & 0x04) != 0) {
                      zsv_ext0 = zsb + 1;
                      zsv_ext1 = zsb + 2;
                      dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D;
                      dz_ext1 = dz0 - 2 - 2 * SQUISH_CONSTANT_3D;
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb;
                      dz_ext0 = dz0 - SQUISH_CONSTANT_3D;
                      dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D;
                  }
              }
  
              // Contribution (1,1,0)
              double dx3 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double dy3 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double dz3 = dz0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 1, ysb + 1, zsb + 0, dx3, dy3, dz3);
              }
  
              // Contribution (1,0,1)
              double dx2 = dx3;
              double dy2 = dy0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double dz2 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 1, ysb + 0, zsb + 1, dx2, dy2, dz2);
              }
  
              // Contribution (0,1,1)
              double dx1 = dx0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double dy1 = dy3;
              double dz1 = dz2;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 0, ysb + 1, zsb + 1, dx1, dy1, dz1);
              }
  
              // Contribution (1,1,1)
              dx0 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D;
              dy0 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D;
              dz0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D;
              double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0;
              if (attn0 > 0) {
                  attn0 *= attn0;
                  value += attn0 * attn0 * extrapolate(xsb + 1, ysb + 1, zsb + 1, dx0, dy0, dz0);
              }
          } else { // We're inside the octahedron (Rectified 3-Simplex) in between.
              double aScore;
              byte aPoint;
              boolean aIsFurtherSide;
              double bScore;
              byte bPoint;
              boolean bIsFurtherSide;
  
              // Decide between point (0,0,1) and (1,1,0) as closest
              double p1 = xins + yins;
              if (p1 > 1) {
                  aScore = p1 - 1;
                  aPoint = 0x03;
                  aIsFurtherSide = true;
              } else {
                  aScore = 1 - p1;
                  aPoint = 0x04;
                  aIsFurtherSide = false;
              }
  
              // Decide between point (0,1,0) and (1,0,1) as closest
              double p2 = xins + zins;
              if (p2 > 1) {
                  bScore = p2 - 1;
                  bPoint = 0x05;
                  bIsFurtherSide = true;
              } else {
                  bScore = 1 - p2;
                  bPoint = 0x02;
                  bIsFurtherSide = false;
              }
  
              // The closest out of the two (1,0,0) and (0,1,1) will replace the furthest out of the two decided above, if closer.
              double p3 = yins + zins;
              if (p3 > 1) {
                  double score = p3 - 1;
                  if (aScore <= bScore && aScore < score) {
                      aScore = score;
                      aPoint = 0x06;
                      aIsFurtherSide = true;
                  } else if (aScore > bScore && bScore < score) {
                      bScore = score;
                      bPoint = 0x06;
                      bIsFurtherSide = true;
                  }
              } else {
                  double score = 1 - p3;
                  if (aScore <= bScore && aScore < score) {
                      aScore = score;
                      aPoint = 0x01;
                      aIsFurtherSide = false;
                  } else if (aScore > bScore && bScore < score) {
                      bScore = score;
                      bPoint = 0x01;
                      bIsFurtherSide = false;
                  }
              }
  
              // Where each of the two closest points are determines how the extra two vertices are calculated.
              if (aIsFurtherSide == bIsFurtherSide) {
                  if (aIsFurtherSide) { // Both closest points on (1,1,1) side
  
                      // One of the two extra points is (1,1,1)
                      dx_ext0 = dx0 - 1 - 3 * SQUISH_CONSTANT_3D;
                      dy_ext0 = dy0 - 1 - 3 * SQUISH_CONSTANT_3D;
                      dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_3D;
                      xsv_ext0 = xsb + 1;
                      ysv_ext0 = ysb + 1;
                      zsv_ext0 = zsb + 1;
  
                      // Other extra point is based on the shared axis.
                      byte c = (byte) (aPoint & bPoint);
                      if ((c & 0x01) != 0) {
                          dx_ext1 = dx0 - 2 - 2 * SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb + 2;
                          ysv_ext1 = ysb;
                          zsv_ext1 = zsb;
                      } else if ((c & 0x02) != 0) {
                          dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 - 2 - 2 * SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb;
                          ysv_ext1 = ysb + 2;
                          zsv_ext1 = zsb;
                      } else {
                          dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 - 2 - 2 * SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb;
                          ysv_ext1 = ysb;
                          zsv_ext1 = zsb + 2;
                      }
                  } else {// Both closest points on (0,0,0) side
  
                      // One of the two extra points is (0,0,0)
                      dx_ext0 = dx0;
                      dy_ext0 = dy0;
                      dz_ext0 = dz0;
                      xsv_ext0 = xsb;
                      ysv_ext0 = ysb;
                      zsv_ext0 = zsb;
  
                      // Other extra point is based on the omitted axis.
                      byte c = (byte) (aPoint | bPoint);
                      if ((c & 0x01) == 0) {
                          dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb - 1;
                          ysv_ext1 = ysb + 1;
                          zsv_ext1 = zsb + 1;
                      } else if ((c & 0x02) == 0) {
                          dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 + 1 - SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb + 1;
                          ysv_ext1 = ysb - 1;
                          zsv_ext1 = zsb + 1;
                      } else {
                          dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_3D;
                          dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_3D;
                          dz_ext1 = dz0 + 1 - SQUISH_CONSTANT_3D;
                          xsv_ext1 = xsb + 1;
                          ysv_ext1 = ysb + 1;
                          zsv_ext1 = zsb - 1;
                      }
                  }
              } else { // One point on (0,0,0) side, one point on (1,1,1) side
                  byte c1, c2;
                  if (aIsFurtherSide) {
                      c1 = aPoint;
                      c2 = bPoint;
                  } else {
                      c1 = bPoint;
                      c2 = aPoint;
                  }
  
                  // One contribution is a permutation of (1,1,-1)
                  if ((c1 & 0x01) == 0) {
                      dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_3D;
                      dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D;
                      dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D;
                      xsv_ext0 = xsb - 1;
                      ysv_ext0 = ysb + 1;
                      zsv_ext0 = zsb + 1;
                  } else if ((c1 & 0x02) == 0) {
                      dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D;
                      dy_ext0 = dy0 + 1 - SQUISH_CONSTANT_3D;
                      dz_ext0 = dz0 - 1 - SQUISH_CONSTANT_3D;
                      xsv_ext0 = xsb + 1;
                      ysv_ext0 = ysb - 1;
                      zsv_ext0 = zsb + 1;
                  } else {
                      dx_ext0 = dx0 - 1 - SQUISH_CONSTANT_3D;
                      dy_ext0 = dy0 - 1 - SQUISH_CONSTANT_3D;
                      dz_ext0 = dz0 + 1 - SQUISH_CONSTANT_3D;
                      xsv_ext0 = xsb + 1;
                      ysv_ext0 = ysb + 1;
                      zsv_ext0 = zsb - 1;
                  }
  
                  // One contribution is a permutation of (0,0,2)
                  dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_3D;
                  dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_3D;
                  dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_3D;
                  xsv_ext1 = xsb;
                  ysv_ext1 = ysb;
                  zsv_ext1 = zsb;
                  if ((c2 & 0x01) != 0) {
                      dx_ext1 -= 2;
                      xsv_ext1 += 2;
                  } else if ((c2 & 0x02) != 0) {
                      dy_ext1 -= 2;
                      ysv_ext1 += 2;
                  } else {
                      dz_ext1 -= 2;
                      zsv_ext1 += 2;
                  }
              }
  
              // Contribution (1,0,0)
              double dx1 = dx0 - 1 - SQUISH_CONSTANT_3D;
              double dy1 = dy0 - 0 - SQUISH_CONSTANT_3D;
              double dz1 = dz0 - 0 - SQUISH_CONSTANT_3D;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, zsb + 0, dx1, dy1, dz1);
              }
  
              // Contribution (0,1,0)
              double dx2 = dx0 - 0 - SQUISH_CONSTANT_3D;
              double dy2 = dy0 - 1 - SQUISH_CONSTANT_3D;
              double dz2 = dz1;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, zsb + 0, dx2, dy2, dz2);
              }
  
              // Contribution (0,0,1)
              double dx3 = dx2;
              double dy3 = dy1;
              double dz3 = dz0 - 1 - SQUISH_CONSTANT_3D;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 0, ysb + 0, zsb + 1, dx3, dy3, dz3);
              }
  
              // Contribution (1,1,0)
              double dx4 = dx0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double dy4 = dy0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double dz4 = dz0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4;
              if (attn4 > 0) {
                  attn4 *= attn4;
                  value += attn4 * attn4 * extrapolate(xsb + 1, ysb + 1, zsb + 0, dx4, dy4, dz4);
              }
  
              // Contribution (1,0,1)
              double dx5 = dx4;
              double dy5 = dy0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double dz5 = dz0 - 1 - 2 * SQUISH_CONSTANT_3D;
              double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5;
              if (attn5 > 0) {
                  attn5 *= attn5;
                  value += attn5 * attn5 * extrapolate(xsb + 1, ysb + 0, zsb + 1, dx5, dy5, dz5);
              }
  
              // Contribution (0,1,1)
              double dx6 = dx0 - 0 - 2 * SQUISH_CONSTANT_3D;
              double dy6 = dy4;
              double dz6 = dz5;
              double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6;
              if (attn6 > 0) {
                  attn6 *= attn6;
                  value += attn6 * attn6 * extrapolate(xsb + 0, ysb + 1, zsb + 1, dx6, dy6, dz6);
              }
          }
  
          // First extra vertex
          double attn_ext0 = 2 - dx_ext0 * dx_ext0 - dy_ext0 * dy_ext0 - dz_ext0 * dz_ext0;
          if (attn_ext0 > 0) {
              attn_ext0 *= attn_ext0;
              value += attn_ext0 * attn_ext0 * extrapolate(xsv_ext0, ysv_ext0, zsv_ext0, dx_ext0, dy_ext0, dz_ext0);
          }
  
          // Second extra vertex
          double attn_ext1 = 2 - dx_ext1 * dx_ext1 - dy_ext1 * dy_ext1 - dz_ext1 * dz_ext1;
          if (attn_ext1 > 0) {
              attn_ext1 *= attn_ext1;
              value += attn_ext1 * attn_ext1 * extrapolate(xsv_ext1, ysv_ext1, zsv_ext1, dx_ext1, dy_ext1, dz_ext1);
          }
  
          return value / NORM_CONSTANT_3D;
      }
  
      // 4D OpenSimplex (Simplectic) Noise.
      public double eval(double x, double y, double z, double w) {
  
          // Place input coordinates on simplectic honeycomb.
          double stretchOffset = (x + y + z + w) * STRETCH_CONSTANT_4D;
          double xs = x + stretchOffset;
          double ys = y + stretchOffset;
          double zs = z + stretchOffset;
          double ws = w + stretchOffset;
  
          // Floor to get simplectic honeycomb coordinates of rhombo-hypercube super-cell origin.
          int xsb = fastFloor(xs);
          int ysb = fastFloor(ys);
          int zsb = fastFloor(zs);
          int wsb = fastFloor(ws);
  
          // Skew out to get actual coordinates of stretched rhombo-hypercube origin. We'll need these later.
          double squishOffset = (xsb + ysb + zsb + wsb) * SQUISH_CONSTANT_4D;
          double xb = xsb + squishOffset;
          double yb = ysb + squishOffset;
          double zb = zsb + squishOffset;
          double wb = wsb + squishOffset;
  
          // Compute simplectic honeycomb coordinates relative to rhombo-hypercube origin.
          double xins = xs - xsb;
          double yins = ys - ysb;
          double zins = zs - zsb;
          double wins = ws - wsb;
  
          // Sum those together to get a value that determines which region we're in.
          double inSum = xins + yins + zins + wins;
  
          // Positions relative to origin point.
          double dx0 = x - xb;
          double dy0 = y - yb;
          double dz0 = z - zb;
          double dw0 = w - wb;
  
          // We'll be defining these inside the next block and using them afterwards.
          double dx_ext0, dy_ext0, dz_ext0, dw_ext0;
          double dx_ext1, dy_ext1, dz_ext1, dw_ext1;
          double dx_ext2, dy_ext2, dz_ext2, dw_ext2;
          int xsv_ext0, ysv_ext0, zsv_ext0, wsv_ext0;
          int xsv_ext1, ysv_ext1, zsv_ext1, wsv_ext1;
          int xsv_ext2, ysv_ext2, zsv_ext2, wsv_ext2;
  
          double value = 0;
          if (inSum <= 1) { // We're inside the pentachoron (4-Simplex) at (0,0,0,0)
  
              // Determine which two of (0,0,0,1), (0,0,1,0), (0,1,0,0), (1,0,0,0) are closest.
              byte aPoint = 0x01;
              double aScore = xins;
              byte bPoint = 0x02;
              double bScore = yins;
              if (aScore >= bScore && zins > bScore) {
                  bScore = zins;
                  bPoint = 0x04;
              } else if (aScore < bScore && zins > aScore) {
                  aScore = zins;
                  aPoint = 0x04;
              }
              if (aScore >= bScore && wins > bScore) {
                  bScore = wins;
                  bPoint = 0x08;
              } else if (aScore < bScore && wins > aScore) {
                  aScore = wins;
                  aPoint = 0x08;
              }
  
              // Now we determine the three lattice points not part of the pentachoron that may contribute.
              // This depends on the closest two pentachoron vertices, including (0,0,0,0)
              double uins = 1 - inSum;
              if (uins > aScore || uins > bScore) { // (0,0,0,0) is one of the closest two pentachoron vertices.
                  byte c = (bScore > aScore ? bPoint : aPoint); // Our other closest vertex is the closest out of a and b.
                  if ((c & 0x01) == 0) {
                      xsv_ext0 = xsb - 1;
                      xsv_ext1 = xsv_ext2 = xsb;
                      dx_ext0 = dx0 + 1;
                      dx_ext1 = dx_ext2 = dx0;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb + 1;
                      dx_ext0 = dx_ext1 = dx_ext2 = dx0 - 1;
                  }
  
                  if ((c & 0x02) == 0) {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb;
                      dy_ext0 = dy_ext1 = dy_ext2 = dy0;
                      if ((c & 0x01) == 0x01) {
                          ysv_ext0 -= 1;
                          dy_ext0 += 1;
                      } else {
                          ysv_ext1 -= 1;
                          dy_ext1 += 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 1;
                  }
  
                  if ((c & 0x04) == 0) {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb;
                      dz_ext0 = dz_ext1 = dz_ext2 = dz0;
                      if ((c & 0x03) != 0) {
                          if ((c & 0x03) == 0x03) {
                              zsv_ext0 -= 1;
                              dz_ext0 += 1;
                          } else {
                              zsv_ext1 -= 1;
                              dz_ext1 += 1;
                          }
                      } else {
                          zsv_ext2 -= 1;
                          dz_ext2 += 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1;
                      dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 1;
                  }
  
                  if ((c & 0x08) == 0) {
                      wsv_ext0 = wsv_ext1 = wsb;
                      wsv_ext2 = wsb - 1;
                      dw_ext0 = dw_ext1 = dw0;
                      dw_ext2 = dw0 + 1;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb + 1;
                      dw_ext0 = dw_ext1 = dw_ext2 = dw0 - 1;
                  }
              } else { // (0,0,0,0) is not one of the closest two pentachoron vertices.
                  byte c = (byte) (aPoint | bPoint); // Our three extra vertices are determined by the closest two.
  
                  if ((c & 0x01) == 0) {
                      xsv_ext0 = xsv_ext2 = xsb;
                      xsv_ext1 = xsb - 1;
                      dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx0 + 1 - SQUISH_CONSTANT_4D;
                      dx_ext2 = dx0 - SQUISH_CONSTANT_4D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb + 1;
                      dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx_ext2 = dx0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x02) == 0) {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb;
                      dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext1 = dy_ext2 = dy0 - SQUISH_CONSTANT_4D;
                      if ((c & 0x01) == 0x01) {
                          ysv_ext1 -= 1;
                          dy_ext1 += 1;
                      } else {
                          ysv_ext2 -= 1;
                          dy_ext2 += 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1;
                      dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext1 = dy_ext2 = dy0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x04) == 0) {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb;
                      dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext1 = dz_ext2 = dz0 - SQUISH_CONSTANT_4D;
                      if ((c & 0x03) == 0x03) {
                          zsv_ext1 -= 1;
                          dz_ext1 += 1;
                      } else {
                          zsv_ext2 -= 1;
                          dz_ext2 += 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1;
                      dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext1 = dz_ext2 = dz0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x08) == 0) {
                      wsv_ext0 = wsv_ext1 = wsb;
                      wsv_ext2 = wsb - 1;
                      dw_ext0 = dw0 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw0 - SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 + 1 - SQUISH_CONSTANT_4D;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb + 1;
                      dw_ext0 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw_ext2 = dw0 - 1 - SQUISH_CONSTANT_4D;
                  }
              }
  
              // Contribution (0,0,0,0)
              double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0 - dw0 * dw0;
              if (attn0 > 0) {
                  attn0 *= attn0;
                  value += attn0 * attn0 * extrapolate(xsb + 0, ysb + 0, zsb + 0, wsb + 0, dx0, dy0, dz0, dw0);
              }
  
              // Contribution (1,0,0,0)
              double dx1 = dx0 - 1 - SQUISH_CONSTANT_4D;
              double dy1 = dy0 - 0 - SQUISH_CONSTANT_4D;
              double dz1 = dz0 - 0 - SQUISH_CONSTANT_4D;
              double dw1 = dw0 - 0 - SQUISH_CONSTANT_4D;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, zsb + 0, wsb + 0, dx1, dy1, dz1, dw1);
              }
  
              // Contribution (0,1,0,0)
              double dx2 = dx0 - 0 - SQUISH_CONSTANT_4D;
              double dy2 = dy0 - 1 - SQUISH_CONSTANT_4D;
              double dz2 = dz1;
              double dw2 = dw1;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, zsb + 0, wsb + 0, dx2, dy2, dz2, dw2);
              }
  
              // Contribution (0,0,1,0)
              double dx3 = dx2;
              double dy3 = dy1;
              double dz3 = dz0 - 1 - SQUISH_CONSTANT_4D;
              double dw3 = dw1;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 0, ysb + 0, zsb + 1, wsb + 0, dx3, dy3, dz3, dw3);
              }
  
              // Contribution (0,0,0,1)
              double dx4 = dx2;
              double dy4 = dy1;
              double dz4 = dz1;
              double dw4 = dw0 - 1 - SQUISH_CONSTANT_4D;
              double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4;
              if (attn4 > 0) {
                  attn4 *= attn4;
                  value += attn4 * attn4 * extrapolate(xsb + 0, ysb + 0, zsb + 0, wsb + 1, dx4, dy4, dz4, dw4);
              }
          } else if (inSum >= 3) { // We're inside the pentachoron (4-Simplex) at (1,1,1,1)
              // Determine which two of (1,1,1,0), (1,1,0,1), (1,0,1,1), (0,1,1,1) are closest.
              byte aPoint = 0x0E;
              double aScore = xins;
              byte bPoint = 0x0D;
              double bScore = yins;
              if (aScore <= bScore && zins < bScore) {
                  bScore = zins;
                  bPoint = 0x0B;
              } else if (aScore > bScore && zins < aScore) {
                  aScore = zins;
                  aPoint = 0x0B;
              }
              if (aScore <= bScore && wins < bScore) {
                  bScore = wins;
                  bPoint = 0x07;
              } else if (aScore > bScore && wins < aScore) {
                  aScore = wins;
                  aPoint = 0x07;
              }
  
              // Now we determine the three lattice points not part of the pentachoron that may contribute.
              // This depends on the closest two pentachoron vertices, including (0,0,0,0)
              double uins = 4 - inSum;
              if (uins < aScore || uins < bScore) { // (1,1,1,1) is one of the closest two pentachoron vertices.
                  byte c = (bScore < aScore ? bPoint : aPoint); // Our other closest vertex is the closest out of a and b.
  
                  if ((c & 0x01) != 0) {
                      xsv_ext0 = xsb + 2;
                      xsv_ext1 = xsv_ext2 = xsb + 1;
                      dx_ext0 = dx0 - 2 - 4 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx_ext2 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb;
                      dx_ext0 = dx_ext1 = dx_ext2 = dx0 - 4 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x02) != 0) {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      if ((c & 0x01) != 0) {
                          ysv_ext1 += 1;
                          dy_ext1 -= 1;
                      } else {
                          ysv_ext0 += 1;
                          dy_ext0 -= 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb;
                      dy_ext0 = dy_ext1 = dy_ext2 = dy0 - 4 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x04) != 0) {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1;
                      dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      if ((c & 0x03) != 0x03) {
                          if ((c & 0x03) == 0) {
                              zsv_ext0 += 1;
                              dz_ext0 -= 1;
                          } else {
                              zsv_ext1 += 1;
                              dz_ext1 -= 1;
                          }
                      } else {
                          zsv_ext2 += 1;
                          dz_ext2 -= 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb;
                      dz_ext0 = dz_ext1 = dz_ext2 = dz0 - 4 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x08) != 0) {
                      wsv_ext0 = wsv_ext1 = wsb + 1;
                      wsv_ext2 = wsb + 2;
                      dw_ext0 = dw_ext1 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 - 2 - 4 * SQUISH_CONSTANT_4D;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb;
                      dw_ext0 = dw_ext1 = dw_ext2 = dw0 - 4 * SQUISH_CONSTANT_4D;
                  }
              } else { // (1,1,1,1) is not one of the closest two pentachoron vertices.
                  byte c = (byte) (aPoint & bPoint); // Our three extra vertices are determined by the closest two.
  
                  if ((c & 0x01) != 0) {
                      xsv_ext0 = xsv_ext2 = xsb + 1;
                      xsv_ext1 = xsb + 2;
                      dx_ext0 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D;
                      dx_ext2 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsv_ext2 = xsb;
                      dx_ext0 = dx0 - 2 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx_ext2 = dx0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x02) != 0) {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb + 1;
                      dy_ext0 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext1 = dy_ext2 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      if ((c & 0x01) != 0) {
                          ysv_ext2 += 1;
                          dy_ext2 -= 1;
                      } else {
                          ysv_ext1 += 1;
                          dy_ext1 -= 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysv_ext2 = ysb;
                      dy_ext0 = dy0 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext1 = dy_ext2 = dy0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x04) != 0) {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb + 1;
                      dz_ext0 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext1 = dz_ext2 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      if ((c & 0x03) != 0) {
                          zsv_ext2 += 1;
                          dz_ext2 -= 1;
                      } else {
                          zsv_ext1 += 1;
                          dz_ext1 -= 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsv_ext2 = zsb;
                      dz_ext0 = dz0 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext1 = dz_ext2 = dz0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c & 0x08) != 0) {
                      wsv_ext0 = wsv_ext1 = wsb + 1;
                      wsv_ext2 = wsb + 2;
                      dw_ext0 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsv_ext2 = wsb;
                      dw_ext0 = dw0 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw_ext2 = dw0 - 3 * SQUISH_CONSTANT_4D;
                  }
              }
  
              // Contribution (1,1,1,0)
              double dx4 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dy4 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dz4 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dw4 = dw0 - 3 * SQUISH_CONSTANT_4D;
              double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4;
              if (attn4 > 0) {
                  attn4 *= attn4;
                  value += attn4 * attn4 * extrapolate(xsb + 1, ysb + 1, zsb + 1, wsb + 0, dx4, dy4, dz4, dw4);
              }
  
              // Contribution (1,1,0,1)
              double dx3 = dx4;
              double dy3 = dy4;
              double dz3 = dz0 - 3 * SQUISH_CONSTANT_4D;
              double dw3 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 1, ysb + 1, zsb + 0, wsb + 1, dx3, dy3, dz3, dw3);
              }
  
              // Contribution (1,0,1,1)
              double dx2 = dx4;
              double dy2 = dy0 - 3 * SQUISH_CONSTANT_4D;
              double dz2 = dz4;
              double dw2 = dw3;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 1, ysb + 0, zsb + 1, wsb + 1, dx2, dy2, dz2, dw2);
              }
  
              // Contribution (0,1,1,1)
              double dx1 = dx0 - 3 * SQUISH_CONSTANT_4D;
              double dz1 = dz4;
              double dy1 = dy4;
              double dw1 = dw3;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 0, ysb + 1, zsb + 1, wsb + 1, dx1, dy1, dz1, dw1);
              }
  
              // Contribution (1,1,1,1)
              dx0 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D;
              dy0 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D;
              dz0 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D;
              dw0 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D;
              double attn0 = 2 - dx0 * dx0 - dy0 * dy0 - dz0 * dz0 - dw0 * dw0;
              if (attn0 > 0) {
                  attn0 *= attn0;
                  value += attn0 * attn0 * extrapolate(xsb + 1, ysb + 1, zsb + 1, wsb + 1, dx0, dy0, dz0, dw0);
              }
          } else if (inSum <= 2) { // We're inside the first dispentachoron (Rectified 4-Simplex)
              double aScore;
              byte aPoint;
              boolean aIsBiggerSide = true;
              double bScore;
              byte bPoint;
              boolean bIsBiggerSide = true;
  
              // Decide between (1,1,0,0) and (0,0,1,1)
              if (xins + yins > zins + wins) {
                  aScore = xins + yins;
                  aPoint = 0x03;
              } else {
                  aScore = zins + wins;
                  aPoint = 0x0C;
              }
  
              // Decide between (1,0,1,0) and (0,1,0,1)
              if (xins + zins > yins + wins) {
                  bScore = xins + zins;
                  bPoint = 0x05;
              } else {
                  bScore = yins + wins;
                  bPoint = 0x0A;
              }
  
              // Closer between (1,0,0,1) and (0,1,1,0) will replace the further of a and b, if closer.
              if (xins + wins > yins + zins) {
                  double score = xins + wins;
                  if (aScore >= bScore && score > bScore) {
                      bScore = score;
                      bPoint = 0x09;
                  } else if (aScore < bScore && score > aScore) {
                      aScore = score;
                      aPoint = 0x09;
                  }
              } else {
                  double score = yins + zins;
                  if (aScore >= bScore && score > bScore) {
                      bScore = score;
                      bPoint = 0x06;
                  } else if (aScore < bScore && score > aScore) {
                      aScore = score;
                      aPoint = 0x06;
                  }
              }
  
              // Decide if (1,0,0,0) is closer.
              double p1 = 2 - inSum + xins;
              if (aScore >= bScore && p1 > bScore) {
                  bScore = p1;
                  bPoint = 0x01;
                  bIsBiggerSide = false;
              } else if (aScore < bScore && p1 > aScore) {
                  aScore = p1;
                  aPoint = 0x01;
                  aIsBiggerSide = false;
              }
  
              // Decide if (0,1,0,0) is closer.
              double p2 = 2 - inSum + yins;
              if (aScore >= bScore && p2 > bScore) {
                  bScore = p2;
                  bPoint = 0x02;
                  bIsBiggerSide = false;
              } else if (aScore < bScore && p2 > aScore) {
                  aScore = p2;
                  aPoint = 0x02;
                  aIsBiggerSide = false;
              }
  
              // Decide if (0,0,1,0) is closer.
              double p3 = 2 - inSum + zins;
              if (aScore >= bScore && p3 > bScore) {
                  bScore = p3;
                  bPoint = 0x04;
                  bIsBiggerSide = false;
              } else if (aScore < bScore && p3 > aScore) {
                  aScore = p3;
                  aPoint = 0x04;
                  aIsBiggerSide = false;
              }
  
              // Decide if (0,0,0,1) is closer.
              double p4 = 2 - inSum + wins;
              if (aScore >= bScore && p4 > bScore) {
                  bScore = p4;
                  bPoint = 0x08;
                  bIsBiggerSide = false;
              } else if (aScore < bScore && p4 > aScore) {
                  aScore = p4;
                  aPoint = 0x08;
                  aIsBiggerSide = false;
              }
  
              // Where each of the two closest points are determines how the extra three vertices are calculated.
              if (aIsBiggerSide == bIsBiggerSide) {
                  if (aIsBiggerSide) { // Both closest points on the bigger side
                      byte c1 = (byte) (aPoint | bPoint);
                      byte c2 = (byte) (aPoint & bPoint);
                      if ((c1 & 0x01) == 0) {
                          xsv_ext0 = xsb;
                          xsv_ext1 = xsb - 1;
                          dx_ext0 = dx0 - 3 * SQUISH_CONSTANT_4D;
                          dx_ext1 = dx0 + 1 - 2 * SQUISH_CONSTANT_4D;
                      } else {
                          xsv_ext0 = xsv_ext1 = xsb + 1;
                          dx_ext0 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          dx_ext1 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c1 & 0x02) == 0) {
                          ysv_ext0 = ysb;
                          ysv_ext1 = ysb - 1;
                          dy_ext0 = dy0 - 3 * SQUISH_CONSTANT_4D;
                          dy_ext1 = dy0 + 1 - 2 * SQUISH_CONSTANT_4D;
                      } else {
                          ysv_ext0 = ysv_ext1 = ysb + 1;
                          dy_ext0 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          dy_ext1 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c1 & 0x04) == 0) {
                          zsv_ext0 = zsb;
                          zsv_ext1 = zsb - 1;
                          dz_ext0 = dz0 - 3 * SQUISH_CONSTANT_4D;
                          dz_ext1 = dz0 + 1 - 2 * SQUISH_CONSTANT_4D;
                      } else {
                          zsv_ext0 = zsv_ext1 = zsb + 1;
                          dz_ext0 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          dz_ext1 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c1 & 0x08) == 0) {
                          wsv_ext0 = wsb;
                          wsv_ext1 = wsb - 1;
                          dw_ext0 = dw0 - 3 * SQUISH_CONSTANT_4D;
                          dw_ext1 = dw0 + 1 - 2 * SQUISH_CONSTANT_4D;
                      } else {
                          wsv_ext0 = wsv_ext1 = wsb + 1;
                          dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          dw_ext1 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      }
  
                      // One combination is a permutation of (0,0,0,2) based on c2
                      xsv_ext2 = xsb;
                      ysv_ext2 = ysb;
                      zsv_ext2 = zsb;
                      wsv_ext2 = wsb;
                      dx_ext2 = dx0 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext2 = dy0 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext2 = dz0 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 - 2 * SQUISH_CONSTANT_4D;
                      if ((c2 & 0x01) != 0) {
                          xsv_ext2 += 2;
                          dx_ext2 -= 2;
                      } else if ((c2 & 0x02) != 0) {
                          ysv_ext2 += 2;
                          dy_ext2 -= 2;
                      } else if ((c2 & 0x04) != 0) {
                          zsv_ext2 += 2;
                          dz_ext2 -= 2;
                      } else {
                          wsv_ext2 += 2;
                          dw_ext2 -= 2;
                      }
  
                  } else { // Both closest points on the smaller side
                      // One of the two extra points is (0,0,0,0)
                      xsv_ext2 = xsb;
                      ysv_ext2 = ysb;
                      zsv_ext2 = zsb;
                      wsv_ext2 = wsb;
                      dx_ext2 = dx0;
                      dy_ext2 = dy0;
                      dz_ext2 = dz0;
                      dw_ext2 = dw0;
  
                      // Other two points are based on the omitted axes.
                      byte c = (byte) (aPoint | bPoint);
  
                      if ((c & 0x01) == 0) {
                          xsv_ext0 = xsb - 1;
                          xsv_ext1 = xsb;
                          dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_4D;
                          dx_ext1 = dx0 - SQUISH_CONSTANT_4D;
                      } else {
                          xsv_ext0 = xsv_ext1 = xsb + 1;
                          dx_ext0 = dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x02) == 0) {
                          ysv_ext0 = ysv_ext1 = ysb;
                          dy_ext0 = dy_ext1 = dy0 - SQUISH_CONSTANT_4D;
                          if ((c & 0x01) == 0x01) {
                              ysv_ext0 -= 1;
                              dy_ext0 += 1;
                          } else {
                              ysv_ext1 -= 1;
                              dy_ext1 += 1;
                          }
                      } else {
                          ysv_ext0 = ysv_ext1 = ysb + 1;
                          dy_ext0 = dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x04) == 0) {
                          zsv_ext0 = zsv_ext1 = zsb;
                          dz_ext0 = dz_ext1 = dz0 - SQUISH_CONSTANT_4D;
                          if ((c & 0x03) == 0x03) {
                              zsv_ext0 -= 1;
                              dz_ext0 += 1;
                          } else {
                              zsv_ext1 -= 1;
                              dz_ext1 += 1;
                          }
                      } else {
                          zsv_ext0 = zsv_ext1 = zsb + 1;
                          dz_ext0 = dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x08) == 0) {
                          wsv_ext0 = wsb;
                          wsv_ext1 = wsb - 1;
                          dw_ext0 = dw0 - SQUISH_CONSTANT_4D;
                          dw_ext1 = dw0 + 1 - SQUISH_CONSTANT_4D;
                      } else {
                          wsv_ext0 = wsv_ext1 = wsb + 1;
                          dw_ext0 = dw_ext1 = dw0 - 1 - SQUISH_CONSTANT_4D;
                      }
  
                  }
              } else { // One point on each "side"
                  byte c1, c2;
                  if (aIsBiggerSide) {
                      c1 = aPoint;
                      c2 = bPoint;
                  } else {
                      c1 = bPoint;
                      c2 = aPoint;
                  }
  
                  // Two contributions are the bigger-sided point with each 0 replaced with -1.
                  if ((c1 & 0x01) == 0) {
                      xsv_ext0 = xsb - 1;
                      xsv_ext1 = xsb;
                      dx_ext0 = dx0 + 1 - SQUISH_CONSTANT_4D;
                      dx_ext1 = dx0 - SQUISH_CONSTANT_4D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb + 1;
                      dx_ext0 = dx_ext1 = dx0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x02) == 0) {
                      ysv_ext0 = ysv_ext1 = ysb;
                      dy_ext0 = dy_ext1 = dy0 - SQUISH_CONSTANT_4D;
                      if ((c1 & 0x01) == 0x01) {
                          ysv_ext0 -= 1;
                          dy_ext0 += 1;
                      } else {
                          ysv_ext1 -= 1;
                          dy_ext1 += 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x04) == 0) {
                      zsv_ext0 = zsv_ext1 = zsb;
                      dz_ext0 = dz_ext1 = dz0 - SQUISH_CONSTANT_4D;
                      if ((c1 & 0x03) == 0x03) {
                          zsv_ext0 -= 1;
                          dz_ext0 += 1;
                      } else {
                          zsv_ext1 -= 1;
                          dz_ext1 += 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb + 1;
                      dz_ext0 = dz_ext1 = dz0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x08) == 0) {
                      wsv_ext0 = wsb;
                      wsv_ext1 = wsb - 1;
                      dw_ext0 = dw0 - SQUISH_CONSTANT_4D;
                      dw_ext1 = dw0 + 1 - SQUISH_CONSTANT_4D;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsb + 1;
                      dw_ext0 = dw_ext1 = dw0 - 1 - SQUISH_CONSTANT_4D;
                  }
  
                  // One contribution is a permutation of (0,0,0,2) based on the smaller-sided point
                  xsv_ext2 = xsb;
                  ysv_ext2 = ysb;
                  zsv_ext2 = zsb;
                  wsv_ext2 = wsb;
                  dx_ext2 = dx0 - 2 * SQUISH_CONSTANT_4D;
                  dy_ext2 = dy0 - 2 * SQUISH_CONSTANT_4D;
                  dz_ext2 = dz0 - 2 * SQUISH_CONSTANT_4D;
                  dw_ext2 = dw0 - 2 * SQUISH_CONSTANT_4D;
                  if ((c2 & 0x01) != 0) {
                      xsv_ext2 += 2;
                      dx_ext2 -= 2;
                  } else if ((c2 & 0x02) != 0) {
                      ysv_ext2 += 2;
                      dy_ext2 -= 2;
                  } else if ((c2 & 0x04) != 0) {
                      zsv_ext2 += 2;
                      dz_ext2 -= 2;
                  } else {
                      wsv_ext2 += 2;
                      dw_ext2 -= 2;
                  }
              }
  
              // Contribution (1,0,0,0)
              double dx1 = dx0 - 1 - SQUISH_CONSTANT_4D;
              double dy1 = dy0 - 0 - SQUISH_CONSTANT_4D;
              double dz1 = dz0 - 0 - SQUISH_CONSTANT_4D;
              double dw1 = dw0 - 0 - SQUISH_CONSTANT_4D;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 1, ysb + 0, zsb + 0, wsb + 0, dx1, dy1, dz1, dw1);
              }
  
              // Contribution (0,1,0,0)
              double dx2 = dx0 - 0 - SQUISH_CONSTANT_4D;
              double dy2 = dy0 - 1 - SQUISH_CONSTANT_4D;
              double dz2 = dz1;
              double dw2 = dw1;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 0, ysb + 1, zsb + 0, wsb + 0, dx2, dy2, dz2, dw2);
              }
  
              // Contribution (0,0,1,0)
              double dx3 = dx2;
              double dy3 = dy1;
              double dz3 = dz0 - 1 - SQUISH_CONSTANT_4D;
              double dw3 = dw1;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 0, ysb + 0, zsb + 1, wsb + 0, dx3, dy3, dz3, dw3);
              }
  
              // Contribution (0,0,0,1)
              double dx4 = dx2;
              double dy4 = dy1;
              double dz4 = dz1;
              double dw4 = dw0 - 1 - SQUISH_CONSTANT_4D;
              double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4;
              if (attn4 > 0) {
                  attn4 *= attn4;
                  value += attn4 * attn4 * extrapolate(xsb + 0, ysb + 0, zsb + 0, wsb + 1, dx4, dy4, dz4, dw4);
              }
  
              // Contribution (1,1,0,0)
              double dx5 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy5 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz5 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw5 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5 - dw5 * dw5;
              if (attn5 > 0) {
                  attn5 *= attn5;
                  value += attn5 * attn5 * extrapolate(xsb + 1, ysb + 1, zsb + 0, wsb + 0, dx5, dy5, dz5, dw5);
              }
  
              // Contribution (1,0,1,0)
              double dx6 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy6 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz6 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw6 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6 - dw6 * dw6;
              if (attn6 > 0) {
                  attn6 *= attn6;
                  value += attn6 * attn6 * extrapolate(xsb + 1, ysb + 0, zsb + 1, wsb + 0, dx6, dy6, dz6, dw6);
              }
  
              // Contribution (1,0,0,1)
              double dx7 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy7 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz7 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw7 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn7 = 2 - dx7 * dx7 - dy7 * dy7 - dz7 * dz7 - dw7 * dw7;
              if (attn7 > 0) {
                  attn7 *= attn7;
                  value += attn7 * attn7 * extrapolate(xsb + 1, ysb + 0, zsb + 0, wsb + 1, dx7, dy7, dz7, dw7);
              }
  
              // Contribution (0,1,1,0)
              double dx8 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy8 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz8 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw8 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn8 = 2 - dx8 * dx8 - dy8 * dy8 - dz8 * dz8 - dw8 * dw8;
              if (attn8 > 0) {
                  attn8 *= attn8;
                  value += attn8 * attn8 * extrapolate(xsb + 0, ysb + 1, zsb + 1, wsb + 0, dx8, dy8, dz8, dw8);
              }
  
              // Contribution (0,1,0,1)
              double dx9 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy9 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz9 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw9 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn9 = 2 - dx9 * dx9 - dy9 * dy9 - dz9 * dz9 - dw9 * dw9;
              if (attn9 > 0) {
                  attn9 *= attn9;
                  value += attn9 * attn9 * extrapolate(xsb + 0, ysb + 1, zsb + 0, wsb + 1, dx9, dy9, dz9, dw9);
              }
  
              // Contribution (0,0,1,1)
              double dx10 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy10 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz10 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw10 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn10 = 2 - dx10 * dx10 - dy10 * dy10 - dz10 * dz10 - dw10 * dw10;
              if (attn10 > 0) {
                  attn10 *= attn10;
                  value += attn10 * attn10 * extrapolate(xsb + 0, ysb + 0, zsb + 1, wsb + 1, dx10, dy10, dz10, dw10);
              }
          } else { // We're inside the second dispentachoron (Rectified 4-Simplex)
              double aScore;
              byte aPoint;
              boolean aIsBiggerSide = true;
              double bScore;
              byte bPoint;
              boolean bIsBiggerSide = true;
  
              // Decide between (0,0,1,1) and (1,1,0,0)
              if (xins + yins < zins + wins) {
                  aScore = xins + yins;
                  aPoint = 0x0C;
              } else {
                  aScore = zins + wins;
                  aPoint = 0x03;
              }
  
              // Decide between (0,1,0,1) and (1,0,1,0)
              if (xins + zins < yins + wins) {
                  bScore = xins + zins;
                  bPoint = 0x0A;
              } else {
                  bScore = yins + wins;
                  bPoint = 0x05;
              }
  
              // Closer between (0,1,1,0) and (1,0,0,1) will replace the further of a and b, if closer.
              if (xins + wins < yins + zins) {
                  double score = xins + wins;
                  if (aScore <= bScore && score < bScore) {
                      bScore = score;
                      bPoint = 0x06;
                  } else if (aScore > bScore && score < aScore) {
                      aScore = score;
                      aPoint = 0x06;
                  }
              } else {
                  double score = yins + zins;
                  if (aScore <= bScore && score < bScore) {
                      bScore = score;
                      bPoint = 0x09;
                  } else if (aScore > bScore && score < aScore) {
                      aScore = score;
                      aPoint = 0x09;
                  }
              }
  
              // Decide if (0,1,1,1) is closer.
              double p1 = 3 - inSum + xins;
              if (aScore <= bScore && p1 < bScore) {
                  bScore = p1;
                  bPoint = 0x0E;
                  bIsBiggerSide = false;
              } else if (aScore > bScore && p1 < aScore) {
                  aScore = p1;
                  aPoint = 0x0E;
                  aIsBiggerSide = false;
              }
  
              // Decide if (1,0,1,1) is closer.
              double p2 = 3 - inSum + yins;
              if (aScore <= bScore && p2 < bScore) {
                  bScore = p2;
                  bPoint = 0x0D;
                  bIsBiggerSide = false;
              } else if (aScore > bScore && p2 < aScore) {
                  aScore = p2;
                  aPoint = 0x0D;
                  aIsBiggerSide = false;
              }
  
              // Decide if (1,1,0,1) is closer.
              double p3 = 3 - inSum + zins;
              if (aScore <= bScore && p3 < bScore) {
                  bScore = p3;
                  bPoint = 0x0B;
                  bIsBiggerSide = false;
              } else if (aScore > bScore && p3 < aScore) {
                  aScore = p3;
                  aPoint = 0x0B;
                  aIsBiggerSide = false;
              }
  
              // Decide if (1,1,1,0) is closer.
              double p4 = 3 - inSum + wins;
              if (aScore <= bScore && p4 < bScore) {
                  bScore = p4;
                  bPoint = 0x07;
                  bIsBiggerSide = false;
              } else if (aScore > bScore && p4 < aScore) {
                  aScore = p4;
                  aPoint = 0x07;
                  aIsBiggerSide = false;
              }
  
              // Where each of the two closest points are determines how the extra three vertices are calculated.
              if (aIsBiggerSide == bIsBiggerSide) {
                  if (aIsBiggerSide) { // Both closest points on the bigger side
                      byte c1 = (byte) (aPoint & bPoint);
                      byte c2 = (byte) (aPoint | bPoint);
  
                      // Two contributions are permutations of (0,0,0,1) and (0,0,0,2) based on c1
                      xsv_ext0 = xsv_ext1 = xsb;
                      ysv_ext0 = ysv_ext1 = ysb;
                      zsv_ext0 = zsv_ext1 = zsb;
                      wsv_ext0 = wsv_ext1 = wsb;
                      dx_ext0 = dx0 - SQUISH_CONSTANT_4D;
                      dy_ext0 = dy0 - SQUISH_CONSTANT_4D;
                      dz_ext0 = dz0 - SQUISH_CONSTANT_4D;
                      dw_ext0 = dw0 - SQUISH_CONSTANT_4D;
                      dx_ext1 = dx0 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext1 = dy0 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext1 = dz0 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw0 - 2 * SQUISH_CONSTANT_4D;
                      if ((c1 & 0x01) != 0) {
                          xsv_ext0 += 1;
                          dx_ext0 -= 1;
                          xsv_ext1 += 2;
                          dx_ext1 -= 2;
                      } else if ((c1 & 0x02) != 0) {
                          ysv_ext0 += 1;
                          dy_ext0 -= 1;
                          ysv_ext1 += 2;
                          dy_ext1 -= 2;
                      } else if ((c1 & 0x04) != 0) {
                          zsv_ext0 += 1;
                          dz_ext0 -= 1;
                          zsv_ext1 += 2;
                          dz_ext1 -= 2;
                      } else {
                          wsv_ext0 += 1;
                          dw_ext0 -= 1;
                          wsv_ext1 += 2;
                          dw_ext1 -= 2;
                      }
  
                      // One contribution is a permutation of (1,1,1,-1) based on c2
                      xsv_ext2 = xsb + 1;
                      ysv_ext2 = ysb + 1;
                      zsv_ext2 = zsb + 1;
                      wsv_ext2 = wsb + 1;
                      dx_ext2 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dy_ext2 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dz_ext2 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
                      if ((c2 & 0x01) == 0) {
                          xsv_ext2 -= 2;
                          dx_ext2 += 2;
                      } else if ((c2 & 0x02) == 0) {
                          ysv_ext2 -= 2;
                          dy_ext2 += 2;
                      } else if ((c2 & 0x04) == 0) {
                          zsv_ext2 -= 2;
                          dz_ext2 += 2;
                      } else {
                          wsv_ext2 -= 2;
                          dw_ext2 += 2;
                      }
                  } else { // Both closest points on the smaller side
                      // One of the two extra points is (1,1,1,1)
                      xsv_ext2 = xsb + 1;
                      ysv_ext2 = ysb + 1;
                      zsv_ext2 = zsb + 1;
                      wsv_ext2 = wsb + 1;
                      dx_ext2 = dx0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      dy_ext2 = dy0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      dz_ext2 = dz0 - 1 - 4 * SQUISH_CONSTANT_4D;
                      dw_ext2 = dw0 - 1 - 4 * SQUISH_CONSTANT_4D;
  
                      // Other two points are based on the shared axes.
                      byte c = (byte) (aPoint & bPoint);
  
                      if ((c & 0x01) != 0) {
                          xsv_ext0 = xsb + 2;
                          xsv_ext1 = xsb + 1;
                          dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D;
                          dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      } else {
                          xsv_ext0 = xsv_ext1 = xsb;
                          dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x02) != 0) {
                          ysv_ext0 = ysv_ext1 = ysb + 1;
                          dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          if ((c & 0x01) == 0) {
                              ysv_ext0 += 1;
                              dy_ext0 -= 1;
                          } else {
                              ysv_ext1 += 1;
                              dy_ext1 -= 1;
                          }
                      } else {
                          ysv_ext0 = ysv_ext1 = ysb;
                          dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x04) != 0) {
                          zsv_ext0 = zsv_ext1 = zsb + 1;
                          dz_ext0 = dz_ext1 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          if ((c & 0x03) == 0) {
                              zsv_ext0 += 1;
                              dz_ext0 -= 1;
                          } else {
                              zsv_ext1 += 1;
                              dz_ext1 -= 1;
                          }
                      } else {
                          zsv_ext0 = zsv_ext1 = zsb;
                          dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_4D;
                      }
  
                      if ((c & 0x08) != 0) {
                          wsv_ext0 = wsb + 1;
                          wsv_ext1 = wsb + 2;
                          dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
                          dw_ext1 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D;
                      } else {
                          wsv_ext0 = wsv_ext1 = wsb;
                          dw_ext0 = dw_ext1 = dw0 - 3 * SQUISH_CONSTANT_4D;
                      }
                  }
              } else { // One point on each "side"
                  byte c1, c2;
                  if (aIsBiggerSide) {
                      c1 = aPoint;
                      c2 = bPoint;
                  } else {
                      c1 = bPoint;
                      c2 = aPoint;
                  }
  
                  // Two contributions are the bigger-sided point with each 1 replaced with 2.
                  if ((c1 & 0x01) != 0) {
                      xsv_ext0 = xsb + 2;
                      xsv_ext1 = xsb + 1;
                      dx_ext0 = dx0 - 2 - 3 * SQUISH_CONSTANT_4D;
                      dx_ext1 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
                  } else {
                      xsv_ext0 = xsv_ext1 = xsb;
                      dx_ext0 = dx_ext1 = dx0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x02) != 0) {
                      ysv_ext0 = ysv_ext1 = ysb + 1;
                      dy_ext0 = dy_ext1 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      if ((c1 & 0x01) == 0) {
                          ysv_ext0 += 1;
                          dy_ext0 -= 1;
                      } else {
                          ysv_ext1 += 1;
                          dy_ext1 -= 1;
                      }
                  } else {
                      ysv_ext0 = ysv_ext1 = ysb;
                      dy_ext0 = dy_ext1 = dy0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x04) != 0) {
                      zsv_ext0 = zsv_ext1 = zsb + 1;
                      dz_ext0 = dz_ext1 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      if ((c1 & 0x03) == 0) {
                          zsv_ext0 += 1;
                          dz_ext0 -= 1;
                      } else {
                          zsv_ext1 += 1;
                          dz_ext1 -= 1;
                      }
                  } else {
                      zsv_ext0 = zsv_ext1 = zsb;
                      dz_ext0 = dz_ext1 = dz0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  if ((c1 & 0x08) != 0) {
                      wsv_ext0 = wsb + 1;
                      wsv_ext1 = wsb + 2;
                      dw_ext0 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
                      dw_ext1 = dw0 - 2 - 3 * SQUISH_CONSTANT_4D;
                  } else {
                      wsv_ext0 = wsv_ext1 = wsb;
                      dw_ext0 = dw_ext1 = dw0 - 3 * SQUISH_CONSTANT_4D;
                  }
  
                  // One contribution is a permutation of (1,1,1,-1) based on the smaller-sided point
                  xsv_ext2 = xsb + 1;
                  ysv_ext2 = ysb + 1;
                  zsv_ext2 = zsb + 1;
                  wsv_ext2 = wsb + 1;
                  dx_ext2 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
                  dy_ext2 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
                  dz_ext2 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
                  dw_ext2 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
                  if ((c2 & 0x01) == 0) {
                      xsv_ext2 -= 2;
                      dx_ext2 += 2;
                  } else if ((c2 & 0x02) == 0) {
                      ysv_ext2 -= 2;
                      dy_ext2 += 2;
                  } else if ((c2 & 0x04) == 0) {
                      zsv_ext2 -= 2;
                      dz_ext2 += 2;
                  } else {
                      wsv_ext2 -= 2;
                      dw_ext2 += 2;
                  }
              }
  
              // Contribution (1,1,1,0)
              double dx4 = dx0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dy4 = dy0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dz4 = dz0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double dw4 = dw0 - 3 * SQUISH_CONSTANT_4D;
              double attn4 = 2 - dx4 * dx4 - dy4 * dy4 - dz4 * dz4 - dw4 * dw4;
              if (attn4 > 0) {
                  attn4 *= attn4;
                  value += attn4 * attn4 * extrapolate(xsb + 1, ysb + 1, zsb + 1, wsb + 0, dx4, dy4, dz4, dw4);
              }
  
              // Contribution (1,1,0,1)
              double dx3 = dx4;
              double dy3 = dy4;
              double dz3 = dz0 - 3 * SQUISH_CONSTANT_4D;
              double dw3 = dw0 - 1 - 3 * SQUISH_CONSTANT_4D;
              double attn3 = 2 - dx3 * dx3 - dy3 * dy3 - dz3 * dz3 - dw3 * dw3;
              if (attn3 > 0) {
                  attn3 *= attn3;
                  value += attn3 * attn3 * extrapolate(xsb + 1, ysb + 1, zsb + 0, wsb + 1, dx3, dy3, dz3, dw3);
              }
  
              // Contribution (1,0,1,1)
              double dx2 = dx4;
              double dy2 = dy0 - 3 * SQUISH_CONSTANT_4D;
              double dz2 = dz4;
              double dw2 = dw3;
              double attn2 = 2 - dx2 * dx2 - dy2 * dy2 - dz2 * dz2 - dw2 * dw2;
              if (attn2 > 0) {
                  attn2 *= attn2;
                  value += attn2 * attn2 * extrapolate(xsb + 1, ysb + 0, zsb + 1, wsb + 1, dx2, dy2, dz2, dw2);
              }
  
              // Contribution (0,1,1,1)
              double dx1 = dx0 - 3 * SQUISH_CONSTANT_4D;
              double dz1 = dz4;
              double dy1 = dy4;
              double dw1 = dw3;
              double attn1 = 2 - dx1 * dx1 - dy1 * dy1 - dz1 * dz1 - dw1 * dw1;
              if (attn1 > 0) {
                  attn1 *= attn1;
                  value += attn1 * attn1 * extrapolate(xsb + 0, ysb + 1, zsb + 1, wsb + 1, dx1, dy1, dz1, dw1);
              }
  
              // Contribution (1,1,0,0)
              double dx5 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy5 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz5 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw5 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn5 = 2 - dx5 * dx5 - dy5 * dy5 - dz5 * dz5 - dw5 * dw5;
              if (attn5 > 0) {
                  attn5 *= attn5;
                  value += attn5 * attn5 * extrapolate(xsb + 1, ysb + 1, zsb + 0, wsb + 0, dx5, dy5, dz5, dw5);
              }
  
              // Contribution (1,0,1,0)
              double dx6 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy6 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz6 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw6 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn6 = 2 - dx6 * dx6 - dy6 * dy6 - dz6 * dz6 - dw6 * dw6;
              if (attn6 > 0) {
                  attn6 *= attn6;
                  value += attn6 * attn6 * extrapolate(xsb + 1, ysb + 0, zsb + 1, wsb + 0, dx6, dy6, dz6, dw6);
              }
  
              // Contribution (1,0,0,1)
              double dx7 = dx0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dy7 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz7 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw7 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn7 = 2 - dx7 * dx7 - dy7 * dy7 - dz7 * dz7 - dw7 * dw7;
              if (attn7 > 0) {
                  attn7 *= attn7;
                  value += attn7 * attn7 * extrapolate(xsb + 1, ysb + 0, zsb + 0, wsb + 1, dx7, dy7, dz7, dw7);
              }
  
              // Contribution (0,1,1,0)
              double dx8 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy8 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz8 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw8 = dw0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double attn8 = 2 - dx8 * dx8 - dy8 * dy8 - dz8 * dz8 - dw8 * dw8;
              if (attn8 > 0) {
                  attn8 *= attn8;
                  value += attn8 * attn8 * extrapolate(xsb + 0, ysb + 1, zsb + 1, wsb + 0, dx8, dy8, dz8, dw8);
              }
  
              // Contribution (0,1,0,1)
              double dx9 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy9 = dy0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dz9 = dz0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dw9 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn9 = 2 - dx9 * dx9 - dy9 * dy9 - dz9 * dz9 - dw9 * dw9;
              if (attn9 > 0) {
                  attn9 *= attn9;
                  value += attn9 * attn9 * extrapolate(xsb + 0, ysb + 1, zsb + 0, wsb + 1, dx9, dy9, dz9, dw9);
              }
  
              // Contribution (0,0,1,1)
              double dx10 = dx0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dy10 = dy0 - 0 - 2 * SQUISH_CONSTANT_4D;
              double dz10 = dz0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double dw10 = dw0 - 1 - 2 * SQUISH_CONSTANT_4D;
              double attn10 = 2 - dx10 * dx10 - dy10 * dy10 - dz10 * dz10 - dw10 * dw10;
              if (attn10 > 0) {
                  attn10 *= attn10;
                  value += attn10 * attn10 * extrapolate(xsb + 0, ysb + 0, zsb + 1, wsb + 1, dx10, dy10, dz10, dw10);
              }
          }
  
          // First extra vertex
          double attn_ext0 = 2 - dx_ext0 * dx_ext0 - dy_ext0 * dy_ext0 - dz_ext0 * dz_ext0 - dw_ext0 * dw_ext0;
          if (attn_ext0 > 0) {
              attn_ext0 *= attn_ext0;
              value += attn_ext0 * attn_ext0 * extrapolate(xsv_ext0, ysv_ext0, zsv_ext0, wsv_ext0, dx_ext0, dy_ext0, dz_ext0, dw_ext0);
          }
  
          // Second extra vertex
          double attn_ext1 = 2 - dx_ext1 * dx_ext1 - dy_ext1 * dy_ext1 - dz_ext1 * dz_ext1 - dw_ext1 * dw_ext1;
          if (attn_ext1 > 0) {
              attn_ext1 *= attn_ext1;
              value += attn_ext1 * attn_ext1 * extrapolate(xsv_ext1, ysv_ext1, zsv_ext1, wsv_ext1, dx_ext1, dy_ext1, dz_ext1, dw_ext1);
          }
  
          // Third extra vertex
          double attn_ext2 = 2 - dx_ext2 * dx_ext2 - dy_ext2 * dy_ext2 - dz_ext2 * dz_ext2 - dw_ext2 * dw_ext2;
          if (attn_ext2 > 0) {
              attn_ext2 *= attn_ext2;
              value += attn_ext2 * attn_ext2 * extrapolate(xsv_ext2, ysv_ext2, zsv_ext2, wsv_ext2, dx_ext2, dy_ext2, dz_ext2, dw_ext2);
          }
  
          return value / NORM_CONSTANT_4D;
      }
  
      private double extrapolate(int xsb, int ysb, double dx, double dy) {
          int index = perm[(perm[xsb & 0xFF] + ysb) & 0xFF] & 0x0E;
          return gradients2D[index] * dx + gradients2D[index + 1] * dy;
      }
  
      private double extrapolate(int xsb, int ysb, int zsb, double dx, double dy, double dz) {
          int index = permGradIndex3D[(perm[(perm[xsb & 0xFF] + ysb) & 0xFF] + zsb) & 0xFF];
          return gradients3D[index] * dx + gradients3D[index + 1] * dy + gradients3D[index + 2] * dz;
      }
  
      private double extrapolate(int xsb, int ysb, int zsb, int wsb, double dx, double dy, double dz, double dw) {
          int index = perm[(perm[(perm[(perm[xsb & 0xFF] + ysb) & 0xFF] + zsb) & 0xFF] + wsb) & 0xFF] & 0xFC;
          return gradients4D[index] * dx + gradients4D[index + 1] * dy + gradients4D[index + 2] * dz + gradients4D[index + 3] * dw;
      }
  
      private static int fastFloor(double x) {
          int xi = (int) x;
          return x < xi ? xi - 1 : xi;
      }
  
      // Gradients for 2D. They approximate the directions to the
      // vertices of an octagon from the center.
      private static byte[] gradients2D = new byte[] { 5, 2, 2, 5, -5, 2, -2, 5, 5, -2, 2, -5, -5, -2, -2, -5, };
  
      // Gradients for 3D. They approximate the directions to the
      // vertices of a rhombicuboctahedron from the center, skewed so
      // that the triangular and square facets can be inscribed inside
      // circles of the same radius.
      private static byte[] gradients3D = new byte[] { -11, 4, 4, -4, 11, 4, -4, 4, 11, 11, 4, 4, 4, 11, 4, 4, 4, 11, -11, -4, 4, -4, -11, 4, -4, -4, 11, 11, -4, 4, 4, -11, 4, 4, -4, 11, -11, 4, -4, -4, 11, -4, -4, 4, -11, 11, 4, -4, 4, 11, -4, 4, 4, -11, -11, -4, -4, -4, -11, -4, -4, -4, -11, 11, -4, -4, 4, -11, -4, 4, -4, -11, };
  
      // Gradients for 4D. They approximate the directions to the
      // vertices of a disprismatotesseractihexadecachoron from the center,
      // skewed so that the tetrahedral and cubic facets can be inscribed inside
      // spheres of the same radius.
      private static byte[] gradients4D = new byte[] { 3, 1, 1, 1, 1, 3, 1, 1, 1, 1, 3, 1, 1, 1, 1, 3, -3, 1, 1, 1, -1, 3, 1, 1, -1, 1, 3, 1, -1, 1, 1, 3, 3, -1, 1, 1, 1, -3, 1, 1, 1, -1, 3, 1, 1, -1, 1, 3, -3, -1, 1, 1, -1, -3, 1, 1, -1, -1, 3, 1, -1, -1, 1, 3, 3, 1, -1, 1, 1, 3, -1, 1, 1, 1, -3, 1, 1, 1, -1, 3, -3, 1, -1, 1, -1, 3, -1, 1, -1, 1, -3, 1, -1, 1, -1, 3, 3, -1, -1, 1, 1, -3, -1, 1, 1, -1, -3, 1, 1, -1, -1, 3, -3, -1, -1, 1, -1, -3, -1, 1, -1, -1, -3, 1, -1, -1, -1, 3, 3, 1, 1, -1, 1, 3, 1, -1, 1, 1, 3, -1, 1, 1, 1, -3, -3, 1, 1, -1, -1, 3, 1, -1, -1, 1, 3, -1, -1, 1, 1, -3, 3, -1, 1, -1, 1, -3, 1, -1, 1, -1, 3, -1, 1, -1, 1, -3, -3, -1, 1, -1, -1, -3, 1, -1, -1, -1, 3, -1, -1, -1, 1, -3, 3, 1, -1, -1, 1, 3, -1, -1, 1, 1, -3, -1, 1, 1, -1, -3, -3, 1, -1, -1, -1, 3, -1, -1, -1,
          1, -3, -1, -1, 1, -1, -3, 3, -1, -1, -1, 1, -3, -1, -1, 1, -1, -3, -1, 1, -1, -1, -3, -3, -1, -1, -1, -1, -3, -1, -1, -1, -1, -3, -1, -1, -1, -1, -3, };
  }
  