/// <summary>
/// See the documentation on the base class.
/// <seealso cref="Module"/>
/// </summary>
/// <param name="x">X coordinate</param>
/// <param name="y">Y coordinate</param>
/// <param name="z">Z coordinate</param>
/// <returns>Returns the computed value</returns>
public override double GetValue(double x, double y, double z)
{
var ix = NoiseMath.FastFloor(x);
var iy = NoiseMath.FastFloor(y);
var iz = NoiseMath.FastFloor(z);
return(((ix & 1) ^ (iy & 1) ^ (iz & 1)) != 0 ? -1.0 : 1.0);
}
// 3D simplex noise
public static double SimplexNoise3D(double xin, double yin, double zin)
{
// Skew the input space to determine which simplex cell we're in
// Very nice and simple skew factor for 3D
double s = (xin + yin + zin) * F3;
int i = NoiseMath.FastFloor(xin + s);
int j = NoiseMath.FastFloor(yin + s);
int k = NoiseMath.FastFloor(zin + s);
double t = (i + j + k) * G3;
// Unskew the cell origin back to (x,y,z) space
double X0 = i - t;
double Y0 = j - t;
double Z0 = k - t;
// The x,y,z distances from the cell origin
double x0 = xin - X0;
double y0 = yin - Y0;
double z0 = zin - Z0;
// For the 3D case, the simplex shape is a slightly irregular tetrahedron.
// Determine which simplex we are in.
int i1, j1, k1; // Offsets for second corner of simplex in (i,j,k) coords
int i2, j2, k2; // Offsets for third corner of simplex in (i,j,k) coords
if (x0 >= y0)
{
// X Y Z order
if (y0 >= z0)
{
i1 = 1;
j1 = 0;
k1 = 0;
i2 = 1;
j2 = 1;
k2 = 0;
}
// X Z Y order
else if (x0 >= z0)
{
i1 = 1;
j1 = 0;
k1 = 0;
i2 = 1;
j2 = 0;
k2 = 1;
}
// Z X Y order
else
{
i1 = 0;
j1 = 0;
k1 = 1;
i2 = 1;
j2 = 0;
k2 = 1;
}
}
else // x0<y0
{
// Z Y X order
if (y0 < z0)
{
i1 = 0;
j1 = 0;
k1 = 1;
i2 = 0;
j2 = 1;
k2 = 1;
}
// Y Z X order
else if (x0 < z0)
{
i1 = 0;
j1 = 1;
k1 = 0;
i2 = 0;
j2 = 1;
k2 = 1;
}
// Y X Z order
else
{
i1 = 0;
j1 = 1;
k1 = 0;
i2 = 1;
j2 = 1;
k2 = 0;
}
}
// A step of (1,0,0) in (i,j,k) means a step of (1-c,-c,-c) in (x,y,z),
// a step of (0,1,0) in (i,j,k) means a step of (-c,1-c,-c) in (x,y,z), and
// a step of (0,0,1) in (i,j,k) means a step of (-c,-c,1-c) in (x,y,z), where
// c = 1/6.
double x1 = x0 - i1 + G3; // Offsets for second corner in (x,y,z) coords
double y1 = y0 - j1 + G3;
double z1 = z0 - k1 + G3;
double x2 = x0 - i2 + 2.0 * G3; // Offsets for third corner in (x,y,z) coords
double y2 = y0 - j2 + 2.0 * G3;
double z2 = z0 - k2 + 2.0 * G3;
double x3 = x0 - 1.0 + 3.0 * G3; // Offsets for last corner in (x,y,z) coords
double y3 = y0 - 1.0 + 3.0 * G3;
double z3 = z0 - 1.0 + 3.0 * G3;
// Work out the hashed gradient indices of the four simplex corners
int ii = i & 255;
int jj = j & 255;
int kk = k & 255;
int gi0 = PermMod12[ii + Perm[jj + Perm[kk]]];
int gi1 = PermMod12[ii + i1 + Perm[jj + j1 + Perm[kk + k1]]];
int gi2 = PermMod12[ii + i2 + Perm[jj + j2 + Perm[kk + k2]]];
int gi3 = PermMod12[ii + 1 + Perm[jj + 1 + Perm[kk + 1]]];
// Noise contributions from the four corners
double n0 = 0.0, n1 = 0.0, n2 = 0.0, n3 = 0.0;
// Calculate the contribution from the four corners
double t0 = 0.6 - x0 * x0 - y0 * y0 - z0 * z0;
if (t0 >= 0)
{
t0 *= t0;
n0 = t0 * t0 * Dot(ref Grad3[gi0], x0, y0, z0);
}
double t1 = 0.6 - x1 * x1 - y1 * y1 - z1 * z1;
if (t1 >= 0)
{
t1 *= t1;
n1 = t1 * t1 * Dot(ref Grad3[gi1], x1, y1, z1);
}
double t2 = 0.6 - x2 * x2 - y2 * y2 - z2 * z2;
if (t2 >= 0)
{
t2 *= t2;
n2 = t2 * t2 * Dot(ref Grad3[gi2], x2, y2, z2);
}
double t3 = 0.6 - x3 * x3 - y3 * y3 - z3 * z3;
if (t3 >= 0)
{
t3 *= t3;
n3 = t3 * t3 * Dot(ref Grad3[gi3], x3, y3, z3);
}
// Add contributions from each corner to get the final noise value.
// The result is scaled to stay just inside [-1,1]
return(32.0 * (n0 + n1 + n2 + n3));
}
