/// <summary>
/// Generates a value-coherent-noise value from the coordinates of a
/// three-dimensional input value.
/// </summary>
/// <param name="x">The x coordinate of the input value.</param>
/// <param name="y">The y coordinate of the input value.</param>
/// <param name="z">The z coordinate of the input value.</param>
/// <param name="seed">The random number seed.</param>
/// <param name="noiseQuality">The quality of the coherent-noise.</param>
/// <returns>The generated value-coherent-noise value.</returns>
/// <remarks>
/// The return value ranges from -1.0 to +1.0.
///
/// For an explanation of the difference between gradient noise and
/// value noise, see the comments for the <see cref="GradientNoise3D"/> function.
/// </remarks>
public static double ValueCoherentNoise3D(double x, double y, double z, int seed = 0, NoiseQuality noiseQuality = NoiseQuality.Standard)
{
// Create a unit-length cube aligned along an integer boundary. This cube
// surrounds the input point.
var x0 = x > 0.0 ? (int)x : (int)x - 1;
var x1 = x0 + 1;
var y0 = y > 0.0 ? (int)y : (int)y - 1;
var y1 = y0 + 1;
var z0 = z > 0.0 ? (int)z : (int)z - 1;
var z1 = z0 + 1;
// Map the difference between the coordinates of the input value and the
// coordinates of the cube's outer-lower-left vertex onto an S-curve.
double xs = 0, ys = 0, zs = 0;
switch (noiseQuality)
{
case NoiseQuality.Fast:
xs = x - x0;
ys = y - y0;
zs = z - z0;
break;
case NoiseQuality.Standard:
xs = NoiseMath.SCurve3(x - x0);
ys = NoiseMath.SCurve3(y - y0);
zs = NoiseMath.SCurve3(z - z0);
break;
case NoiseQuality.Best:
xs = NoiseMath.SCurve5(x - x0);
ys = NoiseMath.SCurve5(y - y0);
zs = NoiseMath.SCurve5(z - z0);
break;
}
// Now calculate the noise values at each vertex of the cube. To generate
// the coherent-noise value at the input point, interpolate these eight
// noise values using the S-curve value as the interpolant (trilinear
// interpolation.)
double n0, n1, ix0, ix1, iy0, iy1;
n0 = ValueNoise3D(x0, y0, z0, seed);
n1 = ValueNoise3D(x1, y0, z0, seed);
ix0 = NoiseMath.Linear(n0, n1, xs);
n0 = ValueNoise3D(x0, y1, z0, seed);
n1 = ValueNoise3D(x1, y1, z0, seed);
ix1 = NoiseMath.Linear(n0, n1, xs);
iy0 = NoiseMath.Linear(ix0, ix1, ys);
n0 = ValueNoise3D(x0, y0, z1, seed);
n1 = ValueNoise3D(x1, y0, z1, seed);
ix0 = NoiseMath.Linear(n0, n1, xs);
n0 = ValueNoise3D(x0, y1, z1, seed);
n1 = ValueNoise3D(x1, y1, z1, seed);
ix1 = NoiseMath.Linear(n0, n1, xs);
iy1 = NoiseMath.Linear(ix0, ix1, ys);
return(NoiseMath.Linear(iy0, iy1, zs));
}
/// <summary>
/// Create a new NoiseCube from the given source NoiseCube using trilinear filtering.
///
/// When the sample is outside the source BorderValue is used by default. If <see cref="clamp"/>/>
/// is set clamping is used instead.
/// </summary>
/// <param name="src">The source NoiseCube</param>
/// <param name="width">Width of the new NoiseCube</param>
/// <param name="height">Height of the new NoiseCube</param>
/// <param name="depth">Depth of the new NoiseCube</param>
/// <param name="clamp">Use clamping when the sample is outside the source NoiseCube</param>
/// <returns>The new NoiseCube</returns>
public static NoiseCube TrilinearFilter(NoiseCube src, int width, int height, int depth, bool clamp = false)
{
var dest = new NoiseCube(width, height, depth);
float xratio = (float)src.Width / dest.Width;
float yratio = (float)src.Height / dest.Height;
float zratio = (float)src.Depth / dest.Depth;
Parallel.For(0, dest.Depth, z =>
{
for (int y = 0; y < dest.Height; ++y)
{
for (int x = 0; x < dest.Width; ++x)
{
float u = (x + 0.5f) * xratio - 0.5f;
float v = (y + 0.5f) * yratio - 0.5f;
float w = (z + 0.5f) * zratio - 0.5f;
int x0 = NoiseMath.FastFloor(u);
int y0 = NoiseMath.FastFloor(v);
int z0 = NoiseMath.FastFloor(w);
int x1 = x0 + 1;
int y1 = y0 + 1;
int z1 = z0 + 1;
float xf = u - x0;
float yf = v - y0;
float zf = w - z0;
if (clamp)
{
x0 = NoiseMath.Clamp(x0, 0, src.Width - 1);
x1 = NoiseMath.Clamp(x1, 0, src.Width - 1);
y0 = NoiseMath.Clamp(y0, 0, src.Height - 1);
y1 = NoiseMath.Clamp(y1, 0, src.Height - 1);
z0 = NoiseMath.Clamp(z0, 0, src.Depth - 1);
z1 = NoiseMath.Clamp(z1, 0, src.Depth - 1);
}
float c000 = src.GetValue(x0, y0, z0);
float c001 = src.GetValue(x0, y0, z1);
float c010 = src.GetValue(x0, y1, z0);
float c011 = src.GetValue(x0, y1, z1);
float c100 = src.GetValue(x1, y0, z0);
float c101 = src.GetValue(x1, y0, z1);
float c110 = src.GetValue(x1, y1, z0);
float c111 = src.GetValue(x1, y1, z1);
float val = NoiseMath.Trilinear(xf, yf, zf,
c000, c001, c010, c011, c100, c101, c110, c111);
dest.SetValue(x, y, z, val);
}
}
});
return(dest);
}
/// <summary>
/// Create a new NoiseMap from the given source NoiseMap using bilinear filtering.
///
/// When the sample is outside the source BorderValue is used by default. If <see cref="clamp"/>/>
/// is set clamping is used instead.
/// </summary>
/// <param name="src">The source NoiseMap</param>
/// <param name="width">Width of the new NoiseMap</param>
/// <param name="height">Height of the new NoiseMap</param>
/// <param name="clamp">Use clamping when the sample is outside the source NoiseMap</param>
/// <returns>The new NoiseMap</returns>
public static NoiseMap BilinearFilter(NoiseMap src, int width, int height, bool clamp = false)
{
var dest = new NoiseMap(width, height);
var xratio = (float)src.Width / dest.Width;
var yratio = (float)src.Height / dest.Height;
Parallel.For(0, dest.Height, y =>
{
for (var x = 0; x < dest.Width; ++x)
{
var u = (x + 0.5f) * xratio - 0.5f;
var v = (y + 0.5f) * yratio - 0.5f;
var x0 = NoiseMath.FastFloor(u);
var y0 = NoiseMath.FastFloor(v);
var x1 = x0 + 1;
var y1 = y0 + 1;
var xf = u - x0;
var yf = v - y0;
if (clamp)
{
x0 = NoiseMath.Clamp(x0, 0, src.Width - 1);
x1 = NoiseMath.Clamp(x1, 0, src.Width - 1);
y0 = NoiseMath.Clamp(y0, 0, src.Height - 1);
y1 = NoiseMath.Clamp(y1, 0, src.Height - 1);
}
var c00 = src.GetValue(x0, y0);
var c01 = src.GetValue(x0, y1);
var c10 = src.GetValue(x1, y0);
var c11 = src.GetValue(x1, y1);
var val = NoiseMath.Bilinear(xf, yf, c00, c01, c10, c11);
dest.SetValue(x, y, val);
}
});
return(dest);
}
