public FractionalBrownianMotionFunction(INoiseProvider provider, Random rng, double scale, int octaves, double persistence = 0.5, double lacunarity = 2.0, Func<double, double> octaveModifier = null, double? xPeriod = null, double? yPeriod = null, SampleMode mode = SampleMode.Sample2D)
{
_octaveModifier = octaveModifier;
_octaves = new Tuple<double, IFunction2D>[octaves];
bool tiling = xPeriod != null || yPeriod != null;
if (tiling && xPeriod == null)
{
xPeriod = yPeriod;
}
if (tiling && yPeriod == null)
{
yPeriod = xPeriod;
}
_maxAmplitude = 0.0;
var amplitude = 1.0;
var frequency = scale;
for (var i = 0; i < octaves; i++)
{
IFunction2D noise;
switch (mode)
{
case SampleMode.Sample2D:
noise = provider.Create2D(rng, frequency);
break;
case SampleMode.Slice3D:
noise = provider.Slice3D(rng, frequency);
break;
case SampleMode.Slice4D:
noise = provider.Slice4D(rng, frequency);
break;
case SampleMode.Tileable2D:
noise = provider.Create2D(rng, frequency, xPeriod.Value, yPeriod.Value);
break;
default:
throw new InvalidOperationException();
}
_octaves[i] = Tuple.Create(amplitude, noise);
_maxAmplitude += amplitude;
amplitude *= persistence;
frequency *= lacunarity;
}
}
private IFunction2D CreateNoiseFunction(INoiseProvider provider, Random rng)
{
if (_octaves == 1 && _power == 1.0 && !_absoluteValue)
{
// Simple case that doesn't need fBm, so we can just return a basic noise function
// to remove some overhead for benchmarking.
switch (_mode)
{
case SampleMode.Sample2D:
return provider.Create2D(rng, _scale);
case SampleMode.Slice3D:
return provider.Slice3D(rng, _scale);
case SampleMode.Slice4D:
return provider.Slice4D(rng, _scale);
case SampleMode.Tileable2D:
return provider.Create2D(rng, _scale, _size, _size);
default:
throw new InvalidOperationException();
}
}
Func<double, double> modifier = null;
if (_absoluteValue)
{
if (_power == 1.0)
{
modifier = input => (1.0 - Math.Abs(input)) * 2.0 - 1.0;
}
else
{
modifier = input => Math.Pow(1.0 - Math.Abs(input), _power) * 2.0 - 1.0;
}
}
else if (_power != 1.0)
{
modifier = input => input < 0 ? -Math.Pow(-input, _power) : Math.Pow(input, _power);
}
return provider.FractionalBrownianMotion(rng, _scale, _octaves, _persistence, _lacunarity, modifier, _size, _size, _mode);
}