libnoise code for terrain generation

double gnoise(double x, double z)
{
    Billow modBillow;
    ScaleBias modScale;
    RidgedMulti modRidged;
    Perlin modNoise;
    ScaleBias modNoiseScale;
    Select modSelect;

    modBillow.SetNoiseQuality(NoiseQuality::QUALITY_FAST);
    modBillow.SetOctaveCount(8);
    modBillow.SetFrequency(0.15);

    modScale.SetSourceModule(0, modBillow);
    modScale.SetScale(0.125);
    modScale.SetBias(1.0);

    modNoise.SetNoiseQuality(NoiseQuality::QUALITY_FAST);
    modNoise.SetOctaveCount(8);
    modNoise.SetFrequency(0.10);
    modNoise.SetPersistence(0.25);

    modNoiseScale.SetSourceModule(0, modNoise);
    modNoiseScale.SetScale(0.45);
    modNoiseScale.SetBias(-1.0);

    modSelect.SetSourceModule(0, modScale);
    modSelect.SetSourceModule(1, modNoiseScale);
    modSelect.SetControlModule(modRidged);
    modSelect.SetBounds(-1000.0, 1000.0);
    modSelect.SetEdgeFalloff(0.125);

    double value = modSelect.GetValue(x, 0.01, z);

    return (value / 2.0) + 0.5;
}