//-----------------------------------------------------------------------------

// "iqTurbulence" function by Inigo Quilez
// http://www.iquilezles.org , http://www.decarpentier.nl/scape-procedural-basics

//float iqTurbulence(vec3 point, int octaves, float lacunarity = 2.0, float gain = 0.5)
float iqTurbulence(vec3 point, int octaves, float lacunarity, float gain)
{
    float summ = 0.5;
    float freq = 1.0, amp = 1.0;
    vec2 dsum = vec2(0.0, 0.0);
    for (int i=0; i < octaves; i++)
    {
        vec4 n = NoiseDeriv(point * freq);
        dsum += n.yz;
        summ += amp * n.x / (1 + dot(dsum, dsum));
        freq *= lacunarity;
        amp *= gain;
    }
    return summ;
}

float iqTurbulence(vec3 point, int octaves, float lacunarity, float gain)
{
    gain = 0.5;          // ????
    lacunarity = 2.0;    // ????
    float summ = 0.5;
    float freq = 1.0, amp = 1.0;
    vec2 dsum = vec2(0.0, 0.0);
    for (int i=0; i < octaves; i++)
    {
        vec4 n = NoiseDeriv(point * freq);
        dsum += n.yz;
        summ += amp * n.x / (1 + dot(dsum, dsum));
        freq *= lacunarity;
        amp *= gain;
    }
    return summ;
}