/// <summary>
/// Ridged multi-fractal
/// </summary>
/// <param name="x">Initial x coordinate</param>
/// <param name="y">Initial y coordinate</param>
/// <param name="z">Initial z coordinate</param>
/// <param name="freq">Frequency</param>
/// <param name="numOctaves">Number of octaves</param>
/// <param name="persistence">Persistence</param>
/// <param name="basis">Basis function. Generates values between 0 and 1</param>
/// <returns>Returns the generated fractal value between 0 and 1</returns>
public static float RidgedFractal( float x, float y, float z, float freq, int numOctaves, float persistence, Basis3dFunction basis )
{
float offset = 1.0f;
float signal = Math.Abs( basis( x, y, z ) );
signal = offset - signal; // invert and translate (note that "offset" should be ~= 1.0)
signal *= signal; // square the signal, to increase "sharpness" of ridges
float result = signal;
float gain = 1.8f;
float exp = 1;
float max = 1;
for ( int octave = 1; octave < numOctaves; ++octave )
{
x *= freq;
y *= freq;
z *= freq;
float weight = Utils.Clamp( signal * gain, 0, 1 );
signal = offset - Math.Abs( basis( x, y, z ) );
signal *= signal;
signal *= weight;
max += 1.0f / exp;
result += signal / exp;
exp *= freq;
}
return ( result / max );
}
/// <summary>
/// Simple fractal
/// </summary>
/// <param name="x">Initial x coordinate</param>
/// <param name="y">Initial y coordinate</param>
/// <param name="z">Initial z coordinate</param>
/// <param name="freq">Frequency</param>
/// <param name="numOctaves">Number of octaves</param>
/// <param name="persistence">Persistence</param>
/// <param name="basis">Basis function. Generates values between 0 and 1</param>
/// <returns>Returns the generated fractal value between 0 and 1</returns>
public static float SimpleFractal( float x, float y, float z, float freq, int numOctaves, float persistence, Basis3dFunction basis )
{
float amp = 1;
float total = 0;
float max = 0;
for ( int octave = 0; octave < numOctaves; ++octave )
{
total += basis( x, y, z ) * amp;
max += amp;
amp *= persistence;
x *= freq;
y *= freq;
z *= freq;
}
return ( total + max ) / ( max * 2 );
}
