Question

I have written a 2D Perlin noise implementation based on information from here, here, here, and here. However, the output looks like this.

public static double Perlin(double X, double XScale, double Y, double YScale, double Persistance, double Octaves) {
    double total=0.0;
    for(int i=0;i<Octaves;i++){
        int frq = (int) Math.Pow(2,i);
        int amp = (int) Math.Pow(Persistance,i);
        total += InterpolatedSmoothNoise((X / XScale) * frq, (Y / YScale) * frq) * amp;
    }
return total;
}

private static double InterpolatedSmoothNoise (double X, double Y) {
int ix = (int) Math.Floor(X);
double fx = X-ix;
int iy = (int) Math.Floor(Y);
double fy = Y-iy;

double v1 = SmoothPerlin(ix,iy); //          --
double v2 = SmoothPerlin(ix+1,iy); //        +-
double v3 = SmoothPerlin(ix,iy+1);//         -+
double v4 = SmoothPerlin(ix+1,iy+1);//       ++

double i1 = Interpolate(v1,v2,fx);
double i2 = Interpolate(v3,v4,fx);

    return Interpolate(i1,i2,fy);
}

private static double SmoothPerlin (int X, int Y) {
    double sides=(Noise(X-1,Y,Z)+Noise(X+1,Y,Z)+Noise(X,Y-1,Z)+Noise(X,Y+1,Z)+Noise(X,Y,Z-1)+Noise(X,Y,Z+1))/12.0;
    double center=Noise(X,Y,Z)/2.0;
    return sides + center;
}

private static double Noise (int X, int Y) {
uint m_z = (uint) (36969 * (X & 65535) + (X >> 16));
uint m_w = (uint) (18000 * (Y & 65535) + (Y >> 16));
uint ou = (m_z << 16) + m_w;
return ((ou + 1.0) * 2.328306435454494e-10);
}

Any input on what is wrong is appreciated.

EDIT: I found a way to solve this: I used an array of doubles generated at load to fix this. Any way to implement a good random number generator is appreciated though.

Answer 1

I suppose this effect is due to your noise function (all other code looks ok).

The function

private static double Noise (int X, int Y) {
    uint m_z = (uint) (36969 * (X & 65535) + (X >> 16));
    uint m_w = (uint) (18000 * (Y & 65535) + (Y >> 16));
    uint ou = (m_z << 16) + m_w;
    return ((ou + 1.0) * 2.328306435454494e-10);
}

isn’t very noisy but strongly correlated with your input X and Y variables. Try using any other pseudo-random function which you seed with you input.