java - Perlin noise - What am I doing wrong? -

i started world generation , i've been looking tutorials on perlin noise everywhere sadly there not alot found on google. last days followed tutorial can't code work.

here java method.

private static double[][] createnoise(int xn, int yn, int sps) {     int m = yn * sps;     int n = xn * sps;     double[][] u = new double[yn + 1][];     double[][] v = new double[yn + 1][];      double[][] x = new double[m][];     double[][] y = new double[m][];     double[][] z = new double[m][];      (int = 0; < m; i++) {         x[i] = new double[n];         y[i] = new double[n];         z[i] = new double[n];     }     (int = 0; < yn + 1; i++) {         u[i] = new double[xn + 1];         v[i] = new double[xn + 1];     }      (int = 0; < xn + 1; i++) {         (int j = 0; j < yn + 1; j++) {             u[i][j] = nextrandom();             v[i][j] = nextrandom();         }     }     double hx = xn / (n - 1);     double hy = yn / (m - 1);     (int = 0; < m; i++) {         (int j = 0; j < n; j++) {             x[i][j] = hx * j;             y[i][j] = hy * i;         }     }      (int = 0; < m; i++) {         (int j = 0; j < n; j++) {             int xc = (int)x[i][j];             int yc = (int)y[i][j];              if (x[i][j] % 1 == 0 && x[i][j] != 0 ) xc = xc - 1;             if (y[i][j] % 1 == 0 && y[i][j] != 0 ) yc = yc - 1;              double xr = x[i][j] - xc;             double yr = y[i][j] - yc;             double s11[] = {-xr, -yr};             double s21[] = {-xr, 1 - yr};             double s22[] = {1 - xr, 1 - yr};             double s12[] = {1 - xr, -yr};              double q11 = s11[0] * u[yc][xc] + s11[1] * v[yc][xc];             double q21 = s21[0] * u[yc + 1][xc] + s21[1] * v[yc + 1][xc];             double q22 = s22[0] * u[yc + 1][xc + 1] + s22[1] * v[yc + 1][xc + 1];             double q12 = s12[0] * u[yc][xc + 1] + s12[1] * v[yc][xc + 1];              z[i][j] = lerp(x[i][j], y[i][j], xc, xc + 1, yc, yc + 1, q11, q12, q21, q22);         }     }      return z; } 

the heightmap method returns sadly enough looks this

as can see, first row/column working, after algorithm seems fail. made sure method

nextrandom(); 

returns float value between -1 & 1.

thanks alot!

thanks user @gawi pointing out.

hx = xn / (n - 1); 

will divide 2 integers, , return 0. can fix casting double it:

double hx = (double)xn / (n - 1); 

then map works!