Updates fractal seeding to use new numpy seed generator.

gprMax/fractals.py

@@ -83,8 +83,8 @@ class FractalSurface:
                        * (surfacedims[1]) / 2])
 
         # 2D array of random numbers to be convolved with the fractal function
-        R = np.random.RandomState(self.seed)
-        A = R.randn(surfacedims[0], surfacedims[1])
+        rng = np.random.default_rng(seed=self.seed)
+        A = rng.standard_normal(size=(surfacedims[0], surfacedims[1]))
 
         # 2D FFT
         A = fftpack.fftn(A)
@@ -176,8 +176,8 @@ class FractalVolume:
                        * self.ny / 2, self.weighting[2] * self.nz / 2])
 
         # 3D array of random numbers to be convolved with the fractal function
-        R = np.random.RandomState(self.seed)
-        A = R.randn(self.nx, self.ny, self.nz)
+        rng = np.random.default_rng(seed=self.seed)
+        A = rng.standard_normal(size=(self.nx, self.ny, self.nz))
 
         # 3D FFT
         A = fftpack.fftn(A)