diff --git a/gprMax/fractals.py b/gprMax/fractals.py
index 25c2925b..cba5afa6 100644
--- a/gprMax/fractals.py
+++ b/gprMax/fractals.py
@@ -56,12 +56,8 @@ class FractalSurface(object):
         self.filldepth = 0
         self.grass = []
 
-    def generate_fractal_surface(self, G):
-        """Generate a 2D array with a fractal distribution.
-
-        Args:
-            G (class): Grid class instance - holds essential parameters describing the model.
-        """
+    def generate_fractal_surface(self):
+        """Generate a 2D array with a fractal distribution."""
 
         if self.xs == self.xf:
             surfacedims = (self.ny + 1, self.nz + 1)
@@ -134,12 +130,8 @@ class FractalVolume(object):
         self.nbins = 0
         self.fractalsurfaces = []
 
-    def generate_fractal_volume(self, G):
-        """Generate a 3D volume with a fractal distribution.
-
-        Args:
-            G (class): Grid class instance - holds essential parameters describing the model.
-        """
+    def generate_fractal_volume(self):
+        """Generate a 3D volume with a fractal distribution."""
 
         self.fractalvolume = np.zeros((self.nx + 1, self.ny + 1, self.nz + 1), dtype=complextype)
 
diff --git a/gprMax/input_cmds_geometry.py b/gprMax/input_cmds_geometry.py
index 91dc10b7..06d1f88c 100644
--- a/gprMax/input_cmds_geometry.py
+++ b/gprMax/input_cmds_geometry.py
@@ -981,7 +981,7 @@ def process_geometrycmds(geometry, G):
                         if surface.surfaceID in existingsurfaceIDs:
                             raise CmdInputError("'" + ' '.join(tmp) + "'" + ' has already been used on the {} surface'.format(surface.surfaceID))
 
-                        surface.generate_fractal_surface(G)
+                        surface.generate_fractal_surface()
                         volume.fractalsurfaces.append(surface)
 
                         if G.messages:
@@ -1191,7 +1191,7 @@ def process_geometrycmds(geometry, G):
                         # Set the fractal range to scale the fractal distribution between zero and one
                         surface.fractalrange = (0, 1)
                         surface.operatingonID = volume.ID
-                        surface.generate_fractal_surface(G)
+                        surface.generate_fractal_surface()
                         if numblades > surface.fractalsurface.shape[0] * surface.fractalsurface.shape[1]:
                             raise CmdInputError("'" + ' '.join(tmp) + "'" + ' the specified surface is not large enough for the number of grass blades/roots specified')
 
@@ -1287,7 +1287,7 @@ def process_geometrycmds(geometry, G):
                     materialnumID = next(x.numID for x in G.materials if x.ID == volume.operatingonID)
                     volume.fractalvolume *= materialnumID
                 else:
-                    volume.generate_fractal_volume(G)
+                    volume.generate_fractal_volume()
                     volume.fractalvolume += mixingmodel.startmaterialnum
 
                 volume.generate_volume_mask()
@@ -1500,7 +1500,7 @@ def process_geometrycmds(geometry, G):
                 if volume.nbins == 1:
                     raise CmdInputError("'" + ' '.join(tmp) + "'" + ' is being used with a single material and no modifications, therefore please use a #box command instead.')
                 else:
-                    volume.generate_fractal_volume(G)
+                    volume.generate_fractal_volume()
                     volume.fractalvolume += mixingmodel.startmaterialnum
 
                 data = volume.fractalvolume.astype('int16', order='C')