How to use the discretize.TreeMesh function in discretize

dz = 5    # minimum cell width (base mesh cell width) in z

x_length = 240.     # domain width in x
y_length = 240.     # domain width in y
z_length = 120.     # domain width in y

# Compute number of base mesh cells required in x and y
nbcx = 2**int(np.round(np.log(x_length/dx)/np.log(2.)))
nbcy = 2**int(np.round(np.log(y_length/dy)/np.log(2.)))
nbcz = 2**int(np.round(np.log(z_length/dz)/np.log(2.)))

# Define the base mesh
hx = [(dx, nbcx)]
hy = [(dy, nbcy)]
hz = [(dz, nbcz)]
mesh = TreeMesh([hx, hy, hz], x0='CCN')

# Refine based on surface topography
mesh = refine_tree_xyz(
    mesh, xyz_topo, octree_levels=[2, 2], method='surface', finalize=False
)

# Refine box based on region of interest
xp, yp, zp = np.meshgrid([-100., 100.], [-100., 100.], [-80., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]

mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[2, 2], method='box', finalize=False
)

mesh.finalize()

def make_example_mesh():

    # Base mesh parameters
    dh = 5.   # base cell size
    nbc = 32  # total width of mesh in terms of number of base mesh cells
    h = dh*np.ones(nbc)

    mesh = TreeMesh([h, h, h], x0='CCC')

    # Refine to largest possible cell size
    mesh.refine(3, finalize=False)

    return mesh

# ------------------
#
# Here, we create the OcTree mesh that will be used to predict both DC
# resistivity and IP data.
#

dh = 10.                                                    # base cell width
dom_width_x = 2400.                                         # domain width x                                        # domain width y
dom_width_z = 1200.                                         # domain width z
nbcx = 2**int(np.round(np.log(dom_width_x/dh)/np.log(2.)))  # num. base cells x
nbcz = 2**int(np.round(np.log(dom_width_z/dh)/np.log(2.)))  # num. base cells z

# Define the base mesh
hx = [(dh, nbcx)]
hz = [(dh, nbcz)]
mesh = TreeMesh([hx, hz], x0='CN')

# Mesh refinement based on topography
mesh = refine_tree_xyz(
    mesh, topo_xyz[:, [0, 2]], octree_levels=[1], method='surface', finalize=False
)

# Mesh refinement near transmitters and receivers
dc_survey.getABMN_locations()
electrode_locations = np.r_[
    dc_survey.a_locations, dc_survey.b_locations,
    dc_survey.m_locations, dc_survey.n_locations
    ]

unique_locations = np.unique(electrode_locations, axis=0)

mesh = refine_tree_xyz(

dz = 5    # minimum cell width (base mesh cell width) in z

x_length = 240.     # domain width in x
y_length = 240.     # domain width in y
z_length = 120.     # domain width in y

# Compute number of base mesh cells required in x and y
nbcx = 2**int(np.round(np.log(x_length/dx)/np.log(2.)))
nbcy = 2**int(np.round(np.log(y_length/dy)/np.log(2.)))
nbcz = 2**int(np.round(np.log(z_length/dz)/np.log(2.)))

# Define the base mesh
hx = [(dx, nbcx)]
hy = [(dy, nbcy)]
hz = [(dz, nbcz)]
mesh = TreeMesh([hx, hy, hz], x0='CCN')

# Refine based on surface topography
mesh = refine_tree_xyz(
    mesh, xyz_topo, octree_levels=[2, 2], method='surface', finalize=False
)

# Refine box base on region of interest
xp, yp, zp = np.meshgrid([-100., 100.], [-100., 100.], [-80., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]

mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[2, 2], method='box', finalize=False
)

mesh.finalize()

# ------------------
#
# Here, we create the OcTree mesh that will be used to predict both DC
# resistivity and IP data.
#

dh = 10.                                                    # base cell width
dom_width_x = 2400.                                         # domain width x
dom_width_z = 1200.                                         # domain width z
nbcx = 2**int(np.round(np.log(dom_width_x/dh)/np.log(2.)))  # num. base cells x
nbcz = 2**int(np.round(np.log(dom_width_z/dh)/np.log(2.)))  # num. base cells z

# Define the base mesh
hx = [(dh, nbcx)]
hz = [(dh, nbcz)]
mesh = TreeMesh([hx, hz], x0='CN')

# Mesh refinement based on topography
mesh = refine_tree_xyz(
    mesh, xyz_topo[:,[0, 2]], octree_levels=[1], method='surface', finalize=False
)

# Mesh refinement near transmitters and receivers. First we need to obtain the
# set of unique electrode locations.
dc_survey.getABMN_locations()
electrode_locations = np.c_[
    dc_survey.a_locations, dc_survey.b_locations,
    dc_survey.m_locations, dc_survey.n_locations
    ]

unique_locations = np.unique(
    np.reshape(electrode_locations, (4*dc_survey.nD, 2)), axis=0

# resistivity and IP data.
#

dh = 20.                                                    # base cell width
dom_width_x = 3000.                                         # domain width x
dom_width_y = 3000.                                         # domain width y
dom_width_z = 1500.                                         # domain width z
nbcx = 2**int(np.round(np.log(dom_width_x/dh)/np.log(2.)))  # num. base cells x
nbcy = 2**int(np.round(np.log(dom_width_y/dh)/np.log(2.)))  # num. base cells y
nbcz = 2**int(np.round(np.log(dom_width_z/dh)/np.log(2.)))  # num. base cells z

# Define the base mesh
hx = [(dh, nbcx)]
hy = [(dh, nbcy)]
hz = [(dh, nbcz)]
mesh = TreeMesh([hx, hy, hz], x0='CCN')

# Mesh refinement based on topography
mesh = refine_tree_xyz(
    mesh, topo_xyz, octree_levels=[0, 0, 0, 0, 1], method='surface', finalize=False
)

# Mesh refinement near transmitters and receivers
mesh = refine_tree_xyz(
    mesh, electrode_locs, octree_levels=[2, 4], method='radial', finalize=False
)

# Refine core mesh region
xp, yp, zp = np.meshgrid([-600., 600.], [-300., 300.], [-500., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]
mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[0, 2, 2], method='box', finalize=False

)

###############################################################
# Create OcTree Mesh
# ------------------
#
# Here we define the OcTree mesh that is used for this example.
#

dh = 25.                                                     # base cell width
dom_width = 1600.                                            # domain width
nbc = 2**int(np.round(np.log(dom_width/dh)/np.log(2.)))      # num. base cells

# Define the base mesh
h = [(dh, nbc)]
mesh = TreeMesh([h, h, h], x0='CCC')

# Mesh refinement based on topography
mesh = refine_tree_xyz(
    mesh, topo_xyz, octree_levels=[0, 0, 0, 1], method='surface', finalize=False
)

# Mesh refinement near transmitters and receivers
mesh = refine_tree_xyz(
    mesh, rx_locs, octree_levels=[2, 4], method='radial', finalize=False
)

# Refine core mesh region
xp, yp, zp = np.meshgrid([-300., 300.], [-300., 300.], [-300., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]
mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[0, 2, 4], method='box', finalize=False

)

###############################################################
# Create OcTree Mesh
# ------------------
#
# Here we define the OcTree mesh that is used for this example.
#

dh = 20.                                                     # base cell width
dom_width = 3000.                                            # domain width
nbc = 2**int(np.round(np.log(dom_width/dh)/np.log(2.)))      # num. base cells

# Define the base mesh
h = [(dh, nbc)]
mesh = TreeMesh([h, h, h], x0='CCC')

# Mesh refinement based on topography
mesh = refine_tree_xyz(
    mesh, topo_xyz, octree_levels=[0, 0, 0, 1], method='surface', finalize=False
)

# Mesh refinement near transmitters and receivers
mesh = refine_tree_xyz(
    mesh, rx_locs, octree_levels=[2, 4], method='radial', finalize=False
)

# Refine core mesh region
xp, yp, zp = np.meshgrid([-300., 300.], [-300., 300.], [-400., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]
mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[0, 2, 4], method='box', finalize=False

dz = 5    # minimum cell width (base mesh cell width) in z

x_length = 240.     # domain width in x
y_length = 240.     # domain width in y
z_length = 120.     # domain width in y

# Compute number of base mesh cells required in x and y
nbcx = 2**int(np.round(np.log(x_length/dx)/np.log(2.)))
nbcy = 2**int(np.round(np.log(y_length/dy)/np.log(2.)))
nbcz = 2**int(np.round(np.log(z_length/dz)/np.log(2.)))

# Define the base mesh
hx = [(dx, nbcx)]
hy = [(dy, nbcy)]
hz = [(dz, nbcz)]
mesh = TreeMesh([hx, hy, hz], x0='CCN')

# Refine based on surface topography
mesh = refine_tree_xyz(
    mesh, topo, octree_levels=[2, 2], method='surface', finalize=False
)

# Refine box base on region of interest
xp, yp, zp = np.meshgrid([-100., 100.], [-100., 100.], [-80., 0.])
xyz = np.c_[mkvc(xp), mkvc(yp), mkvc(zp)]

mesh = refine_tree_xyz(
    mesh, xyz, octree_levels=[2, 2], method='box', finalize=False
)

mesh.finalize()