import numpy as np
import matplotlib.pyplot as plt
from mpl_toolkits.mplot3d import Axes3D


# calc
L, M = np.meshgrid(np.linspace(0, 1, 1000), np.linspace(0, 1, 1000))
L = 4 * L + 4
area_top = L * (L - 4)
area_left = L * M * 4
area_right = L * L * (1 - M)
depth = (area_top - area_left) ** 2 \
      + (area_top - area_right) ** 2 \
      + (area_left - area_right) ** 2

# plot
fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')
ax.invert_yaxis()
ax.plot_wireframe(L, M * L, np.log(depth))
plt.show()