import matplotlib.pyplot as plt

import numpy as np

# prepare some coordinates

x, y, z = np.indices((8, 8, 8))

# draw cuboids in the top left and bottom right corners, and a link between them

cube1 = (x < 3) & (y < 3) & (z < 3)

cube2 = (x >= 5) & (y >= 5) & (z >= 5)

link = abs(x - y) + abs(y - z) + abs(z - x) <= 2

# combine the objects into a single boolean array

voxels = cube1 | cube2 | link

# set the colors of each object

colors = np.empty(voxels.shape, dtype=object)

colors[link] = 'red'

colors[cube1] = 'blue'

colors[cube2] = 'green'

# and plot everything

fig = plt.figure(figsize=plt.figaspect(0.5))

ax, ax_shaded = fig.subplots(1, 2, subplot_kw=dict(projection='3d'))

ax.voxels(voxels, facecolors=colors, edgecolor='k', shade=False)

ax.set_title("Unshaded")

ax_shaded.voxels(voxels, facecolors=colors, edgecolor='k', shade=True)

ax_shaded.set_title("Shaded (default)")

plt.show()