Users can now toggle shading in 3D bar plots

A new ``shade`` parameter has been added the 3D

`~mpl_toolkits.mplot3d.axes3d.Axes3D.bar` plotting method. The default behavior

remains to shade the bars, but now users have the option of setting ``shade``

to ``False``.

Example

.. plot::

:include-source:

:align: center

import numpy as np

import matplotlib.pyplot as plt

from mpl_toolkits.mplot3d import Axes3D

x = np.arange(2)

y = np.arange(3)

x2d, y2d = np.meshgrid(x, y)

x, y = x2d.ravel(), y2d.ravel()

z = np.zeros_like(x)

dz = x + y

fig = plt.figure(figsize=(4, 6))

ax1 = fig.add_subplot(2, 1, 1, projection='3d')

ax1.bar3d(x, y, z, 1, 1, dz, shade=True)

ax1.set_title('Shading On')

ax2 = fig.add_subplot(2, 1, 2, projection='3d')

ax2.bar3d(x, y, z, 1, 1, dz, shade=False)

ax2.set_title('Shading Off')

plt.show()