>>> """
==========================================
3D voxel / volumetric plot with rgb colors
==========================================

Demonstrates using `.Axes3D.voxels` to visualize parts of a color space.
"""
... 
... import matplotlib.pyplot as plt
... import numpy as np
... 
... 
... def midpoints(x):
...     sl = ()
...     for i in range(x.ndim):
...         x = (x[sl + np.index_exp[:-1]] + x[sl + np.index_exp[1:]]) / 2.0
...         sl += np.index_exp[:]
...     return x
... 
... # prepare some coordinates, and attach rgb values to each
... r, g, b = np.indices((17, 17, 17)) / 16.0
... rc = midpoints(r)
... gc = midpoints(g)
... bc = midpoints(b)
... 
... # define a sphere about [0.5, 0.5, 0.5]
... sphere = (rc - 0.5)**2 + (gc - 0.5)**2 + (bc - 0.5)**2 < 0.5**2
... 
... # combine the color components
... colors = np.zeros(sphere.shape + (3,))
... colors[..., 0] = rc
... colors[..., 1] = gc
... colors[..., 2] = bc
... 
... # and plot everything
... ax = plt.figure().add_subplot(projection='3d')
... ax.voxels(r, g, b, sphere,
...           facecolors=colors,
...           edgecolors=np.clip(2*colors - 0.5, 0, 1),  # brighter
...           linewidth=0.5)
... ax.set(xlabel='r', ylabel='g', zlabel='b')
... 
... plt.show()
...