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"""
=======================================================
3D voxel / volumetric plot with cylindrical coordinates
=======================================================
Demonstrates using the *x*, *y*, *z* parameters of `.Axes3D.voxels`.
"""
import matplotlib.pyplot as plt
import numpy as np
import matplotlib.colors
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, theta, z = np.mgrid[0:1:11j, 0:np.pi*2:25j, -0.5:0.5:11j]
x = r*np.cos(theta)
y = r*np.sin(theta)
rc, thetac, zc = midpoints(r), midpoints(theta), midpoints(z)
# define a wobbly torus about [0.7, *, 0]
sphere = (rc - 0.7)**2 + (zc + 0.2*np.cos(thetac*2))**2 < 0.2**2
# combine the color components
hsv = np.zeros(sphere.shape + (3,))
hsv[..., 0] = thetac / (np.pi*2)
hsv[..., 1] = rc
hsv[..., 2] = zc + 0.5
colors = matplotlib.colors.hsv_to_rgb(hsv)
# and plot everything
ax = plt.figure().add_subplot(projection='3d')
ax.voxels(x, y, z, sphere,
facecolors=colors,
edgecolors=np.clip(2*colors - 0.5, 0, 1), # brighter
linewidth=0.5)
plt.show()
# %%
# .. tags::
# plot-type: 3D,
# styling: color,
# level: intermediate
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