title: Vertically fill 3d matplotlib plot
body: <p>I have a 3d plot made using matplotlib. I now want to fill the vertical space between the drawn line and the x,y axis to highlight the height of the line on the z axis. On a 2d plot this would be done with <code>fill_between</code> but there does not seem to be anything similar for a 3d plot. Can anyone help?</p>
  
  <p>here is my current code</p>
  
  <pre><code>from stravalib import Client
  import matplotlib as mpl
  import numpy as np
  import matplotlib.pyplot as plt
  
  ... code to get the data ....
  
  mpl.rcParams['legend.fontsize'] = 10
  
  fig = plt.figure()
  ax = fig.gca(projection='3d')
  zi = alt
  x = df['x'].tolist()
  y = df['y'].tolist()
  ax.plot(x, y, zi, label='line')
  ax.legend()
  plt.show()     
  </code></pre>
  
  <p>and the current plot </p>
  
  <p><a href="https://i.stack.imgur.com/aS71M.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/aS71M.png" alt="enter image description here"></a></p>
  
  <p>just to be clear I want a vertical fill to the x,y axis intersection NOT this...</p>
  
  <p><a href="https://i.stack.imgur.com/ootDh.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/ootDh.png" alt="enter image description here"></a></p>