title: python matplotlib invisible point
body: <p>I am learning matplolib. I try do display specific point on a surface and I get the following result :</p>
  
  <p><img src="https://i.stack.imgur.com/MyWwY.png" alt="We can hardly see the point here">
  <img src="https://i.stack.imgur.com/Lngc1.png" alt="Here we can&#39;t"></p>
  
  <p>Both screenshot comes from the same figure. On the first one, we can hardly see the point I want to display, not on the second. I would like to make it appears on each. Here is my code :</p>
  
  <pre><code>import numpy as np
  from matplotlib import cm
  from mpl_toolkits.mplot3d import Axes3D
  import matplotlib.pyplot as plt
  
  hours, pauses, results = [], [], []
  
  with open('./data.txt', 'r') as f:
      for line in f:
          value = line.split()
          for i, l in enumerate([hours, pauses, results]):
              l.append(int(value[i]))
  
  for l in [hours, pauses, results]:
      l = np.asarray(l, dtype=float)
  
  fig = plt.figure()
  ax = fig.add_subplot(111, projection='3d')
  
  m = len(hours)
  
  WP_init = 5 * np.random.rand()
  WH_init = 5 * np.random.rand()
  Z_init = 0
  for i in range(m):
      Z_init += 1. / (2 * m) * (WH_init * hours[i] + WP_init * pauses[i] - results[i])**2
  ax.scatter(WH_init, WP_init, Z_init, s=40, c='r', marker='o')
  
  
  WH = np.arange(-5, 5, 0.25)
  WP = np.arange(-5, 5, 0.25)
  WH, WP = np.meshgrid(WH, WP)
  Z = np.zeros(np.shape(WP))
  for i in range(m):
      Z += 1. / (2 * m) * (WH * hours[i] + WP * pauses[i] - results[i])**2
  
  ax.plot_surface(WH, WP, Z, rstride=4, cstride=4, cmap=cm.coolwarm)
  
  plt.show()
  </code></pre>
  
  <p>Do you know how I could fix these ?</p>
  
  <p>Thanks</p>
  
  <p>edit : here is the content of data.txt :<br>
  12 0 13<br>
  12 8 18<br>
  10 0 14<br>
  10 4 16<br>
  8 0 14<br>
  8 2 15<br>
  8 8 8<br>
  6 0 13<br>
  6 3 11<br>
  4 0 8<br>
  4 4 4<br>
  2 2 2<br>
  0 0 0</p>