title: How to use plot_trisurf
body: <p>After updating matplotlib version from 1.3.1 to 2.0.2, when I want to use plot_trisurf to generate a TIN by 3d-points, I got an incomprehensible results. My test code is following:</p>
  
  <pre><code>import sys
  import matplotlib
  import matplotlib.pyplot as plt
  from matplotlib.ticker import MaxNLocator
  from matplotlib import cm
  from mpl_toolkits.mplot3d import Axes3D
  import numpy
  from numpy.random import randn
  from scipy import array, newaxis
  
  chunk = numpy.loadtxt('test.xyz')  #test.xyz contains 38010 points,
  DATA=numpy.array(chunk)
  Xs = DATA[:,0]
  Ys = DATA[:,1]
  Zs = DATA[:,2]
  
  fig = plt.figure()
  ax = fig.add_subplot(111, projection='3d')
  
  surf = ax.plot_trisurf(Xs, Ys, Zs, cmap=cm.jet, linewidth=0)
  fig.colorbar(surf)
  
  ax.xaxis.set_major_locator(MaxNLocator(5))
  ax.yaxis.set_major_locator(MaxNLocator(6))
  ax.zaxis.set_major_locator(MaxNLocator(5))
  
  fig.tight_layout()
  plt.show()
  </code></pre>
  
  <p>The test.xyz file contains 38010 points. Some portion of it is showing as follows, the complete file can be found <a href="https://github.com/zxgdll/problem-about-matplotlib2.0.2" rel="nofollow noreferrer">here</a>.</p>
  
  <pre><code>512743.63 5403547.33 308.68
  512743.62 5403547.33 308.70
  512743.61 5403547.33 308.72
  512743.60 5403547.34 308.68
  512743.60 5403547.33 308.73
  512741.50 5403547.36 309.05
  512741.50 5403547.36 309.07
  512741.49 5403547.46 309.09
  512741.48 5403547.46 309.07
  512741.47 5403547.46 309.10
  512741.47 5403547.45 309.13
  512741.46 5403547.37 309.04
  512739.39 5403547.51 309.10
  512739.39 5403547.48 309.34
  512739.38 5403547.60 309.25
  512739.37 5403547.71 309.15
  512739.39 5403547.49 310.65
  512739.39 5403547.48 310.70
  512739.38 5403547.49 310.69
  512739.37 5403547.48 310.72
  512739.36 5403547.39 310.64
  512739.32 5403547.41 309.20
  512737.33 5403547.26 313.14
  512737.33 5403547.37 313.09
  512737.32 5403547.38 313.03
  512737.30 5403547.37 313.12
  512737.30 5403547.26 313.14
  512735.22 5403547.41 311.72
  512735.22 5403547.43 312.29
  512735.22 5403547.49 312.59
  512735.21 5403547.51 312.48
  512735.20 5403547.60 312.53
  512735.19 5403547.61 312.48
  512735.18 5403547.72 312.40
  512735.18 5403547.71 312.49
  512735.17 5403547.71 312.51
  512735.16 5403547.70 312.58
  512735.15 5403547.61 312.52
  </code></pre>
  
  <p>after updating, the result is shown as：<img src="https://i.stack.imgur.com/tkClU.png" alt="]"></p>
  
  <p>I think it is wrong, because I provide enough points to generate a TIN, but  the result seems to use only a small part of the point. Before updating the matplotlib, I can get a result like:
   <img src="https://i.stack.imgur.com/9TKo2.png" alt="]"></p>