<h3 dir="auto">Bug report</h3>
<p dir="auto"><strong>Bug summary</strong></p>
<p dir="auto">Artifacts appear when plotting periodic data with discontinuities, i.e. something like x mod 1.0<br>
The bug appears at when render resolution is relatively small comparing to the real resolution of the data (downsampling problem?).</p>
<p dir="auto"><strong>Code for reproduction</strong></p>

<div class="highlight highlight-source-python notranslate position-relative overflow-auto" dir="auto" data-snippet-clipboard-copy-content="import numpy as np
import matplotlib.pyplot as plt

xx, yy = np.meshgrid(np.linspace(-5, 5, 201), np.linspace(-5, 5, 201))
psi = xx % 1.0

plt.figure()
plt.imshow(psi, cmap=&quot;twilight&quot;)
plt.savefig(&quot;small.png&quot;, dpi=100)
plt.savefig(&quot;large.png&quot;, dpi=200)"><pre class="notranslate"><span class="pl-k">import</span> <span class="pl-s1">numpy</span> <span class="pl-k">as</span> <span class="pl-s1">np</span>
<span class="pl-k">import</span> <span class="pl-s1">matplotlib</span>.<span class="pl-s1">pyplot</span> <span class="pl-k">as</span> <span class="pl-s1">plt</span>

<span class="pl-s1">xx</span>, <span class="pl-s1">yy</span> <span class="pl-c1">=</span> <span class="pl-s1">np</span>.<span class="pl-en">meshgrid</span>(<span class="pl-s1">np</span>.<span class="pl-en">linspace</span>(<span class="pl-c1">-</span><span class="pl-c1">5</span>, <span class="pl-c1">5</span>, <span class="pl-c1">201</span>), <span class="pl-s1">np</span>.<span class="pl-en">linspace</span>(<span class="pl-c1">-</span><span class="pl-c1">5</span>, <span class="pl-c1">5</span>, <span class="pl-c1">201</span>))
<span class="pl-s1">psi</span> <span class="pl-c1">=</span> <span class="pl-s1">xx</span> <span class="pl-c1">%</span> <span class="pl-c1">1.0</span>

<span class="pl-s1">plt</span>.<span class="pl-en">figure</span>()
<span class="pl-s1">plt</span>.<span class="pl-en">imshow</span>(<span class="pl-s1">psi</span>, <span class="pl-s1">cmap</span><span class="pl-c1">=</span><span class="pl-s">"twilight"</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">savefig</span>(<span class="pl-s">"small.png"</span>, <span class="pl-s1">dpi</span><span class="pl-c1">=</span><span class="pl-c1">100</span>)
<span class="pl-s1">plt</span>.<span class="pl-en">savefig</span>(<span class="pl-s">"large.png"</span>, <span class="pl-s1">dpi</span><span class="pl-c1">=</span><span class="pl-c1">200</span>)</pre></div>
<p dir="auto"><strong>Outcome</strong></p>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/11896426/113173843-173c6000-924a-11eb-907f-3bb546a0941b.png"><img src="https://user-images.githubusercontent.com/11896426/113173843-173c6000-924a-11eb-907f-3bb546a0941b.png" alt="alt text" width="40%" style="max-width: 100%;"></a> <a target="_blank" rel="noopener noreferrer nofollow" href="https://user-images.githubusercontent.com/11896426/113173851-199eba00-924a-11eb-95b4-97b2b6262ed7.png"><img src="https://user-images.githubusercontent.com/11896426/113173851-199eba00-924a-11eb-95b4-97b2b6262ed7.png" alt="alt text" width="40%" style="max-width: 100%;"></a></p>
<p dir="auto">(large.png, small.png)</p>
<p dir="auto"><strong>Matplotlib version</strong></p>
<p dir="auto">The issue is repeatable locally and in CoLab:</p>

<ul dir="auto">
<li>Operating system: Linux</li>
<li>Matplotlib version: 3.3.3, 3.2.2</li>
<li>Matplotlib backend (): TkAgg, ipykernel.pylab.backend_inline</li>
<li>Python version: 3.8.5, 3.7</li>
</ul>
<p dir="auto">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 result.<br>
I just want to know the difference of plot_trisurf between matplotlib 2.0.2 and matplotlib 1.3.1. And how i can get the similar result?<br>
the details about this issue are referred to  <a href="https://stackoverflow.com/questions/44244297/plot-trisurf-of-matplotlib-2-0-2" rel="nofollow">https://stackoverflow.com/questions/44244297/plot-trisurf-of-matplotlib-2-0-2</a></p>