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<li><a class="reference internal" href="#">Filtering a PointCloud using a PassThrough filter</a></li>
<li><a class="reference internal" href="#the-code">The code</a></li>
<li><a class="reference internal" href="#the-explanation">The explanation</a></li>
<li><a class="reference internal" href="#compiling-and-running-the-program">Compiling and running the program</a></li>
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<div class="section" id="filtering-a-pointcloud-using-a-passthrough-filter">
<span id="passthrough"></span><h1>Filtering a PointCloud using a PassThrough filter</h1>
<p>In this tutorial we will learn how to perform a simple filtering along a
specified dimension that is, cut off values that are either inside or
outside a given user range.</p>
</div>
<div class="section" id="the-code">
<h1>The code</h1>
<p>First, create a file, lets say, <code class="docutils literal notranslate"><span class="pre">passthrough.cpp</span></code> in your favorite
editor, and place the following inside it:</p>
<div class="highlight-cpp notranslate"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
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44</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="cp">#include</span> <span class="cpf">&lt;iostream&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;pcl/point_types.h&gt;</span><span class="cp"></span>
<span class="cp">#include</span> <span class="cpf">&lt;pcl/filters/passthrough.h&gt;</span><span class="cp"></span>
<span class="kt">int</span>
<span class="nf">main</span> <span class="p">()</span>
<span class="p">{</span>
<span class="n">pcl</span><span class="o">::</span><span class="n">PointCloud</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;::</span><span class="n">Ptr</span> <span class="n">cloud</span> <span class="p">(</span><span class="k">new</span> <span class="n">pcl</span><span class="o">::</span><span class="n">PointCloud</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;</span><span class="p">);</span>
<span class="n">pcl</span><span class="o">::</span><span class="n">PointCloud</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;::</span><span class="n">Ptr</span> <span class="n">cloud_filtered</span> <span class="p">(</span><span class="k">new</span> <span class="n">pcl</span><span class="o">::</span><span class="n">PointCloud</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;</span><span class="p">);</span>
<span class="c1">// Fill in the cloud data</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">width</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">height</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">points</span><span class="p">.</span><span class="n">resize</span> <span class="p">(</span><span class="n">cloud</span><span class="o">-&gt;</span><span class="n">width</span> <span class="o">*</span> <span class="n">cloud</span><span class="o">-&gt;</span><span class="n">height</span><span class="p">);</span>
<span class="k">for</span> <span class="p">(</span><span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Cloud before filtering: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="k">const</span> <span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud</span><span class="p">)</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="c1">// Create the filtering object</span>
<span class="n">pcl</span><span class="o">::</span><span class="n">PassThrough</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;</span> <span class="n">pass</span><span class="p">;</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setInputCloud</span> <span class="p">(</span><span class="n">cloud</span><span class="p">);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setFilterFieldName</span> <span class="p">(</span><span class="s">&quot;z&quot;</span><span class="p">);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setFilterLimits</span> <span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">);</span>
<span class="c1">//pass.setFilterLimitsNegative (true);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">filter</span> <span class="p">(</span><span class="o">*</span><span class="n">cloud_filtered</span><span class="p">);</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Cloud after filtering: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="k">const</span> <span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud_filtered</span><span class="p">)</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">return</span> <span class="p">(</span><span class="mi">0</span><span class="p">);</span>
<span class="p">}</span>
</pre></div>
</td></tr></table></div>
</div>
<div class="section" id="the-explanation">
<h1>The explanation</h1>
<p>Now, lets break down the code piece by piece.</p>
<p>In the following lines, we define the Point Clouds structures, fill in the
input cloud, and display its content to screen.</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span> <span class="c1">// Fill in the cloud data</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">width</span> <span class="o">=</span> <span class="mi">5</span><span class="p">;</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">height</span> <span class="o">=</span> <span class="mi">1</span><span class="p">;</span>
<span class="n">cloud</span><span class="o">-&gt;</span><span class="n">points</span><span class="p">.</span><span class="n">resize</span> <span class="p">(</span><span class="n">cloud</span><span class="o">-&gt;</span><span class="n">width</span> <span class="o">*</span> <span class="n">cloud</span><span class="o">-&gt;</span><span class="n">height</span><span class="p">);</span>
<span class="k">for</span> <span class="p">(</span><span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud</span><span class="p">)</span>
<span class="p">{</span>
<span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">=</span> <span class="mi">1024</span> <span class="o">*</span> <span class="n">rand</span> <span class="p">()</span> <span class="o">/</span> <span class="p">(</span><span class="n">RAND_MAX</span> <span class="o">+</span> <span class="mf">1.0f</span><span class="p">);</span>
<span class="p">}</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Cloud before filtering: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="k">const</span> <span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud</span><span class="p">)</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
<p>Then, we create the PassThrough filter object, and set its parameters. The
filter field name is set to the z coordinate, and the accepted interval values
are set to (0.0;1.0).</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span> <span class="n">pcl</span><span class="o">::</span><span class="n">PassThrough</span><span class="o">&lt;</span><span class="n">pcl</span><span class="o">::</span><span class="n">PointXYZ</span><span class="o">&gt;</span> <span class="n">pass</span><span class="p">;</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setInputCloud</span> <span class="p">(</span><span class="n">cloud</span><span class="p">);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setFilterFieldName</span> <span class="p">(</span><span class="s">&quot;z&quot;</span><span class="p">);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">setFilterLimits</span> <span class="p">(</span><span class="mf">0.0</span><span class="p">,</span> <span class="mf">1.0</span><span class="p">);</span>
<span class="c1">//pass.setFilterLimitsNegative (true);</span>
<span class="n">pass</span><span class="p">.</span><span class="n">filter</span> <span class="p">(</span><span class="o">*</span><span class="n">cloud_filtered</span><span class="p">);</span>
</pre></div>
</div>
<p>Finally we show the content of the filtered cloud.</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span> <span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot;Cloud after filtering: &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
<span class="k">for</span> <span class="p">(</span><span class="k">const</span> <span class="k">auto</span><span class="o">&amp;</span> <span class="nl">point</span><span class="p">:</span> <span class="o">*</span><span class="n">cloud_filtered</span><span class="p">)</span>
<span class="n">std</span><span class="o">::</span><span class="n">cerr</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span> <span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">x</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">y</span> <span class="o">&lt;&lt;</span> <span class="s">&quot; &quot;</span>
<span class="o">&lt;&lt;</span> <span class="n">point</span><span class="p">.</span><span class="n">z</span> <span class="o">&lt;&lt;</span> <span class="n">std</span><span class="o">::</span><span class="n">endl</span><span class="p">;</span>
</pre></div>
</div>
</div>
<div class="section" id="compiling-and-running-the-program">
<h1>Compiling and running the program</h1>
<p>Add the following lines to your CMakeLists.txt file:</p>
<div class="highlight-cmake notranslate"><table class="highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre> 1
2
3
4
5
6
7
8
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12</pre></div></td><td class="code"><div class="highlight"><pre><span></span><span class="nb">cmake_minimum_required</span><span class="p">(</span><span class="s">VERSION</span> <span class="s">3.5</span> <span class="s">FATAL_ERROR</span><span class="p">)</span>
<span class="nb">project</span><span class="p">(</span><span class="s">passthrough</span><span class="p">)</span>
<span class="nb">find_package</span><span class="p">(</span><span class="s">PCL</span> <span class="s">1.2</span> <span class="s">REQUIRED</span><span class="p">)</span>
<span class="nb">include_directories</span><span class="p">(</span><span class="o">${</span><span class="nv">PCL_INCLUDE_DIRS</span><span class="o">}</span><span class="p">)</span>
<span class="nb">link_directories</span><span class="p">(</span><span class="o">${</span><span class="nv">PCL_LIBRARY_DIRS</span><span class="o">}</span><span class="p">)</span>
<span class="nb">add_definitions</span><span class="p">(</span><span class="o">${</span><span class="nv">PCL_DEFINITIONS</span><span class="o">}</span><span class="p">)</span>
<span class="nb">add_executable</span> <span class="p">(</span><span class="s">passthrough</span> <span class="s">passthrough.cpp</span><span class="p">)</span>
<span class="nb">target_link_libraries</span> <span class="p">(</span><span class="s">passthrough</span> <span class="o">${</span><span class="nv">PCL_LIBRARIES</span><span class="o">}</span><span class="p">)</span>
</pre></div>
</td></tr></table></div>
<p>After you have made the executable, you can run it. Simply do:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span>$ ./passthrough
</pre></div>
</div>
<p>You will see something similar to:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">Cloud</span> <span class="n">before</span> <span class="n">filtering</span><span class="p">:</span>
<span class="mf">0.352222</span> <span class="o">-</span><span class="mf">0.151883</span> <span class="o">-</span><span class="mf">0.106395</span>
<span class="o">-</span><span class="mf">0.397406</span> <span class="o">-</span><span class="mf">0.473106</span> <span class="mf">0.292602</span>
<span class="o">-</span><span class="mf">0.731898</span> <span class="mf">0.667105</span> <span class="mf">0.441304</span>
<span class="o">-</span><span class="mf">0.734766</span> <span class="mf">0.854581</span> <span class="o">-</span><span class="mf">0.0361733</span>
<span class="o">-</span><span class="mf">0.4607</span> <span class="o">-</span><span class="mf">0.277468</span> <span class="o">-</span><span class="mf">0.916762</span>
<span class="n">Cloud</span> <span class="n">after</span> <span class="n">filtering</span><span class="p">:</span>
<span class="o">-</span><span class="mf">0.397406</span> <span class="o">-</span><span class="mf">0.473106</span> <span class="mf">0.292602</span>
<span class="o">-</span><span class="mf">0.731898</span> <span class="mf">0.667105</span> <span class="mf">0.441304</span>
</pre></div>
</div>
<p>A graphical display of the filtering process is shown below.</p>
<img alt="_images/passthrough_2.png" src="_images/passthrough_2.png" />
<p>Note that the coordinate axes are represented as red (x), green (y), and blue
(z). The five points are represented with green as the points remaining after
filtering and red as the points that have been removed by the filter.</p>
<p>As an exercise, try uncommenting this line</p>
<div class="highlight-cpp notranslate"><div class="highlight"><pre><span></span> <span class="c1">//pass.setFilterLimitsNegative (true);</span>
</pre></div>
</div>
<p>and run the program again.</p>
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