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<!DOCTYPE html>
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<title>group — VPython 3.2 documentation</title>
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<section id="group">
<h1>group<a class="headerlink" href="#group" title="Permalink to this heading">¶</a></h1>
<p>A <em>group</em> is a collection of objects that can be manipulated together. Unlike a <a class="reference internal" href="compound.html"><span class="doc">compound</span></a>, the constituent objects of a group retain their individual identities and can be moved, rotated, or otherwise altered individually. Group is more expensive computationally than compound.</p>
<p>Objects are added to a group by specifying <code class="docutils literal notranslate"><span class="pre">group=mygroup</span></code> when the object is created.</p>
<dl class="py function">
<dt class="sig sig-object py" id="id0">
<span class="sig-name descname"><span class="pre">mygroup</span></span><span class="sig-paren"> = </span><span class="sig-name descname"><span class="pre">group</span></span><span class="sig-paren">()</span><a class="headerlink" href="#id0" title="Permalink to this definition">¶</a></dt>
<dd><dl class="field-list simple">
<dt class="field-odd">Parameters<span class="colon">:</span></dt>
<dd class="field-odd"><ul class="simple">
<li><p><strong>pos</strong> (<em>vector</em>) – Position of the group. Default <code class="docutils literal notranslate"><span class="pre">vec(0,0,0)</span></code>. Moving <em>pos</em> moves all objects in the group.</p></li>
<li><p><strong>axis</strong> (<em>vector</em>) – Orientation of the group. Default <code class="docutils literal notranslate"><span class="pre">vec(1,0,0)</span></code>. Changing <em>axis</em> rotates all objects in the group.</p></li>
<li><p><strong>up</strong> (<em>vector</em>) – A vector perpendicular to the axis. Setting <em>up</em> sets <em>up</em> for all objects in the group.</p></li>
<li><p><strong>color</strong> (<em>vector</em>) – Setting <em>color</em> sets the color of all objects in the group.</p></li>
<li><p><strong>visible</strong> (<em>boolean</em>) – If False, all objects in the group are hidden. Default True.</p></li>
</ul>
</dd>
</dl>
</dd></dl>
<p>Example: create a group and add objects to it:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">mygroup</span> <span class="o">=</span> <span class="n">group</span><span class="p">()</span>
<span class="n">b</span> <span class="o">=</span> <span class="n">box</span><span class="p">(</span> <span class="n">group</span><span class="o">=</span><span class="n">mygroup</span> <span class="p">)</span>
<span class="n">s</span> <span class="o">=</span> <span class="n">sphere</span><span class="p">(</span> <span class="n">pos</span><span class="o">=</span><span class="n">vec</span><span class="p">(</span><span class="mi">2</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">),</span> <span class="n">group</span><span class="o">=</span><span class="n">mygroup</span> <span class="p">)</span>
<span class="n">mygroup</span><span class="o">.</span><span class="n">pos</span> <span class="o">=</span> <span class="n">vec</span><span class="p">(</span><span class="mi">1</span><span class="p">,</span><span class="mi">0</span><span class="p">,</span><span class="mi">0</span><span class="p">)</span> <span class="c1"># moves both objects</span>
</pre></div>
</div>
<section id="group-and-world-coordinates">
<h2>Group and world coordinates<a class="headerlink" href="#group-and-world-coordinates" title="Permalink to this heading">¶</a></h2>
<p>The <em>pos</em> of each object in a group is stored relative to the group’s <em>pos</em> (group coordinates). The group provides two conversion functions:</p>
<p><code class="docutils literal notranslate"><span class="pre">world_pos = mygroup.group_to_world( v )</span></code> converts a position in group coordinates to world coordinates.</p>
<p><code class="docutils literal notranslate"><span class="pre">group_pos = mygroup.world_to_group( v )</span></code> converts a position in world coordinates to group coordinates.</p>
</section>
<section id="rotating-a-group">
<h2>Rotating a group<a class="headerlink" href="#rotating-a-group" title="Permalink to this heading">¶</a></h2>
<p>All objects in a group can be rotated together:</p>
<p><code class="docutils literal notranslate"><span class="pre">mygroup.rotate( angle=a, axis=vec(0,1,0) )</span></code></p>
<p>The optional <code class="docutils literal notranslate"><span class="pre">origin</span></code> parameter specifies the center of rotation. Default is <code class="docutils literal notranslate"><span class="pre">mygroup.pos</span></code>.</p>
<p>Changing <code class="docutils literal notranslate"><span class="pre">mygroup.axis</span></code> also rotates all member objects.</p>
</section>
<section id="restrictions-on-groups">
<h2>Restrictions on groups<a class="headerlink" href="#restrictions-on-groups" title="Permalink to this heading">¶</a></h2>
<p>Labels cannot be members of a group. Objects must be assigned to a group at creation time using the <code class="docutils literal notranslate"><span class="pre">group=</span></code> parameter; objects cannot be added to or removed from a group after creation.</p>
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