title: How to draw a curve in A-frame?
body: <p>I'm getting started with A-Frame and this is a very basic question. I checked a number of examples to draw a line and then a curve in A-Frame but they don't show up in the scene. I have a plane there that shows up correctly.</p>
  
  <p>I can use <code>document.querySelector('a-plane').object3D;</code> to get the plane but <code>document.querySelector('a-curve').object3D;</code> returns undefined.</p>
  
  <p>Here is a code sample:</p>
  
  <pre><code>&lt;!DOCTYPE html&gt;
  &lt;html&gt;
    &lt;head&gt;
      &lt;title&gt;A-frame room&lt;/title&gt;
      &lt;script src="https://aframe.io/releases/0.5.0/aframe.min.js"&gt;&lt;/script&gt;
    &lt;/head&gt;
    &lt;body&gt;
      &lt;a-scene&gt;
          &lt;a-plane position="0 0 -4" rotation="-90 0 0" width="4" height="4" color="#7BC8A4"&gt;   &lt;/a-plane&gt;
          &lt;a-sky color="#ffffff"&gt;&lt;/a-sky&gt;
          &lt;a-curve type="CatmullRom" curve="closed:true" visible="true"&gt;
              &lt;a-curve-point id="checkpoint1" position="0 0 -4" visible="true"&gt;&lt;/a-curve-point&gt;
              &lt;a-curve-point id="checkpoint2" position="0 10 -4" visible="true"&gt;&lt;/a-curve-point&gt;
              &lt;a-curve-point id="checkpoint3" position="0 10 -8" visible="true"&gt;&lt;/a-curve-point&gt;
              &lt;a-curve-point id="checkpoint4" position="0 0 -8" visible="true"&gt;&lt;/a-curve-point&gt;
          &lt;/a-curve&gt;
      &lt;/a-scene&gt;
    &lt;/body&gt;
  &lt;/html&gt;
  </code></pre>