is frame can be seen
    as an oriented disc with null translation, unit radius, and null
    rotation, encoded as the 4D vector <code/>[0;0;1;0]</code>;
    alternatively, it can be seen as an oriented ellipse with affine
    transformation $(I,0)$ encoded as a 6D
    vector <code/>[0;0;1;0;0;1]</code>. Figure generated
    by <code/>vl_demo_frame</code>.
  </span>
 </div>
</div>

<p>This figure was generated by using the <code/>vl_plotframe</code>
function:</p>

<div class="highlight"><pre><span class="n"