   <b>SPHERE_T3</b> is a sphere, tiled with an 8 by 8 array of
      logically triangular patches.
      <ul>
        <li>
          <a href = "../../data/polygonal_surface/sphere_t3_nodes.txt">
          sphere_t3_nodes.txt</a>, the node file;
        </li>
        <li>
          <a href = "../../data/polygonal_surface/sphere_t3_faces.txt">
          sphere_t3_faces.txt</a>, the face file;
        </li>
        <li>
          <a href = "../../data/polygonal_surface/sphere_t3.png">
          sphere_t3.png</