title: Combining multiple line geometries into a single geometry
body: <p>I am completely new to Three.js and I am try to add edges to solid models.</p>
  
  <p>The problem is if I add the edges individually the rendering becomes slow. So thinking of combining the geometries into a single so that the rendering speeds up a bit.</p>
  
  <p>I came across this : <a href="https://github.com/mrdoob/three.js/issues/1370" rel="nofollow">https://github.com/mrdoob/three.js/issues/1370</a>
  But the output is not remaining correct after using above technique.</p>
  
  <p>My code so far below:</p>
  
  <pre><code>/* Edge Data */
  var vertices = edgeData.vertices;
  var edges = edgeData.edges;
  
  // Final Geometry
  var combinedGeo = new THREE.Geometry();
  
  /* Add lines */
  for( var i=0; i&lt;edges.length; i++){
      var geom = new THREE.Geometry();
      for (var j=0; j&lt;edges[i].length; j++){
          var v1 = vertices[edges[i][j]];
          geom.vertices.push(new THREE.Vector3(v1[0], v1[1], v1[2]));
      }
  
      // var line = new THREE.Line(geom, material, THREE.LinePieces);
      THREE.GeometryUtils.merge( combinedGeo, geom);
      // scene.add(line);
  }
  var edgesGeo = new THREE.Line(combinedGeo, material, THREE.LineStrip);
  scene.add(edgesGeo);
  </code></pre>