title: add image texture to line in three.js
body: <p>I want add image texture to line as below , but only get black line.
   from <a href="https://stackoverflow.com/questions/34932860/how-to-apply-a-texture-to-a-custom-geometry-in-three-js">how-to-apply-a-texture-to-a-custom-geometry-in-three-js</a>, I need set UV or write my own shade.
   But I am very new to three.js and webGL, not sure how to do it. 
   any help is welcome. Thanks.</p>
  
  <pre><code>loader.load('images/direction.png', function ( texture ) {
      texture.wrapS = THREE.RepeatWrapping;
      texture.wrapT = THREE.RepeatWrapping;
      texture.repeat.set( 40, 40 );
      var material = new THREE.MeshBasicMaterial({map: texture});
      var geometry = new THREE.Geometry();
      geometry.vertices.push(new THREE.Vector3(-10, 10, 0));
      geometry.vertices.push(new THREE.Vector3(-10, 20, 0));
      line = new THREE.Line(geometry, material);
      line.material.linewidth = 5;
  
      scene.add(line);
      renderer.render( scene, camera );
  }
  </code></pre>