Draw a line in threejs

scene-draw-line.js

// creates a white (!!) line from 0,0,0 to 300,0,0
// make sure background is other color than white ;)
var geometry = new THREE.Geometry();
geometry.vertices.push(new THREE.Vector3(0, 0, 0));
geometry.vertices.push(new THREE.Vector3(300, 0, 0));

var line = new THREE.Line(
  geometry, 
  new THREE.LineBasicMaterial( { color: 0xffffff, linewidth: 1 } )
);

this.scene.add(line);