title: three.js rectAreaLight up to date
body: <p>So this abandoned? feature of three.js seems to have become somewhat of a holy grail; I've tried to implement it a couple of times unsuccessfully.</p>
  
  <p>The example working on an old release is here: <a href="https://threejs.org/examples/#webgl_lights_rectarealight" rel="nofollow noreferrer">https://threejs.org/examples/#webgl_lights_rectarealight</a></p>
  
  <p>My minimal broken example is here:
  <a href="https://jsfiddle.net/bitsofcoad/1k3arL33/" rel="nofollow noreferrer">https://jsfiddle.net/bitsofcoad/1k3arL33/</a></p>
  
  <pre><code>var width = 20;
  var height = 20;
  var rectLight = new THREE.RectAreaLight( 0xffffff, 500,  width, height );
  rectLight.intensity = 500.0;
  rectLight.position.set( 0, 30, 0 );
  rectLight.lookAt( mesh2.position );
  scene.add( rectLight )
  
  var rectLightHelper = new THREE.RectAreaLightHelper( rectLight );
  scene.add( rectLightHelper );
  </code></pre>
  
  <p>I have made sure to include the proper rectarealight library in the jsfiddle.</p>
  
  <p>This thread was particularly enlightening on the topic of why this PR had some difficulties:
  <a href="https://github.com/mrdoob/three.js/pull/9234" rel="nofollow noreferrer">https://github.com/mrdoob/three.js/pull/9234</a></p>
  
  <p>And this thread was interesting to see how far other people had gotten in developing a similar type of light for three.js:</p>
  
  <p><a href="https://stackoverflow.com/questions/17021264/improved-area-lighting-in-webgl-threejs">Improved Area Lighting in WebGL &amp; ThreeJS</a></p>
  
  <p>I don't really know what happened to break abelnation's example, or even if it is completely broken ( I may have screwed up my jsfiddle... ), but I think there is still considerable interest in this feature.</p>
  
  <p>The soft edges look so nice, I'm tempted to cannibalize WestLangley's custom shader (<a href="http://jsfiddle.net/hh74z2ft/89/" rel="nofollow noreferrer">http://jsfiddle.net/hh74z2ft/89/</a>), which has pretty much all the functionality I need.</p>
  
  <p>Anybody else able to get the basic functions working? Thanks!</p>