title: Three.js blend envmap with semi transparent texture
body: <p>I have a plane with a MeshBasicMaterial and a cubecamera. I assign the cubecamera.renderTarget as an envmap to my material and a png image as a texture for my material. The png image is pransparent execept the center of it. What I would like to accomplish is to have the reflection - cubecamera envmap be visible only where the png is transparent.</p>
  
  <p>Is this possible? and if so please guide me through because I'm new with three.js.
  Currently my material looks like this:</p>
  
  <pre><code>productMaterial = new THREE.MeshBasicMaterial( {
      map: productModelTexture,
      envMap: that.cubeCamera.renderTarget,
      combine: THREE.MixOperation,
      reflectivity: 0.25,
      color: that.models.settings.color,
      specular: that.models.settings.specular,
      side: THREE.FrontSide,
      transparent: true,
      fog: false
  } );
  </code></pre>