code: public void makeSceneSelectable(GVRScene scene) {
          if (this.scene == scene) {
              //do nothing return
              return;
          }
  
          //cleanup on the currently set scene if there is one
          if (this.scene != null) {
              //false to remove
              updateCursorsInScene(this.scene, false);
          }
  
          this.scene = scene;
  
          if (scene == null) {
              return;
          }
          // process the new scene
          for (GVRSceneObject object : scene.getSceneObjects()) {
              addSelectableObject(object);
          }
          //true to add
          updateCursorsInScene(scene, true);
      }
docs: Use this call to make all the {@link GVRSceneObject}s in the provided GVRScene to be
  selectable.
  <p/>
  In order to have more control over objects that can be made selectable make use of the
  {@link #addSelectableObject(GVRSceneObject)} method.
  <p/>
  Note that this call will set the current scene as the provided scene. If the provided
  scene is same the currently set scene then this method will have no effect. Passing null
  will remove any objects that are selectable and set the scene to null
  
  @param scene the {@link GVRScene} to be made selectable or <code>null</code>.