Retrofitted 3D

Following our visit to the iMax theatre, Wilson has just told me he's thinking of releasing Titanic: The Film in 3D. 

I started to explain about twin-lens cameras and inter-ocular distances, but W stopped me, saying, 'It's okay, New Dad - I know how it's done! I took off the 3D glasses during the film, and it's just a trick. Look, you put on the so-called "special" glasses, but really they're just sunglasses; they make the picture so dim that you can't tell whether you're watching 2D or 3D! And without them on, the picture looks like this!' He showed me this 3D-ised frame from his film.  'Anyway, Mr James Cameron's film wasn't shot in 3D either, he did it all afterwards!'

I do have some doubts about this.