once done on the set, the all cgi crew will have for mission to past the actors on the digital world, to cut out the blue screen, to add digital light, the all climatic effects, the reflection...3d compositing and 2D ones, to add the all sound (only voices reccorded on set) ect... a titant work and maybe the only purpose to see it, to respect the time and work done... its certainly a film you go to see for the process.