While I'm continuing to repost things I've already released, here's an article I wrote in the middle of last year when the Duke Nukem Forever 2001 prototype leaked out that examines how that trailer was made, and other magic tricks. It also contains exactly zero images of the actual prototype because nobody was sure exactly how much shit the Ever Dreaded Paralegals were willing to permit.
E3 stage demos are all, universally, to a letter, an Utter Fucking Shitshow behind the scenes. All hurriedly put together in a few weeks of the most brutal of crunchtimes to sell an idea, a vision of what a finished product will be, to a theater-load of jaded journalists and bored investors, to say nothing of the many thousands more watching via live-streams or post-show video recordings. An interjection into development schedules that poses the impossible, paradoxical task of showcasing features that haven’t actually been built yet through some combination of pre-scripted cutscenes pretending to not be cutscenes and well-rehearsed play-acting by the increasingly-nervous developer on-stage making sure to hit their marks just right.
Here's that link again, but in lame embed format: