Hehe. I think I can explain how this was done...because I made it:
Giant Robots! : Ryan Nagata
I did that video over the course of an afternoon. It was tremendously easy except for having to repaint the false ground every few minutes to match the changing light. I was inspired by an FX guy I met named Rocco Gioffre (
Rocco Gioffre - IMDb). He showed me some forced perspective stuff that really blew my minds when I visited his FX house.
He does some of the biggest movies nowadays, but his credits go all the way back to Blade Runner. Rocco's all about using EVERY tool at his disposal, whether it be physical models, 3d models, or 2d matte paintings. He often scoffs at the idea of using 3d models for certain shots when they could have been done 10 times cheaper, better, and faster using more traditional methods. Not that he doesn't use the latest technology when it's the right tool for the job. It's really a case by case thing.
Yes, this is a very cool use of perspective and models, but the application is fairly limited to static shots with almost no human interaction. (The running gag is about as much as you'll be able to do.)
Believe it or not, you're not limited to static shots with forced perspective. There is a technique that I've always wanted to try but never got around to where you can incorporate pans and tilts into forced perspective shots. Basically, you need a tripod mount that will allow you to slide the camera back so that the film plane lies directly over the axis of rotation of the head. When you do that, you eliminate all parallax between the foreground and background. So you can pan the camera and the forced perspective illusion is maintained.
This technique was actually used in the shot that Rocco showed me that really blew my mind. I think it was from the Young Sherlock Holmes series. There was a dolly shot that followed a character down a wall and then panned around as he turned into an alleyway. The alleyway was actually a miniature model that was only a few feet in front of the actor. They didn't have the budget to build a full, period alleyway. So this was essentially built in someone's backyard. But you would NEVER know it. It was totally seamless.