[severak_cz]

Funny that this is practically the same concept as shooting in atelier with exterior background painted on walls as it was done in old movies. The progress is only in technology - now it's created by game engine and projected to giant LEDs, back then in 1930s it was done by hand by painters.

[estebank]

I think the innovation is the perspective correction of the background depending on the camera. That could have been accomplished with rear projection in film if it had been necessary by having the camera follow a preset path, but I don't think even BTTF attempted that.