A technique that has been around for the better part of a century, rear projection is a way for filmmakers to collapse space and time to create the illusion of a vibrant, epic background (without the epic budget). It has been used in all kinds of ways with all different kinds of films, from monster movies to melodramas, to amazing effect, though it really came to be a defining feature of the noir genre. Now no longer the cutting-edge of technological innovation, it is still used from time to time in films like The Love Witch, now as an intentional artistic quote rather than a clever camera trick.