Taking the audience into the movie.
http://www.artmuseum.net/w2vr/timeline/Heilig.html
Morton Heilig | Sensorama
In the 1950's it occurred to cinematographer Morton Heilig that all the sensory splendor of life could be simulated with "reality machines." He proposed that an artist's expressive powers would be enhanced by a scientific understanding of the senses and perception. His premise was simple but striking for its time: if an artist controlled the multi-sensory stimulation of the audience, he could provide them with the illusion and sensation of first-person experience, of actually "being there."
Inspired by short-lived curiosities such as Cinerama and 3D movies, it occurred to Heilig that a logical extension of cinema would be to immerse the audience in a fabricated world that engaged all the senses. He believed that by expanding cinema to involve not only sight and sound, but also taste, touch, and smell, the traditional fourth wall of film and theater would dissolve, transporting the audience into a habitable, virtual world. He called this cinema of the future "experience theater," constructing a quirky, nickelodeon-style arcade machine in 1962 he aptly dubbed Sensorama, that catapulted viewers into multi-sensory excursions through the streets of Brooklyn, as well as other adventures in surrogate travel.