The auditorium is filled with a vapourised substance. Water vapour might do. It just needs to be a) harmless b) as imperceptible as possible and c) with the ability to hold a small nanobot in each droplet.

So you end up with an auditorium filed with harmless, imperceptible nanobots. A wifi signal is ten received by each of these bots, which tell it whether to glow or not, and if so what colour, depending on where it is in the cinema.

Hey-and-indeed-presto, a hologram will appear in 3D above the audience.
-- percy, Mar 08 2013

sounds like a scifi device rather than something that could be cobbled together now.

So what do you do for scripts that start off "The sun was shining..."
-- FlyingToaster, Mar 08 2013


You could do this on a larger scale with a swarm of helium balloons.
-- MaxwellBuchanan, Mar 08 2013



random, halfbakery