Fog display

A fog display or fog screen is a system that uses haze machines to create a semi-transparent wall, or
"curtain" of suspended particles which are illuminated by a projector, in order to produce a display
whose images seem to float
... in mid air. Several
commercial such systems
exist, such as FogScreen and Heliodisplay. This system can be expanded
using multiple projectors to
create a three-dimensional
image, thus becoming a volumetric 3D display