Volumetric displays are 3d displays, and developments in this technology remain in a very early stage. The depth of the image is perceived by the naked eye, so no special glasses are needed to see the dimensionality.
They can be divided into two categories: swept volume displays and static volume displays. The main difference between one and the other is that in the swept volume displays use a rotating solid (usually a mirror) where many images are projected so fast to that your eyes can build up a 3d image using the ‘slices’. The static volume displays rely on a 3d volume of active elements, which can be called voxels. They change color to display a point in that 3d location or voxel (it is analogous to a pixel, a volumetric pixel), which will help you render the mental image. An example of static volume displays are laser plasma technology displays.
It is hard to find examples of volumetric displays which are not oriented to advertising a brand or product. Current applications tend to use them as output-only devices mainly for this purpose. One of the interesting opportunities that this type of display system brings is 3d interaction. Simple gestures can be perceived, like is the case with Sony’s 360º display. We can move and interact with the object using handmotion. It is also possible to play special volumetric 3d videogames.
An important aspect to note about the interactivity potential is that virtual reality environments conceive virtual objects that can be at a very large distance from the user’s virtual position, whereas all virtual objects in a volumetric display are always within the arm’s reach of an user. Another example of a volumetric and interactive display system was also shown last year at the 2010 Siggraph. ‘N00tron’ is based on a spinning bicycle wheel and uses Monkeylectric display hardware.
It is a big pity that until the technology is not out of the lab and easily-affordable it remains as a long-distant possibility with a big potential for interactivity and visual artists.