"Recent developments in computers and computer graphics have made spatial 3-D images more practical and accessible," the patent application explains. "The computational power now exists, for example, for desktop workstations to generate stereoscopic image pairs quickly enough for interactive display."

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The patent application goes on to assert that two-dimensional projections of 3-D scenes are inadequate. "Without the benefit of 3-D rendering, even high quality images that have excellent perspective depictions still appear unrealistic and flat," it says.

It identifies the shortcomings of existing 3-D display techniques, noting that they may require a viewer to remain in a fixed position, to wear polarized glasses, or may fail to render shapes so that they appear to have the same volume and density at different viewing angles.

Thus the patent application goes on to describe a projection display system that renders images in three dimensions while still allowing viewers freedom of movement. It proposes to achieve this effect by tracking the position of the viewer(s).

"No headgear needs to be worn by the observer," the patent application explains. "In one embodiment, the system of the present invention provides a stereoscopic 3-D display and viewing experience; in another, it delivers a realistic holographic 3-D display experience."

As is the case with any patent application, there's no guarantee Apple will ever commercialize this technology. Before it does, graphics cards will have to incorporate a stereoscopic rendering engine.