During a Sunday performance by rap stars Dr. Dre and Snoop Dogg, an incredibly realistic hologram of the long-dead Tupac Shakur joined them on stage, setting the crowd, and the Internet, buzzing with excitement.

The trio played Tupac's classic tracks "2 Of Amerikaz Most Wanted" and "Gangsta Party" as social media networks lit up with talk about Tupac's return, 15 years after his death.

The rapper appeared on stage through the use of a technology similar to the projection systems that gave birth to Japanese pop star Hatsune Miku, a cartoon that sings and dances live on stage. U.S. art-pop group The Gorillaz used the same technology to have their animated characters appear on stage.

Some will be sad to learn, however, that the 3D effect is a trick of perspective and not quite "Star Trek" yet. A digital light processing (DLP) projector beams an image from above onto a transparent, flat surface held at an angle, rendering an image that appears to be three dimensional. A similar trick is being developed for use with business teleconferencing.

The tech is implemented by Dimensional Studios, which calls its projection display "Musion Eyeliner." It's been used for a variety of stage shows and events, like Al Gore's "Live Earth," the Grammy Awards and various other corporate events.

Producers of Sunday night's show likely either cut Tupac's performance out of a previously recorded video and rendered it on a larger scale, or they used computer graphics to render Tupac's face and body onto the movements of another performer. Either way, the end result was very effective.

A video explaining how it works follows, below.

This video was published to YouTube on Sunday, April 15, 2012. It contains adult language.

This video is from New Scientist.