The companies that created the hologram of Tupac Shakur that performed Sunday at Coachella aren’t saying much about how they did it.

But MyCoachella reader Ekke Tõnissoo pointed us toward a graphic Roxanne Palmer put together for International Business Times, which shows how Tupac was brought back to life by illustrating a Musion Systems patent based on an old theater trick. Palmer also notes that “hologram,” a term for a three-dimensional image, is actually a misnomer for Musion’s 2-D Tupac.

Also, the Los Angeles Times’ Deborah Netburn reported some new details today on how the late rapper’s image and voice were recreated:

Company spent four months creating virtual Tupac from video footage, photos
By Deborah Netburn
Los Angeles Times (MCT)

LOS ANGELES — The late Tupac Shakur rose again Sunday night at the Coachella Valley Music and Arts Festival — brought to life by James Cameron’s visual production house, Digital Domain, and two hologram-imaging companies, AV Concepts and the U.K.-based Musion Systems. The image joined headliners Snoop Dogg and Dr. Dre for two songs.

Dre is quiet about reports he’ll take the holographic Shakur on tour, and he’s asked Digital Domain and AV Concepts to refrain from telling the press too much about how they rendered the musician.

“He doesn’t want the magic spoiled for the people who will see it” during his set at the second weekend of the Coachella festival, a spokeswoman for Digital Domain told the Los Angeles Times.

Still, those familiar with special effects say the holographic Shakur was created using the same concept as an old magic trick, Pepper’s Ghost. The trick is to have a transparent piece of material that will reflect an image projected onto it while still allowing other people on the stage to move behind and in front of the image.

In the past, the transparent material was usually glass. For Sunday’s show, it was Mylar, a highly reflective, lightweight plastic, stretched on a clear screen customized by AV Concepts to descend onto the stage in seconds between sets of the performance.

If that makes the creation of a holographic Shakur seem easy, it’s not — especially because the performance was not based on archival footage. “This is not him performing at some point, this is completely original, exclusive performance only for Coachella and that audience,” Ed Ulbrich, chief creative officer at Digital Domain, told Bloomberg News.

And because Shakur was a real person with a devoted fan following, it was crucial to get all his mannerisms, tattoos and voice correct. The company created the virtual Tupac from video footage and photos of the rapper, working on the project for about four months.