As expected, last night a hologram of deceased rapper Tupac Shakur wowed crowds at Coachella, and now a video of the spectacle has surfaced on YouTube. It's a tall order, reanimating corpses, but the performance of Tupac's "Hail Mary" was incredibly lifelike. So how was it done?

The performance reportedly used the same technology that enabled Mariah Carey to perform a concert in five cities simultaneously. Executing the Carey illusion relied on both modern day techniques and an old magician's trick dating back to the 19th Century. First, a video was composed by SFX company MPC using a mixture of live footage, wire-framing, and CGI. This was then fed into Musion's holographic technology, which projects the image onto a special foil. The foil is based on principles set out in the old magician's illusion Pepper's Ghost, which trick audiences into thinking they're viewing a person or object rather than a simple reflection. By using a lightweight foil which mimics the properties of semi-transparent glass, Musion is able to extend the concept's scale without limiting the efficacy of the illusion. The results, as you can see in the video below (warning, NSFW language) are pretty spectacular.

Impressive though it may be, it's not quite perfect. The projection on stage often moves while the figure is stationary, leading to a "moonwalking" effect (how long before we see a Michael Jackson performance recreated in this way?). There are also some issues with lighting and the movement of the specter in general, which often appears to be little more than CGI. There's also the question of taste. While the Mariah Carey concert was obviously agreed on by the artist, how could Tupac be complicit in last night's performance? You have to wonder if it's ethically right to have a deceased artist endorse an event in this way — having Tupac shout "what the f--- is up Coachella" doesn't sit quite right with us.

Update: Although the techniques used and final product are very similar, the companies detailed in this report relate to the aforementioned production of the Mariah Carey hologram. According to MTV, the Coachella performance was put together by Digital Domain and AV Concepts, who license Musion's holographic technology for use in the US.