An eye-popping hologram of murdered rapper Tupac Shakur has stolen the show at US music festival Coachella and amplified questions about the future of "live" performance. The high-definition projection of the gangsta rap icon appeared with superstars Snoop Dogg and Dr Dre in a stunning end to the first weekend of the annual music festival in California, setting off a wave of social media debate. Thousands in the crowd gasped as the shirtless Tupac - killed in a drive-by shooting in Las Vegas in 1996 - rose up on the stage. "What up, Coachella?" the digitally revived Tupac shouted before launching into his classic single Hail Mary. Amazingly life-like, down to his signature tattoos, Timberland boots and jewellery, the hologram stalked the stage, swapping phrases with Snoop Dogg and performing 2 of Amerikaz Most Wanted, Come With Me, and Gangsta Party. Then, Tupac's image dissipates. Digital Domain is behind the digitally altered images of Bra...