A great explanation. Full story at Westword:

In essence, the process involves taking high-def images and projecting them onto Mylar film that is positioned at a 45 degree angle to create images that appear to be three-dimensional: “You’re driving down the freeway, and you have a pack of cigarettes laying on the dash of your car,” explains Nick Smith, AV Concept’s co-founder, “reflects up and it looks like the cigarettes are floating above your hood in front of you. It’s a light technology with a reflective technology. The light reflects the image back into something that makes it look like it’s standing up. Your windshield raised at an angle like that creates that same effect.”

And in case you haven’t seen it yet, skip to the 17-minute mark below:

Dr. Dre & Snoop Dogg (Live at Coachella, 2012)... by coachellasets