If there’s one trend that’s poised to take off and enter the mainstream in 2012, it’s 3D printing. Sometimes referred to as additive manufacturing, 3D printing is the process of taking computer-generated designs and building them up in the real world, layer by layer, using materials such as plastic or powdered metal, via printers the size of a desktop. In the same way that you might print out a paper document, you can now print out a beautifully-designed piece of jewelry, a dress, an industrial part, a door hinge -- almost anything you can imagine -- even a Stradivarius violin.