In all the hoopla that surrounded Sony’s PlayStation 4 conference, the creators of Little Big Planet showed off a newfangled tech demo that lets players sculpt statues, which vaguely look like the Venus of Willendorf. Judging from what was shown, you take a Move motion-controller and dutifully sketch into thin air. Your “sculpture,” which is actually just a piece of digital art, appears on the television. You can rotate it. Enter the 3D Doddler, a pen that lets you draw in actual 3D space, invented by two guys from Boston. Drawing something in 3D is hard to phantom if you’ve…