This hack is actually a stereolithography rig, which is a kind of 3D printing which will cure solid parts of a liquid resin. You can check out the YouTube video of it in action after the jump, but before that, a little bit of explanation on how it works is in order.
Stereolithography will fire an UV laser into a vat of liquid plastic resin, where said laser is able to cure the resin into a solid, while the computer program helps guide the path of the laser in a manner that helps it shape a solid 3D object out of the liquid. This is still a work in progress, and a perfected version should be heading your way in due time.