When you stick your bare, clumsy, flesh-suit hands into a virtual world, the physics engine reacts like an immune system trying to purge antibodies. What is this? How do I manipulate it? It doesn't fit here, get out!
Leap Motion's newly-launched beta of Interaction Engine operates as a layer between human elements and their Unity game engine. When hands show up, it employs an "alternate set of physics rules" to adjust to natural interaction with virtual objects. Gripping, stacking, holding, and throwing get easier and more fluid.
The before and after demonstrations are like a cheesy As Seen On TV infomercial:
Developers can access Interaction Engine 101, an example project and open source code to model their own Oculus and Vive projects, on Github.