Facebook’s Mark Zuckerberg was an early believer in the prospect of virtual reality (VR) revolutionizing the way consumers interactive with content and one another. But that foresight hasn’t been enough to keep Facebook-owned Oculus Rift ahead of its competitors. Now that the field of VR platforms and headsets has widened considerably, Oculus is yielding significant market share over to the less expensive, and less expansive, competitors. Headset shipments are still pretty small but show signs of ramping up. An IDC report released in June estimates some 2.3 million units of VR and augmented reality (AR) headsets were shipped during the first quarter of 2017, but expects to see triple-digit growth in shipped units during the second half of the quarter,…