But before that can happen, augmented-reality devices still face many obstacles. Chief among them: packing their hardware into a wireless, light-weight headset, about the size and cost of an expensive pair of sunglasses. In other words, the question is no longer if holographs can blend with reality, but how, how well, and at what price.

“I’ve tried everything that’s on the market and I still think we have a long way to go,” Wetzstein said. “If Magic Leap delivers what they promise, it will be a significant improvement. However, AR faces a lot of challenges, because the devices need to be so small and low power, and there’s a lot of challenges with optics, electronics, vision.” Augmented-reality displays must be graphically robust and deliver “an amazing visual experience” while at the same time being small, comfortable, and portable enough that people would want to wear them, Wetzstein explained.

Technology Review’s Rachel Metz, who had the opportunity to try both devices this winter, wrote that Magic Leap’s target prototype size could not show her the same quality of images as the larger optometrist-sized version of the headset. She also noted that while HoloLens showed off a fully mobile headset at Build, it’s unclear whether Magic Leap has fit its tech into a wearable size.

“A lot of these digital miracles all come down to a common culprit: power,” said David Whittinghill, an assistant professor of computer graphics at Purdue who’s interested in developing for these devices. “How do you get the batteries to power these sort of video-records? How are you going to miniaturize it? How do you make it mobile and get it down to a weight that people can carry around?” As Wetzstein and others pointed out, for an augmented-reality device to be wearable in everyday life it also needs a bright enough display to work outdoors. But then again, better brightness takes up more battery.

There’s also the problem of creating realistic illusions in the first place, and fitting them naturally into the clutter of objects already in our spaces. In a head-mounted device, any slight misalignment or lag-time with its projections might make people sick—a little glitch and the device is too annoying; a major mismatch and it’s dysfunctional. This is where computer vision comes in: The headwear has to know where and what the eye is looking at, and the device must sense what’s in the real world, what’s moving and what’s staying still.

But even when virtual images successfully align with the physical world, and the devices achieve a comfortable size, augmented reality’s viewing experience is still likely to be trumped by virtual reality’s wider field of view. While the demos show fully immersive augmented experiences, the actual headset’s capabilities remain in a somewhat smaller window. Reporters at the Microsoft Build Developer Conference noted that images kept dropping out of the HoloLens field of view, an area that spans about 40 degrees, according to an estimate in Wired. Some described the HoloLens’ narrow viewing area—about the size of a TV—as shattering the experience’s illusion, whereas others found these “glimpses of the unenhanced world on the periphery” to be a persistent distraction. The Verge’s Adi Robertson explained that anything that slipped outside this window disappeared, rendering peripheral vision useless. Alice Truong at Quartz called the HoloLens limited perspective the “AR version of tunnel vision.”