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Acer Mixed Reality HMD Doesn’t Do Mixed Reality

As far as we can tell, and as far as Acer would say, the company’s mixed reality HMD is actually just a VR HMD with inside-out tracking.

We’ve been clamoring for more information (any solid information, really) on Acer’s upcoming mixed reality HMD specifically, and any of the other supposedly upcoming XR HMDs from other PC makers generally, but so far any details have been sparse. We learned a bit about the Acer HMD at GDC, but...not much. At Acer’s NYC event, we learned a little more. And it was a mixed bag. (You can read about our hands-on time with the HMD here.)

It’s Tethered, But Does Inside-Out Tracking

First and foremost, we can confirm that this device is tethered. In this case, that means it does not have its own onboard CPU, GPU, RAM, and storage. Instead, it connects to a PC via a combo HDMI/USB cable. (That PC will need at least the baseline specs detailed here.) It does, however, provide inside-out, 6DoF tracking.

The fact that it’s tethered pops the bubble of hope that Microsoft and its partners figured out a way to build “HoloLens lite” XR HMDs. Instead, it’s more like a cheaper version of the Vive and Rift. (This was not unexpected, but given the name of the device, we had hoped for the former.)

However, the presence of inside-out tracking is a big deal and in a way puts these commodity-level HMDs (or at least, this one in particular) a step above the Vive and Rift, which rely on outside-in tracking for room scale movement.

Inside-out tracking is one of the next holy grail features that the industry needs on VR HMDs. At its best, it provides a world-scale XR experience, like the HoloLens. But it’s also a step up from the outside-in tracking that the Vive and Rift require to achieve room scale tracking. With outside-in tracking, mounted sensors have to be able to “see” the headset. If you move your head in such a way that the sensors lose track of the headset, the immersion is cracked.

An HMD with inside-out tracking, by contrast, moves with you (the HMD wearer).

“Essentially” HoloLens Inside-Out Tracking

How does the Acer HMD accomplish its inside-out tracking? It uses “essentially” the same tracking as the HoloLens. (“Essentially” is the word a rep used to describe it.)

We’re going to have to connect some dots here, but we can start with a few things we know. First of all, we know how HoloLens does its inside-out tracking (scroll to the “Sensors Sensing Sensibly” section, and yes, we still like that subhead).

For those who don’t feel like clicking that link, here’s the section:

The sensor bar on the HoloLens comprises four “environment understanding cameras,” two on each side; a depth camera; an ambient light sensor; and a 2MP photo/HD video camera. Some of these are off-the-shelf parts, whereas Microsoft custom-built others.The environmental sensing cameras provide the basis for head tracking, and the (custom) time of flight (ToF) depth camera serves two roles: It helps with hand tracking, and it also performs surface reconstruction, which is key to being able to place holograms on physical objects. (This is not a novel approach--it’s precisely what Intel is doing with its RealSense 400-series camera on Project Alloy.)These sensors work in concert with the optics module (described above) and the IMU, which is mounted on the holographic lenses, right above the bridge of your nose.Said the presenter, “Environment cameras provide you with a fixed location in space and pose,” and the IMU is working fast, “so as you move your head need to be able to feed your latest pose information into the display as quickly as possible.” He said that HoloLens can do all of this in <10ms, which, again, is key to preventing “swimming” and also to ensuring that holograms stay locked to their position in the real world space.

Looking at the Acer HMD, the sensor bar doesn’t seem to have all of the above. You can see two cameras, but nothing else. We now know that those are depth tracking cameras. There could be more good stuff hidden behind that black bar, but we don’t know for sure at this time.

We also know that the Acer mixed reality HMD has an accelerometer, gyroscope, magnetometer, and proximity sensor.

What Kind Of Reality?

In a demo, we saw that at the very least the Acer mixed reality HMD has no passthrough capabilities, and it’s a fully occluded headset, so you can’t see through the lenses, either. It also doesn’t do any sort of “merged reality” like Intel’s Project Alloy does. What it uses the inside-out capabilities for is room scale tracking and a chaperone-like system that throws up a warning when you get too close to a wall or other physical object.

To us, that means this is not a mixed reality HMD; it’s a virtual reality HMD.

At this point, we’re getting into the weeds of terminology, but words are important. Technically speaking, the entire spectrum of “reality” with these devices ranges from VR (fully occluded, environments entirely rendered) to AR (see through lenses with some elements added). And that spectrum is known as “mixed reality.”

In that sense, this Acer device could be classified as “mixed reality,” in the same way that the Rift, Vive, HoloLens, et al, are “mixed reality.” Microsoft and Acer would assert that any device that provides a simulated environment that acknowledges the real world--in this case, it digitizes physical barriers by detecting them and warning you that you're in proximity--counts as mixed reality. Further, to be fair, the Windows Mixed Reality platform supports actual MR technology, such as object/hand tracking and camera passthrough capabilities--even though this Acer device does not.

But we would argue that for end users, that’s misleading, and it’s why we’ve been careful to use precise and general terminology where applicable. It’s why we call Rift and Vive “VR,” why we don’t call 360-degree cameras that can’t shoot in 3D “VR,” and why we’ve adopted the term “XR” to describe the whole of the aforementioned mixed reality spectrum.

Regardless whether the Acer mixed reality headset has an accurate name or not, this is not the mixed reality headset you were looking for.