Category Archives: Mixed reality

My day with Windows Insider Preview, Unity 2017.2.0b8 and Windows Mixed Reality Headset

Yes, I am drinking a beer right now – it has been a long day. Mostly I seemed to spend it nursing Windows through its upgrade to the latest Insider Preview (16257) and begging the Insider Preview website to allow me to download the Insider Preview SDK which seemed to require all kinds of things done right and the wind blowing in the right direction at the same time.

The somewhat bizarre screen capture above is from a scene I created in the default room. The hologram figures are animated incidentally. What I mostly failed to do was to get existing HoloLens apps to run on the MR headset as Unity kept on reporting errors when generating the Visual Studio project for the apps, after having performed every other stage of the build process correctly. Very odd. I did manage to get a very simple scene with a single cube working ok, however.

Then I went back to the production version of Windows (15063) and tried things there. Ironically, my HoloLens app worked (apart from interaction) on the MR headset using Unity 5.6.2.

Clearly this particular Rome wasn’t built in a day – a lot more investigation is needed.

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Spatial maps – the next valuable currency

Fascinating and thought provoking article here about iRobot’s reported plan to monetize the spatial maps created by Roombas. Time and time again in my career (including right now) there has been a need for accurate spatial maps. Once only accessible to high-end robots outfitted with Lidars, now almost anything that moves is capable of generating and refining spatial maps.

This fits very nicely with the idea that mixed reality glasses will become ubiquitous. Imagine walking into a new space and getting a spatial map automatically downloaded from the cloud. No need to ask where the restrooms are any more! This kind of capability would be of benefit to almost any enterprise. For example, check into a hotel and the spatial map with directions to your room gets downloaded to your glasses.

There are three parts to this puzzle – mapping, storage and delivery. Once all these become ubiquitous, not having access to this data or MR glasses will seem very odd indeed. Of course, selling data about private houses is not something that should be allowed without the owner’s explicit permission but making the data available to the owner would have tremendous value. There’s going to be a whole new type of specialist – the virtual interior designer. Unless you need to interact with something physically, why bother having the real object rather than a virtual version of it?

Of course there’s always the chance that some company gets the data and has some software that can detect if your floor plan has space for one of their products. In some kind of bizarre world the product could appear virtually in the space with a link to where you could buy it. This would be real/virtual product placement! What a ghastly prospect :-(.

Second version of HoloLens HPU – separating mixed reality from the cloud

Some information from Microsoft here about the next generation of HoloLens. I am a great fan of only using the cloud to enhance functionality when there’s no other choice. This is especially relevant to MR devices where internet connectivity might be dodgy at best or entirely non-existent depending on the location. Putting some AI inference capability right on the device means that it can be far more capable in stand-alone mode.

There seems to be the start of a movement to towards putting serious but low power-consuming AI capability in wearable devices. The Movidius VPU is a good example of this kind of technology and probably every CPU manufacturer is on a path to include inference engines in future generations.

While the HoloLens could certainly use updating in many areas (WiFi capability, adding cellular communications, more general purpose processing power, supporting real-time occlusion), adding an inference engine is certainly extremely interesting.

Mixed Reality and the missing fourth dimension

The screen capture above is a scene from a HoloLens via mixed reality capture (MRC) showing four virtual rings with different levels or brightness. The top left is 100% red, the bottom right black and the other two are intermediate levels of brightness.

The photograph above was shot through a HoloLens and is a reasonable representation of what the wearer actually sees. Unsurprisingly, since all see-through MR headsets work by overlaying light on the real scene, the black ring has vanished and the intermediate brightness rings become transparent to some degree based on the relative brightness to the real world scene.

This is a considerable obstacle for inserting realistic virtual objects into the real world – if they are dark, they will be almost transparent. And while indoors it is possible to control ambient lighting, the same is certainly not true outdoors.

What is needed is not just support for RGB but RGBA where A is the fourth dimension of color in this case. The A (alpha) value specifies the required transparency. The Unity app running on the HoloLens does of course understand transparency and can generate the required data but the HoloLens has no way to enforce it. One way to do this would be to supplement the display with an LCD that acts as a controllable matte. The LCD controls the extent to which the real world is visible at each display pixel while the existing display controls the color and intensity of the virtual object. No doubt there are significant challenges to implementation but this may be the only way to make see-through MR headsets work properly outdoors.

Mixed reality: does latency matter and is it immersive anyway?

I had a brief discussion last night about latency and its impact on augmented reality (AR) versus virtual reality (VR). It came up in the context of tethered versus untethered HMDs. An untethered HMD either has to have the entire processing system in the HMD (as in the HoloLens) or else use a wireless connection to a separate processing system. There’s a lot to be said for not putting the entire system in the HMD – weight, heat etc. However, having a separate box and requiring two separate battery systems is annoying but certainly has precedent (iPhone and Apple Watch for example).

The question is whether the extra latency introduced by a wireless connection is noticeable and, if so, is it a problem for AR and MR applications (there’s no argument for VR – latency wants to be as close to zero as possible).

Just for the record, my definition of virtual, augmented and mixed reality is:

  • Virtual reality. HMD based with no sense of the outside world and entire visual field ideally covered by display.
  • Augmented reality. This could be via HMD (e.g. Google Glass) or via a tablet or phone (e.g. Phab 2 Pro). I am going to define AR as the case where virtual objects are overlaid on the real world scene with no or partial spatial locking but no support for occlusion (where a virtual object correctly goes behind a real object in the scene). Field of view is typically small for AR but doesn’t have to be.
  • Mixed reality. HMD based with see-through capability (either optical or camera based) and the ability to accurately spatially lock virtual objects in the real world scene. Field of view ideally as large as possible but doesn’t have to be. Real time occlusion support is highly desirable to maintain the apparent reality of virtual objects.

Back to latency and immersion. VR is the most highly immersive of these three and is extremely sensitive to latency. This is because any time the body’s sensors disagree with what the eyes are seeing (sensory inconsistency) is pretty unpleasant, leading rapidly to motion sickness. Personally I can’t stand using the DK2 for any length of time because there is always something or some mode that causes a sensory inconsistency.

AR is practically insensitive to latency since virtual objects may not be locked at all to the real world. Plus the ability to maintain sight of the real world seems to override any transient problems. It’s also only marginally immersive in any meaningful sense – there very little telepresence effect.

MR is virtually the same as AR when it comes to latency sensitivity and is actually the least immersive of all three modes when done correctly. Immersion implies a person’s sense of presence is transported to somewhere other than the real space. Instead, mixed reality wants to cement the connection to the real space by also locking virtual objects down to it. It’s the opposite of immersion.

Real world experience with the HoloLens tends to support the idea that latency is not a terrible problem for MR. Even when running code in debug mode with lots of messages being printed (which can reduce frame rate to a handful of frames per second) isn’t completely awful. With MR, latency breaks the reality of virtual objects because they may not remain perfectly fixed in place when the user’s head is moving fast. But at least this doesn’t generate motion sickness, or at least not for me.

There is a pretty nasty mode of the HoloLens though. If the spatial sensors get covered up, usually because it is paced on a table with things blocking them, the HoloLens can get very confused and virtual objects display horrendous jittering for a while until it settles down again. That can be extremely disorientating (I have seen holograms rotated through 90 degrees and bouncing rapidly side to side – very unpleasant!).

On balance though, it may be that untethered, light weight HMDs with separate processor boxes will be the most desirable design for MR devices. The ultimate goal is to be able to wear MR devices all day and this may be the only realistic way to reach that goal.

HoloLens Spectator View…without the HoloLens


I’ll explain the photo above in a moment. Microsoft’s Spectator View is a great device but not that practical in the general case. For example, the original requires modifications to the HoloLens itself and a fairly costly camera capable of outputting clean 1080p, 2k or 4k video on an HDMI port. Total cost can be more than $6000 depending on the camera used. My goal is to do much the same thing but without requiring a HoloLens and at a much lower cost – just using a standard camera with fairly simple calibration. Not only that, but I want to stream the mixed reality video across the internet using WebRTC for both conventional and stereo headsets (such as VR headsets).

So, why is there a HoloLens in the photo? This is the calibration setup. The camera that I am using for this Mixed Reality streaming system is a Stereolabs ZED. I have been working with this quite a bit lately and it seems to work extremely well. Notably it can produce a 2K stereo 3D output, a depth map and a 6 DoF pose, all available via a USB 3 interface and a very easy to use SDK.

Unlike Spectator View, the Unity Editor is not used on the desktop. Instead, a standard HoloLens UWP app is run on a Windows 10 desktop, along with a separate capture, compositor and WebRTC streamer program. There is some special code in the HoloLens app that talks to the rest of the streaming system. This can be present in the HoloLens app even when run on the HoloLens without problems (it just remains inactive in this case).

The calibration process determines, amongst other things, the actual field of view of the ZED and its orientation and position in the Unity scene used to create the virtual part of the mixed reality scene. This is essential in order to correctly render the virtual scene in a form that can be composited with the video coming from the ZED. This is why the HoloLens is placed in this prototype rig in the photo. It puts the HoloLens camera roughly in the same vertical plane as the ZED camera with a small (known) vertical offset. It’s not critical to get the orientation exactly right when fitting the HoloLens to the rig – this can be calibrated out very easily. The important thing is that the cameras see roughly the same field. That’s the because the next step matches features in each view and, from the positions of the matches, can derive the field of view of the ZED and its pose offset from the HoloLens. This then makes it possible to set the Unity camera in the desktop in exactly the right position and orientation so that the scene it streams is correctly composed.

Once the calibration step has completed, the HoloLens can be removed and used as required. The prototype version looks very ungainly like this! The real version will have a nice 3D printed bracket system that will also have the advantage of reducing the vertical separation and limit the possible offsets.

In operation, it is required that the HoloLens apps running on both the HoloLens(es) and the desktop are sharing data about the Unity scene that allows each device to compute exactly the same scene. In this way, everyone sees the same thing. I am actually using Arvizio‘s own sharing system but any sharing system could be used. The Unity scene generated on the desktop is then composited with the ZED camera’s video feed and streamed over WebRTC. The nice thing about using WebRTC is that almost anyone with a Chrome or Firefox browser can display the mixed reality stream without having to install any plugins or extensions. It is also worth mentioning that the ZED does not have to remain fixed in place after calibration. Because it is able to measure its pose with respect to its surroundings, the ZED could potentially pan, tilt and dolly if that is required.