Digital Healthcare, Augmented Reality, Mobile Apps and more! Andreas Jakl is a professor @ St. Pölten University of Applied Sciences, Microsoft MVP for Windows Development and Amazon AWS Educate Cloud Ambassador.
Did you follow the blog post series on setting up Spectator View for HoloLens? The following issues frequently occurred when testing Spectator View. To make your life easier, make sure you check these troubleshooting tips & tricks:
HoloLens Sharing Offset
Between your two HoloLenses, there can be some offset in the placing of the holograms. In one HoloLens, you can for example position your hologram directly on the table; on the second HoloLens, it’s one meter next to the table.
In the final part of the HoloLens Spectator View series, I’ll add the final tweak to my sample project and show you what kind of photos the Compositor saves on your PC. Getting to this point has taken a lot more work than expected (+ a lot more blog posts, too!), but the journey was worth it! You can finally get great photos and videos of the mixed reality experience on HoloLens.
Script Execution Order
Sending the updates didn’t work right away, so I searched for other changes that the sample does differently from my app that might be responsible. One such case was the Script Execution Order.
In Unity, the order in which scripts are initialized is arbitrary. When debugging, I found an issue that an instance of a class wasn’t available yet when a script wanted to access it.
To make Spectator View work in our own HoloLens project, we actually have to understand how it’s working, what it is doing and how it is related to the HoloLens Sharing Experience. Turns out that there is a lot to do in our app (including transmitting custom messages) to prepare it for the full Spectator View experience!
Synchronizing Objects: Anchor & SceneManager
The Spectator View is based on the Sharing experience of the HoloToolkit, but it contains its own “fork” of the code. Instead of us having to manually decide & code which objects and interactions to send via network messages (as in the normal Sharing use case), the fork of the Spectator View transmits some data by default to our DSLR-mounted HoloLens.
However, it’s important to understand that if you use Spectator View, you also need to integrate most of the Sharing code. Essentially, a lot of code is duplicated between the two frameworks, with only slight differences in order to give the DSLR-mounted HoloLens a special role, plus the PC running Unity also needs to connect in order to correctly render the scene.
With the first Bluetooth 5 devices just released (first and foremost the Samsung Galaxy S8), Bluetooth Beacons like Apple iBeacon and Eddystone by Google gain a lot of potential. Increased range means future beacons will cover a much larger area, without increased power consumption. With the payload increase of beacon advertisement frames from 31 bytes to 255 bytes, the amount of information transmitted by beacons can substantially increase.
In my session about Bluetooth Beacons at the Mobile Developer After-Work #14: Creating Immersive Environments, I provided a short update about the latest news. Unfortunately, recording of the live session at the event failed. Therefore, I’ve re-recorded it – you will miss the live experience, but I did have a little more time for more detailed explanations of some important facts, so it’s well worth watching again even if you have been at the #mdaw14 Event!
In the previous part, we’ve re-compiled Spectator View using the latest HoloToolkit sources. At the time of writing, this resulted in a compile error, as the HoloToolkit for Unity has seen a breaking change since Spectator View was released.
In this part, we’ll first fix the Spectator View code, and then set it up correctly in our own Unity scene. Then, we’ll need to check several other things: how to launch the Sharing Service, adding Internet Connectivity and the Holographic Camera prefab.
Fixing the Spectator View Code
From the two choices at the end of part 4, of course, we go with the adventurous road to fix the code 🙂
Turns out that the AddSurfaceObject() method from the base class SpatialMappingSource was changed. Instead of directly creating a Surface Object from a mesh, this process was now split up into two parts. There is one method to create the surface object, and another one to add it.
Getting Spectator View to run with your own app is obviously the most important step. How to include the required tools – including Sharing – into your app using the latest versions?
More specifically, I’ll add Spectator View to my playground project, which is mainly for placing a hologram in the room (with a few other useful scripts). Currently, this hologram is a nice, life-size skeleton from the Unity asset store.
HoloToolkit-Unity & Holographic Academy
The Holographic Academy course 240 explains how to set up your project to include Shared Holograms. It’s a good idea to work through the tutorial, as it will show you some of the basics of what is needed for Spectator View.
However, as with most of the Academy tutorials, it’s quite old. The HoloToolkit has evolved since then, and the demos often have little resemblance to what your project would look like if you start from scratch.
Once this is finished, import your newly made, fresh HoloToolkit-Unity package into your own Unity project. Alternatively, you can of course use one of the pre-packaged HoloToolkit-Unity releases, which is slightly older, but is usually a good compromise.
According to ABI research, 8.2 million Bluetooth Beacons have been shipped. In 2021, the yearly shipments will have increased to an astonishing number of 565 million beacons per year.
The Bluetooth Beacon Interactor for Windows 10 is a free & open source app for scanning your environment for Beacons. It was the first Bluetooth Beacon scanner app available for Windows 10 and works on PCs, smartphones and even the Microsoft HoloLens.
New Features in Version 2.0
The app has just received an update to version 2.0, which adds the two most requested features:
URLs in Eddystone URL frames are now clickable. You can directly open the web site linked to by Physical Web beacons.
Thanks to a community contribution by kobush, the app now also supports beacons compatible to Apple iBeacons / Proximity Beacons.
You can download the source code of the Bluetooth Beacon Interactor and its base Universal Beacon Library at GitHub. If you would like to scan your surroundings for Bluetooth Beacons and analyze their contents, you can directly download the app from the Windows 10 App Store.
HoloLens Spectator View allows capturing high quality photos including the mixed reality contents as seen by other HoloLens users. To test the complete system setup, the next step is running the supplied sample app in Unity.
Based on my previous two blog posts, calibration of the HoloLens in relation to the DSLR camera has been successfully completed. If you need to complete these steps, check out Part 1 and Part 2 first.
The following screenshot shows the contents of the CalibrationFiles directory, where the app saved both the screenshots of the Canon EOS camera, as well as from the HoloLens. The txt file in the directory is the data file you actually need for your app.
Especially when working with Bluetooth Beacons like iBeacon or Eddystone, you will often want to use embedded hardware to create a low-cost, always running system. This short guide explains how to read Bluetooth Beacon messages using the Arduino 101 / Genuino 101 board.
The Arduino / Genuino 101 already includes a Bluetooth chipset and is based on the Intel Curie platform. You can use the same Arduino IDE as for all the other variants of the Arduino Board.
The TapToPlace script of the HoloToolkit is a great and simple way to place and anchor holograms in the real world. However, it can be problematic if the hologram is placed out of reach / view from a previous session in another room and you can not tap the hologram to place it closer to you once again.
A good solution is to create another “reset” gesture that triggers object placement even if you don’t directly tap the hologram. An easy way to achieve this is the tap-and-hold gesture, which is one of the standard events the Input Manager of the HoloToolkit can send.
To handle interaction events that don’t target a particular hologram, the current HoloToolkit uses Fallback Input Handlers. However, this functionality isn’t very well documented anywhere. This guide explains how to write a custom fallback input handler.