Category: Windows

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AR / VR HoloLens Windows

HoloLens: Adding Fallback Input Handlers for Positioning Out-of-Sight Objects

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.

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AR / VR HoloLens Windows

How to set up HoloLens Spectator View, Part 2 – Camera Configuration & Calibration

The next step to getting the HoloLens Spectator View to run is the calibration. This needs to be done once after mounting the HoloLens to the DSLR camera. The output is a calibration info file that lists how the position, field of view and other parameters differ between the HoloLens and the DSLR.

Step 4: Camera Setup

By default, the Canon EOS 5D Mark III outputs some information on top of the live HDMI video, including a big white focus rectangle. That needs to be deactivated in order to get a full-screen, clear image.

Switch the camera to movie mode, and in the camera settings menu, page “SHOOT5: Movie”, set “HDMI output + LCD” to “Mirroring”.

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AR / VR HoloLens Windows

How to set up HoloLens Spectator View, Part 1 – 3D Printing, Tools and SDKs

We’re developing several HoloLens apps at the St. Pölten University of Applied Sciences, for example in the area of Healthcare and Radiology, as well as for Smart Engineering. For better demonstrations, the HoloLens Spectator View is crucial: it allows taking 3rd person photos and videos of people using the HoloLens app. That helps in understanding the overall scene setup and the interactions between users and the otherwise invisible holograms.

Step 1: 3D Printing the HoloLens Mount

Microsoft has released 3D printing files for the HoloLens mount, which allows fastening the HoloLens on a digital camera. They recommend using Aluminium for better stability. However, we do not have such a metal-based 3D printer, and using an external company would cost several hundred Euros. Therefore, we decided to go with the standard plastic 3D printing instead.

One issue with the current design is that it’s a bit too large for most 3D printers – the mount is a little bit larger than A4. Luckily, our old 3D printer was able to produce the correct size (3DTouch by Bits from Bytes).

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AR / VR HoloLens Windows

How to add Negative Shadows to a HoloLens Scene

Shadows are immensly important for the perception of Augmented Reality scenes. If the holographic 3D object that is placed in the real world has a shadow, it fits better to the world, and users have a better understanding of its placement in the world. This is the result of the study I’ve done some time ago, detailled in the blog posts: Part 1, Part 2, Part 3. How to apply this to Microsoft HoloLens? Negative Shadows are the answer.

HoloLens and Holographic Shadows?

For the HoloLens, rendering shadows is special. The HoloLens displays are light-based – as such, they can add light to a real-world scene. However, they cannot reduce light or darken parts of the real world. If you add a traditional dark shadow to a scene, it simply won’t be visible in the HoloLens.

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AR / VR HoloLens Windows

How to create Photos of HoloLens in Use

Screenshots taken with HoloLens are often difficult to comprehend, as they only show the scene as seen by the user, but not the user itself. How is he interacting with the scene, where is he standing in relation to the view?

Therefore, photos of HoloLens apps usually show a 3rd person view. Getting a real live transmission of the 3D objects seen by a HoloLens user works with the new Spectator View by Microsoft. However, setting that up is tricky: you need 2 HoloLenses, some special hardware and in the ideal case a 3D printed mount.

A simpler approach for a still screen is to take a photo with a good quality camera, and then to render the scene with matching perspective.

Unity itself is not directly suited to rendering a scene to an image, and it also lacks some of the advanced tools to align the 3D scene with a photo.

Here, I’ll describe an approach to use 3ds Max to simulate the view of a HoloLens user in 3rd person view. I used this for our PalKranHoloPlan AR8000 project, which we created during the Palfinger Hackathon.

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