Is it possible to use a World Anchor as a positional marker

Hen_Solo · July 2017

Hi,
I would like to store the information of the world coordinates (latitude, longitude) of a spot of a given room and be able to retrieve it when the app is run again. Is this possible by using a world anchor.
The ideal situation would be, if i could trigger an action when the spot in the room is recognized by the hololens and use the world coordinates associated with the world anchor.

stepan_stulov · July 2017

Hey, @Hen_Solo

Yes I know, may be I have not formulated my question well. I meant if there is any trigger if the hololens recognizes a spot in the real world where the spatial anchor belongs to

There is a property on the world anchor to continuously check if it's located (polling):
https://docs.unity3d.com/ScriptReference/VR.WSA.WorldAnchor-isLocated.html

And there is also an event on the world anchor be notified of changes (event driven):
https://docs.unity3d.com/ScriptReference/VR.WSA.WorldAnchor.OnTrackingChanged.html

Is this what you're looking for?

DeanWinch · July 2017

From what I understand, a world anchor won't be the actual marker object.
1. Create a game object for your marker.
2. Place it where you want the marker to show up.
3. Attach a world anchor to it.
4. Next time you load the app, load the anchor from WorldAnchorStore and attach it to your marker object. If the world anchor is located (found/recognized in the environment through spatial mapping), it will show up in the same place again.

On the marker object itself, you can attach a script with any information you want, including world coordinates. I don't think the HoloLens has GPS, so you probably have to place the object manually. Maybe look at TapToPlace.cs in the Academy examples.

Note: Emulator and device have different anchor stores. Also, redeploying the app may wipe your anchor store, so you'd have to save the anchor again.

Hen_Solo · July 2017

Thanks for your answer DeanWinch.
Is there any trigger, when a the world anchor is found/recognized in the environment?

james_ashley · July 2017

@Hen_Solo The world anchor / spatial anchor is something you create, save and assign as needed in your app. You wouldn't accidentally find it or recognize it in your environment. This overview might help: https://developer.microsoft.com/en-us/windows/mixed-reality/coordinate_systems

Hen_Solo · July 2017

Yes I know, may be I have not formulated my question well. I meant if there is any trigger if the hololens recognizes a spot in the real world where the spatial anchor belongs to

Peter_NZ · July 2017

@Hen_Solo

The answer is yes. We have done a POC application that does exactly what you are asked. It was a UWF application that you could set anchors against items. Then when you move within 2 meters of those items it would say ("Near Item 1", "Near Item 2" etc).

james_ashley · July 2017

@Hen_Solo You can attach your spatial anchors to other unity game objects. Then put the proximity logic on the game object itself. Meanwhile, the spatial anchor makes sure that the game object with your proximity logic is always placed in the same location.

For your proximity trigger, you would use something like this (I'm doing this from memory so be sure to double check it):

 if( Vector3.Distance( Camera.main.transform.position, targetObject.transform.position) <= minDistance ){
    // triggered code goes here
 }

stepan_stulov · July 2017

Hey, @Hen_Solo

Yes I know, may be I have not formulated my question well. I meant if there is any trigger if the hololens recognizes a spot in the real world where the spatial anchor belongs to

There is a property on the world anchor to continuously check if it's located (polling):
https://docs.unity3d.com/ScriptReference/VR.WSA.WorldAnchor-isLocated.html

And there is also an event on the world anchor be notified of changes (event driven):
https://docs.unity3d.com/ScriptReference/VR.WSA.WorldAnchor.OnTrackingChanged.html

Is this what you're looking for?

Hen_Solo · July 2017

Yes @stepan_stulov , that looks good :-) . Thank you all

Is it possible to use a World Anchor as a positional marker

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