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Scene on wrong position after device not used for a while

October 18, 2018 - 3:23am #1

Hello,

 

we are currently developing a Hololens Application for a fair using Vuforia marker tracking. When starting the application first time, we detect the marker and everything works fine. The problem is, after a user take off the hololens and lays it down to its desired place on the booth and the next user is taking it on after a while, the position of the scene is completly wrong, like either way too low, 3 meters shifted to the left or flying around somewhere on the booth. We need to manually rescan the marker then every time this happens.

Is there a way to detect a wrongly positioned scene or if a user took on the hololens and then force the user to rescan the marker or avoid this problem at all? We know it might be a problem with the way we lay down the hololenses on the booth since they are haning on a hook next to the target scene (facing towards the floor).

Its very annoying to every time check the position of the scene before handing a hololens to a visitor.

 

P.S. the hololenses are turned on all the time and are always connected to a USB cable for charging.

Scene on wrong position after device not used for a while

October 24, 2018 - 7:55am #3

Hi,

you could try to prevent the Hololens from loosing orientation by placing a more distinguishable texture below the hanging Hololenses. To recognise a user change you could check how long the Hololens is looking downwards by measuring the angle between the forward vector and the normal of your floor plane. In addition, if the marker isn't moving, you could use WorldAnchors after recognising the marker to fixate the scene in place (the extended tracking option could work, too).

Scene on wrong position after device not used for a while

October 18, 2018 - 10:39am #2

Hello,

I'd agree that this is likely due to the HoloLens losing its position relative to the environment since Vuforia uses HL's spacial mapping for most tracking use cases.

Perhaps there is a way to introduce a UX element (such as an HL "pinch") that will restart the Vuforia tracker, thus forcing the user to detect the target? Just a thought as I don't believe there is any way to determine if the tracking pose is "way too off to be right".

Thanks,

Vuforia Engine Support

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