Babylon.js: Pointer direction incorrect when using hands in AR

Created on 2 Dec 2019 · 12Comments · Source: BabylonJS/Babylon.js

When using hands as an input device in WebXR (AR), the pointer direction is incorrect.

Current:
The ray is coming from the thumb and pointing up

Expected:
The ray is pointing forwards, in the direction of the pointing finger.

VAXR bug

Source

RaananW

All 12 comments

It _seems_ like babylonjs is using the grip space instead of the target ray space, but looking at the code that doesn't seem to be the case.

Manishearth on 4 Dec 2019

To me it feels more like a missing 90 degrees on the X axis that is due to the way we are dealing with the cylinder/pointer . I am still checking it, but on different AR issues ATM.

RaananW on 4 Dec 2019

Ah, could be.

Manishearth on 5 Dec 2019

Hi guys, was wondering something. When using the hololens emulator, it seems like the rays from the hands are actually not in the direction of the pointing finger:

It seems like it is the same offset as we are getting (pointing a little higher than expected). Have you tried using a real device, or are you only testing on an emulator?

RaananW on 14 Jan 2020

No, we were using a real device.

That said we did have a bug in the grip space which we recently fixed!

Manishearth on 14 Jan 2020

Going to see if we can test it again with the fixes and report back

Manishearth on 14 Jan 2020

👍1

Any update on that? maybe a new version I can test on as well?

RaananW on 22 Jan 2020

Not at the moment, @jdm has my device

Manishearth on 22 Jan 2020

😄1

Nightly versions are published at http://download.servo.org/nightly/uwp/servo-latest.0.0.0_Test.zip, so you could use those to test.

jdm on 23 Jan 2020

thanks @jdm ! will test on the emulator

RaananW on 23 Jan 2020

Yeah, this was our bug, confirmed that the new patch fixed it.

What was happening was that we were lazily setting the grip and target ray spaces on the input source, but babylonjs requests the grip space first and that's what got set, and we had a copy paste error where they both were set to the same field. Three.js didn't have this issue because presumably it accesses the target ray space first, and when testing stuff outside of frameworks I only ever used a single space so I didn't see a space set to the wrong thing

Manishearth on 23 Jan 2020

oh, that's great to hear!

Closing the ticket. Reopen if anything needs a fix on our side

RaananW on 23 Jan 2020

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