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Possible Bug in Unreal SDK for Left/Right Eye Gazes


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Hello VR Developers, 

I am currently working on a VR study with the Eye tracker in the HTC Vive Pro Eye using the SRanipal plugin for Unreal Engine, and I noticed something odd about the eye gazes. Specifically, when plotting debug lines emitting from each eye and out towards their respective eye gazes (one ray for left eye, one ray for right), I found that when I were to cross my eyes the lines would actually diverge instead of converge at a point near the origin (as would be expeted).

Additionally, I did another test consisting of closing one eye (invalid gaze data) and moving the other one, and as it turns out, the *incorrect* eye gaze was moving. So, for example, if I were to close my left eye but move my right eye around, the UE4 project would show the left eye gaze moving around (as it was being tracked by my right eye) and the right eye gaze was invalid (not moving at all). I have reason to believe that this means the function "GetGazeRay(GazeIndex gazeIndexFVector &originFVector &direction);" likely contains a bug that swaps the Left and Right eye gazes (the origins are still correct corresponding to their respective eye). 

To further conclude this point I made a very simple camera pawn from the base UE4 C++ project (as described in the SRanipal documentation) and plotted the debug lines as well. This project has been uploaded to the following github: https://github.com/GustavoSilvera/SRanipalEyeTest with the source and config files (all the other components can be created by following the instructions in SRanipal SDK_v1.3.1.1\SDK\03_Unreal\Document\Eye\Document_Unreal.html) as well as adding my custom C++ pawn (In the github repo) in the scene as it overrides the camera. 

Thanks for taking a look at this!

As a note, I was using the latest SRanipal 1.3.1.1 with the eye tracking version 1 (though the behaviour is the same with version2).

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  • 3 weeks later...

Hi, here's an additional video I took to showcase these events: 

- First I demonstrate crossing my eyes (should cross the lines), then closing my left eye (should only have my right line move), then closing my right (vice versa for left). It is not working as expected. 

 

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