Eye data coordinate system

[Michael Wiesing]

Hey,
I’m using an HTC Vive Pro Eye and would like to know, in which coordinate system the eye data is stored and how it relates to the head coordinates. In other words. If I turn my head but my eye fixates the same spot during the head rotation, would the eye coordinate change during the head movement or would they stay the same?

Hope someone could help me with this.

[Grant [Tobii]]

Hi @alphatierchen, thanks for getting in touch.. the head movements are indeed compensated in such a way that the eye gaze reported will remain consistent (Assuming you focus on the same point) regardless of how you move your head.

If you wish to look at exact metrics, it would be beneficial to check out our XR SDK which can provide streaming data on both the gaze data and head tracking metrics which you can read about @ https://vr.tobii.com/sdk/

If you have a more specific query, please don’t hesitate to get in touch again, best wishes.

[Michael Wiesing]

Hey, thanks a lot. Very helpful!

[Grant [Tobii]]

Pleased to be of assistance, do let us know how you get on… best of luck

[Michael Wiesing]

Hey, I have another question. What exactly does the z-value of the gaze direction represent? Is it the distance between eyes and focused object or something else?

[Grant [Tobii]]

Hi @alphatierchen, the gaze ray is a normalized direction vector meaning the vector (x, y, z) allows you to calculate the direction of the gaze
So the Z does not indicate depth or distance between eye, etc.

[Michael Wiesing]

Thanks for your response!
But could you tell me, what the z value actually indicates?

[Grant [Tobii]]

Hi michael, it’s part of a 3-Dimensional vector to indicate a direction in 3D space, it doesn’t specify anything specific. It operates in exactly the same way as x or y vector. Perhaps this link should explain the concept more clearly @ https://www.superprof.co.uk/resources/academic/maths/analytical-geometry/vectors/3d-vectors.html

[Michael Wiesing]

Thanks again for your response. However, I’m still wondering how the gaze origin is determined. Is the eye tracker able to measure the distance to the eyes?

[Grant [Tobii]]

HI Michael, sorry for the delay in reply. The Gaze Origin is extracted via the Tobii Eye Tracker integrated into the Headset and using our hardware is able to extrapolate the gaze direction thus producing the (x,y,z) direction vector that represents this. If you would care to be more specific in your query, I would be happy to provide further information. Best Wishes.

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