[Solved] Absloute Eye coordinates

[Enrico Zschau]

Hi, I want to fetch absolute eye coordinates from a 4C device.

Already tried the stream SDK for C++, but only got relative coordinates within a not exactly defined virtual headbox. Is there a calculation rule, how to convert this to absolute coordinates – within the SDK I did not find appropriate functionality?

Z-coordinate seems also to be quite slow re reaction time – there seems to be a kind of smoothing running over? Some question about this – is this a true Z-coordinate and will it be always the same over different users esp. with different eye-distance?

Thanks in advance – Enrico

[Grant [Tobii]]

Hi @enrico,

If you check out within the Tobii Core SDK Interaction API, you will see the we provide the eye position data is both normalised format (as in Stream API) but only in absolute coordinates with the origin relative to the screen being tracked.

You can check out this data stream within the “Interaction_Streams_103” sample application which can be downloaded on the Core SDK sample page @ https://github.com/Tobii/CoreSDK

The data (including Z acis) is lightly filtered for stability, however reaction time should not be overly slow.. can you replicate the slowness on other users?

[Enrico Zschau]

Grant, thank you for the info.

The Interaction API indeed provides mm coordinates, but they seem to be not very precise (differences in cm range) – monitor was calibrated as suggested by the setup.

Is there an option to get more exact coordinates relative to the eye-tracking device?

Re Z-coordinate slowness: In contrast to the C++ API here in the Interaction API, the Z-coordinate is quite speedy – possibly there is something wrong/different in the C++ API?

Will the Interaction API be available for C++? When?

Are the Tobii pro devices more precisely? I already wrote a request to [email protected], but did not get an answer until today.

Thank you in advance.

[Grant [Tobii]]

Hi @enrico, many of the Tobii Pro range of eye trackers offer higher rates of frequency of eye tracking, customer calibration planes and access to raw unfiltered data so if premium accuracy is required then I would indeed recommend you considering these devices for your needs.

Please also bear in the mind that if you intend to use the eye coordinates for long term storage via the Interaction API then you will still need to acquire a special licence to do so as storage of gaze data is prohibited by the Core SDK Licence agreement.

In reference to the Z-coordinate issue, I have not been able to verify, but have passed on your comments to the developers and perhaps they will come back with some useful feedback for you.

Certainly, there is no option within the Core SDK for ‘extra accuracy’ but it may be worth looking at the different levels of filtering that can be applied to supplied gaze data which could affect the results you are trying to achieve. May I ask if you also got an answer from Sales yet as well and so got all the answers you need? Thanks.

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