Development and Calibration of an Eye-Tracking Fixation Identification Algorithm for Immersive Virtual Reality

[EN] Fixation identification is an essential task in the extraction of relevant information from gaze patterns; various algorithms are used in the identification process. However, the thresholds used in the algorithms greatly affect their sensitivity. Moreover, the application of these algorithm to eye-tracking technologies integrated into head-mounted displays, where the subject's head position is unrestricted, is still an open issue. Therefore, the adaptation of eye-tracking algorithms and their thresholds to immersive virtual reality frameworks needs to be validated. This study presents the development of a dispersion-threshold identification algorithm applied to data obtained from an eye-tracking system integrated into a head-mounted display. Rules-based criteria are proposed to calibrate the thresholds of the algorithm through different features, such as number of fixations and the percentage of points which belong to a fixation. The results show that distance-dispersion thresholds between 1-1.6 degrees and time windows between0.25-0.4s are the acceptable range parameters, with 1 degrees and0.25s being the optimum. The work presents a calibrated algorithm to be applied in future experiments with eye-tracking integrated into head-mounted displays and guidelines for calibrating fixation identification algorithmsWe thank Pepe Roda Belles for the development of the virtual reality environment and the integration of the HMD with Unity platform. We also thank Masoud Moghaddasi for useful discussions and recommendations.Llanes-Jurado, J.; Marín-Morales, J.; Guixeres Provinciale, J.; Alcañiz Raya, ML. (2020). Development and Calibration of an Eye-Tracking Fixation Identification Algorithm for Immersive Virtual Reality. Sensors. 20(17):1-15. https://doi.org/10.3390/s20174956S1152017Cipresso, P., Giglioli, I. A. C., Raya, M. A., & Riva, G. (2018). 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