Fig 1.
Visualization of gaze data simulation and areas of interest (AOI) definition.
(A) Visualization of the three gamma functions used to generate gaze data with three levels of accuracy (0.5°, 1.0° & 1.5°) and examples of the simulated fixations for the left eye of a facial stimulus as the facial target. Each red dot represents the averaged fixation location of 30 simulated fixations; a total of n = 100 data sets were simulated. (B) Visualization of the three steps of the automatic AOI construction process. 1. Facial landmarks from OpenFace. 2. AOI center points derived from the facial landmarks. 3. Resulting AOIs using the Limited-Radius Voronoi-Tessellation (LRVT) method (example with 2.0° radius). Note OF = OpenFace [19]. The stimulus shown in A and B was created for illustrative purposes only and is not part of the stimulus set used in the study (see Methods section).
Fig 2.
Confusion matrices of the fixation classification performance as a function of gaze data accuracy and AOI size.
The percentages in the diagonal represent correctly classified fixation points, while the percentages outside the diagonal represent misclassified fixation points. The percentages in the last two rows correspond to the number of unclassified fixation points (rest of face & surrounding).
Fig 3.
Effect of gaze data accuracy and AOI size on classification performance of simulated fixations (on eyes, nose & mouth) averaged over all facial AOIs.
(A) Visualization of the AOI sizes 1.0° and 2.0° drawn around the blue center points and the simulated fixation points in red (n = 100, averaged over 30 simulated fixations; accuracy 0.5°). (B) Green indicates correct classification within the corresponding AOI, orange and gray indicate misclassifications as fixations within the other AOIs, or no AOI at all. Effect of gaze data accuracy and AOI size on classification performance of simulated fixations (on the forehead). (C) Visualization of AOIs with 1.0° and 2.0° radius and the simulated fixation points on the forehead in red (n = 100, averaged over 30 simulated fixations; accuracy 0.5°). (D) Green indicates the correct classification outside any AOI, orange and gray indicate misclassifications as fixations within the AOIs of the eye region or within the other AOIs. The stimulus shown in A and C was created for illustrative purposes only and is not part of the stimulus set used in the study (see Methods section).
Fig 4.
Effect of gaze data accuracy on classification performance of simulated fixations (on eyes, nose & mouth) within the face ellipse.
(A) Visualization of the face ellipse and the simulated fixation points with an accuracy of 1.5° (n = 100, averaged over 30 simulated fixations) in red. (B) Green indicates correct classification within the face ellipse compared to orange for misclassification outside the face ellipse. The stimulus shown in A was created for illustrative purposes only and is not part of the stimulus set used in the study (see Methods section).
Fig 5.
Effect of viewing distance on stimulus size and fixation point deviation.
(A) Visualization of the stimulus size over three viewing distances (90cm, 130cm & 170cm) with AOIs covering the same facial areas (radius 4.6cm; in visual degree angle: 1.6°, 2.0° & 2.9°) and simulated fixation points on the left eye. (B) Visualization of the interaction between visual angle and viewing distance on fixation point deviation. In both figures (A & B) each red dot represents the averaged fixation location of 30 simulated fixations with an accuracy of 1.5°; a total of n = 100 data set were simulated. The stimulus shown in A and B was created for illustrative purposes only and is not part of the stimulus set used in the study (see Methods section).