ExtractGazeEvents¶
Detect fixations and saccades in continuous gaze data.
Incoming gaze data must have a time axis. Detected events are used to create entries in a new Instance axis. Gaze-event detection parameters are often expected to be in specific units such as degrees of visual angle. Precede this node by the SetGazeMetaData and GazeScreenCoordinateConversion nodes to convert the gaze data to the expected units. Version 0.1.2
Ports/Properties¶
data¶
Data with Pupil Stream(s)
fixation_algorithm¶
none: Do not create fixation events. between saccades: Use the saccade algorithm only, and segments between saccades are assumed fixations. I-VT: Velocity threshold based algorithm described in Salvucci and Goldberg 2000. I-DT: Dispersion threshold algorithm described in Salvucci and Goldberg 2000.
saccade_algorithm¶
none: Do not create saccade events; between fixations: Use the fixation algorithm only, and segments between fixations are assumed saccades; V+A threshold: Velocity and Amplitude threshold, based on Armstrong et al Neuron 50, 791-798, June 1, 2006. Currently works in offline-mode only.
min_fixation_duration¶
Minimum duration (in seconds) of contiguous data meeting other fixation criteria for the segment of data to be considered a fixation.
max_fixation_duration¶
Maximum duration (in seconds) of contiguous data meeting other fixation criteria that can still be considered a single fixation. Note that if this is None and using I-VT then fixations may also include smooth pursuit, or if this is not None and using I-DT then fixations may also include smooth pursuit.
dispersion_threshold¶
The maximum dispersion distance allowed beyond which the most recent data point will be considered part of a new event. Pupil Labs uses 3 degrees. Dispersion threshold doubles as a distance threshold for dejittering when using I-VT.
robust_dispersion_frac¶
The proportion (0,1) of largest dispersions to be included when estimating (median) the dispersion. Set to 0 to use only the single maximum (efficient codepath). If you find that your fixation events are terminating prematurely, then you can increase this number to .1 or .2. Alternatively, you can increase the dispersion threshold.
merge_fixation_distance_threshold¶
Consecutive uninterrupted fixations with fixation points separated by less than this amount will be merged into a single fixation.
velocity_threshold¶
For I-VT only: The maximum velocity allowed beyond which the most recent data point will be considered part of a saccade. Sen and Megaw use 20; Komogortsev recommends (?) 70, 20-50?;
distance_metric¶
https://docs.s cipy.org/doc/scipy/reference/generated/scipy.spatial.distance.cdist.html
dejitter¶
Dejittering is only supported when using velocity thresholding. It doesn't make sense in the context of dispersion thresholding; just use a larger threshold if your data are noisy. The dejittering algorithm is described in a paper titled Improving the Accuracy of Gaze Input for Interaction by Kumar and Klingner. http://graphics.stanford.edu/~klingner/publications/GazeInputAccuracy.pdf
set_breakpoint¶
Set a breakpoint on this node. If this is enabled, your debugger (if one is attached) will trigger a breakpoint.
metadata¶
User-definable meta-data associated with the node. Usually reserved for technical purposes.