Hi @rasa, whilst it is a nice idea, unfortunately the derivate of the raw gaze locations against their respective time points is not a reliable way to calculate saccadic amplitude as this metric relies on the distance travelled between gaze *fixations*.
To determine therefore Saccadic Amplitude within your program you would need to integrate a fixation filter yourself from the literature in the code and thereafter determine the distance travelled between the two fixation points over a time period.
A number of third parties have created Matlab fixation filters which perhaps you can perhaps translate for your purposes in Unity:
https://se.mathworks.com/matlabcentral/fileexchange/56236-djangraw-gazevistoolbox
& one in R:
https://github.com/davebraze/FDBeye/wiki/Researcher-Contributed-Eye-Tracking-Tools
In any event, you need to be aware that any analysis of data undertaken using the EyeX and associated SDK’s (Unity, Core SDK, etc) in expressly prohibited without the purchase of a special licence.
You can read more about this @ https://transparency.tobii.com/
With additional details for developers @ https://developer.tobii.com/license-agreement/