@Djangi I'm happy to help you out and answer these questions. Let me know if you need any more information or details.
What is the difference between Vive Eye Tracking SDK (SRanipal) and the tobii xr sdk. While tobii published a clear api reference, I can't find something similar about SRanipal - Feel free to download the SRanipal SDK and the api documentation is included with it. The main differences have to do with pricing, access to raw camera images, and licensing terms where the Tobii SDK requires a special license for analytics usages.
Are there events that indicate the start and end of saccadic eye movement or are is the prefabricated code available to measure this? - No, the SRanipal SDK does not provide functions for eye saccades.
How does does the data flow work from the integrated eye tracker into unity, is all raw data available in Unity or do I get data that is filtered for in game performance. Also, is the data directly fed into the unity plugin or does it run through external software like with other professional tobii products. - You will get filtered data in Unity via the SRanipal Runtime software.
If I want to record data from offline analysis, or do I have build some sort of logger or is there a function in the sdk. Also, is the eye tracking data only available in the plugin or can I also access it externally in windows. - There is no function in the SDK but there are samples available on the forums. Please check this link to see an example of recording the data at 120hz. https://forum.vive.com/topic/5897-getting-verbosedata-at-the-fastest-rate-possible/?tab=comments#comment-26428
I've recently read an article on slippage: https://link.springer.com/article/10.3758/s13428-019-01307-0
The Tobii glasses seem to perform better than the competition in this matter, I'm wondering how far this issue is effecting the HTC Vive Pro Eye. - I will review this article, thanks for sharing it. FYI, we have partnered with Tobii for the eye tracking and SDK so should expect similar performance.
This question might seem a bit naive. Is there an active HTC Vive Pro Eye and/or VR Eye tracking community. So far I've only encountered the Pupil labs discord(which is not very active), the tobii xr support forum and this forum. I hope there are more sources out there. - Eye tracking and VR eye tracking are still relatively new technology and niche communities. If you find any more useful communities or resources please feel free to share them here. 😃