How to get output from the eye-tracker faster than Update in Unity

[Tatiana_K]

Hello!

So in the specs it is said that the eye-tracker data output frequency is 120Hz, however, I can not get it higher than around 90Hz, which is the rate at which my scene is rendered. I tried with FixedUpdate with a small fixed timestamp, but it just repeats the fixation values on the extra cycles.

Could you tell me please if it is possible to obtain the output from the eye-tracker faster than the Updates happen? I apologize for possibly noob questions, but also, if I will make my scene render faster, will it help, considering that the vive itself refresh rate is 90 Hz?

 

[Corvus]

@Tatiana_K Please see this post about getting tracking data at 120hz in Unity:

https://forum.vive.com/forums/topic/5897-getting-verbosedata-at-the-fastest-rate-possible/?do=findComment&comment=26428

 

 

[Tatiana_K]

@Corvus  thank you!
 

[ScottHerz]

It would be nice if HTC cleaned this up. They advertise a 120hz eye tracker and then make you work around their own poorly threaded architecture to get it.

[Daniel_Y]

There is callback mode supported in 120 FPS now after check "Enable Eye Data Callback" as the figure shown below; And, then register a callback function by SRanipal_Eye_v2.WrapperRegisterEyeDataCallback(). Could refer to its usage in sample included in SDK.

 

 

[imarin18]

Dear @Daniel_Y,

 

Thank you very much for sharing the helpful information.

The callback function in version 2 enabled me to sample the eye data at 120Hz. I referred to the script of SRanipal_MirrorCameraSample_Eye_v2.

 

Best regards,

imarin

[Asish]

Hello @imarin18

The callback function in version 2 does not give me the eye data at 120H. Unity stats shows variable FPS like 90 to 140 FPS. How can I get it exactly 120 FPS?

@Daniel_Y

[Corvus]

@Ashish How are you measuring the callback data frequency? If you're using the callback method or a separate thread for 120hz data it will be independent of the Unity FPS.

[Asish]

Hi @Corvus, I'm using callback method. According to @Daniel_Y I enabled v2 and then used sample UI code to show FPS from http://wiki.unity3d.com/index.php?title=FramesPerSecond&_ga=2.258332745.253243703.1593390743-1664584608.1593097261&fbclid=IwAR2zAe7hOiiEzb822jA5lIFOlpDGXqUhf-W2WYlbf00-B4uo-Y1-IhDqYtQ

I get 30 to 45 FPS. I checked my monitor frame rate is 60Hz. Please take a look at screenshot and let me know how can I get 120 FPS. 

 

Thanks in advance!

 

[shomik]

Hi @Daniel_Y and @Corvus

I have several queries and findings :

1. In vive developer page I found that, refresh rate for headset and for eyetracking output frequency are different. For headset it is 90 hz and for eyetracking output frequency its 120 hz.

https://developer.vive.com/resources/knowledgebase/vive-pro-eye-specs-user-guide/

2.  I am getting different refresh rate for headset on different monitor. I tested on two monitors, one is Asus ROG(default monitor fps:144hz), another one is DELL(default monitor fps:60hz). From Asus ROG I have got 90 HZ frame rate for headset but from Dell monitor I am getting less than 60 hz. I wonder what relationship between monitor refresh rate and headset refresh rate is. Can you explain? I have calculated refresh rate using the following code:

https://paste.ubuntu.com/p/YYHqbpnPNC/

3. Can you suggest or give example code how I can measure refresh rate for headset and eye tracking output frequency?

4. The last thing is: “Gaze data output frequency (binocular):120Hz” , to my understanding this means, we can collect 120 data points per second, right ? is there any dependency between Headset refresh rate and eye tracking output frequency?