VR headset increases network latency???

Sven and me have discovered a strange problem. As long as the VR headset is not activated and we run the simulation with a normal LCD screen everything works perfectly. We have a 6DOF rig with industrial servos and a custom motion controller connected over ethernet and UDP. Motion is smooth and without any interruptions or jerks.

However, as soon as we activate the VR the data flow to the motion controller becomes unreliable. When XPlane loads the controller goes completely offline and moves to the parking position. I have programmed it intentionally to do that in the case the communication is cut for longer than 20ms (with 2ms output data update interval in FlyPT Mover). That could somehow be explained by excessive network load due to large download traffic over the internet. But this still happens diring the flight. The communication times out multiple times per second and the controller frequently changes between online and offline mode causing the rig to move forth and back from/to the parking position.

I've plotted the time between consecutive UDP packets received and it shows number around 10 to over 20ms. I first thought the VR software slows down the PC too much. But in the FlyPT Mover window the cycle time of the UI and the motion thread is printed in small digits in the corner. The UI cycle time is around 20ms and the first digit of the motion update rate is dithering between a "1" and a "2" so it never goes higher than 3ms.

* VR headset: oculus 3 connected with USB
* PC: Ryzen 7 CPU, 32GB DDR5 RAM
* GFX: NVidia RTX3090
* NIC: 2.5Gb/s, internet and motion controller connected with a NetGear 1Gb/s switch

I'm really clueless why the VR slows down the network communication while evrything else seems to work flawlessly. The graphics renders fluently and without glitches. The PC is not "state of the art" but should be powerful enough for the job.

When I increase the timeout of the motion controller to 50ms everything works but due to the large jitter in motion data timing faster movements feel jerky, now. Could have been a bug in my motion controller software but since it works perfecly smooth without VR I think I can rule that out.

Has ynabody experienced something similar or has an idea what to look for?

Do you checked the load of your CPU and GPU? Because it sounds like your CPU and RAM is to slow.

Which Motherboard and CPU do you have and which RAM? Settings in BIOS and Windows are right? Are you using an USB-Hub?


You could try to lower the resolution of your VR. Even with the best CPU and GPU at the moment, VR is and remains problematic. And when i remind it right, almost every Flightsim is CPU heavy.

I have to install WireShark and a second screen. Debugging like this always requires two persons, the pilot and the "flight engineer".

There is a USB hub but only for the slower devices like joysticks and other control devices. The VR headset is connected directly to the root hub in the PC.

My son mentioned something like modern USB (3.1 or 3.2?) can tunnel HDMI and network data. The VR surely needs a lot of bandwidth so if the USB connection is saturated it might have an impact on network traffic. I thought this were different devices with seperate drivers but I don't know exactly how this works.

I'll try to decrease resolutions and/or FPS and check if that helps.

USB should be fine. Would it be like an restriction at USB Ports, datatransfer or psu wise, it would result in overall disconnects. You can try an powered usb hub, but i don´t think it will improve anything.

It sounds clearly like an cpu/gpu bottleneck, precisely because it works with a normal screen, which has a much smaller resolution.