Retrofitting Ultimate Trackers with existing Vive Tracker 3.0 implementation (PCVR + Unreal Engine 5.1.1 + SteamVR Plugin + LiveLinkXR plugin)

[VincentCXR]

Hi Vive Developer Community,

I'd like to inquire some assistance with using Vive Ultimate Trackers in Unreal Engine 5.1.1.  

In a project that I'm developing, my team wrote tracker support with Vive Tracker 3.0 functionality in mind with PCVR (Vive Pro 2 HMD).  In that project I was able to spawn an actor and attached it to a specified Vive Tracker, and the transform of the actor (location/rotation) would change accordingly with how I move the Vive Tracker 3.0. 
Additionally I was also able to use pogo pins to do specific actions with that actor (fire projectile for example).

The Ultimate Trackers were promoted in a way that allowed existing Tracker 3.0 implementations to work seamlessly out of the box.  So I hooked up my Vive XR Elite to Vive Streaming Hub, with the Dongle and 5 Ultimate Trackers set up.
The project is reading the trackers, but I'm having an issue where the rotation of the Ultimate Tracker is outputting proper values, but at the same time the Tracker's location values are outputting indeterminate values (nan(ind))

The project I'm working right now only has SteamVR enabled, with the LiveLinkXR plugin active as well.  The LiveLink window is also recognizing the SteamVRTracker IDs (3B-3A*****) properly.  The trackers are also being read using a modified version of the Live Link Data Handler Blueprint from the LiveLinkXR plugin.  

Is there anything that I need to do with the Ultimate Trackers to have them output Location values, and should the Ultimate Trackers be working out of the box with SteamVR?

Software Specs:
SteamVR - v2.2.3
Vive Streaming Hub -  v1.4.8a
XR Elite Firmware - 1.0.999.540

[VincentCXR]

Some snippets of Code I used to output the values, and a runtime example

[VincentCXR]

Never mind, I managed to fix this on my own

[Luca Malisan]

Hi @VincentCXR. I ask you since you seem to have the same setup and maybe you can answer. Now I use Vive Trackers with a Vive Pro 2 HMD for a mocap solution in Unreal Engine. With SteamVR in previous engine versions and with OpenXR since UE 5.2.

I was trying to understand if I can replace Vive Trackers with the new Ultimate Trackers, and so if I can avoid the Base Stations, and have the same mocap solution in every environment. Do you confirm that in UE the Ultimate Trackers work exactly like Vive Trackers? And can I use only the trackers, without having an XR Elite? (I don't need HMD visualisation, I'm only interested in mocap through trackers).

Thanks for the help