Motion Controller won't track Vive wands

I am having an issue where Unreal Engine isn’t tracking my Vive wands. In trying to find the root of this problem, I set up a quick print statement in the VRPawn blueprint I’m using, which simply consists of a camera root and camera, a left motion controller with a static mesh, and a right motion controller with a static mesh.

This print message is printing whether the motion controllers current have a tracked device using the IsTracked function, and I saw that ‘false’ was being printing constantly after launching the scene in VR Preview with the HMD and wands turned on. I know that the wands themselves are working as I can press the system menu button and pull up the Vive Dashboard and see the wands moving around just fine while in VR Preview. Any idea what could be going wrong?


Windows 10

HTC Vive

Unreal Engine 4.15.1

Discovered the solution to this issue. Turns out the issue was caused by my solution to another issue I thought I had (not-so) cleverly solved. The first issue was that I was getting the strange screen effect where either my Vive HMD was either red-eyed or I was getting the cross-eyed view where there was a black bar of the far left of the left eye and the far right of the right eye, with the VR Preview doing funky stuff in the middle. The solution I had discovered was that if I rebooted by HDM between every VR Preview, it would render normally. Then the issue I had stated in the question started occurring.

After wrecking my brain about it for a few days, I came across a discovery: whenever I first loaded up my project without the controllers turned on, then turned them on, the output log would recognize them and assign them hands. When I went into VR Preview at this point and got to the cross-eyed view, as mentioned above, they were tracking just fine. But when I rebooted the HDM to fix the view, it stopped tracking them. So as far as I’ve discovered, you cannot reboot the headset after the project has launched or the wands stop getting tracked. So then I needed a solution to the red-eyed/cross-eyed view that I was experiencing so I could actually see the game. I found an answer covering this already, linked below. Turns out the issue here is when VR Preview is launched, it’s placing the game screen that’s supposed to be in the main screen of your system into the Vive HMD, which does not appreciate things overlapping its view and causes the error.

The steps to place it back where it’s supposed to be are in the comments to the question:

Thanks, this happened to me, cost me an hour, the “is tracked” showed this was the problem, thanks for replying to your comment.