Question SteamVR controller tracking without VR render

Hello,
I am creating an augmented reality project with 3D tracking. I am using an HTC Vive with latest version of Unity & SteamVR.

My goal is to use one controller to have its position, and render a scene in 2D for an external monitor. So I need to unplug the headset HDMI cable to plug the external monitor. Unfortunately I can't manage to it. When HMD cable is unplugged, the whole scene slows down (<10 fps).

Here is what I tried to get only controllers position without VR render:

• Using the "Camera rig" prefab, disabling "Camera" to use my own separate camera
  
  
• Disassemble prefab and use "Controller (left)" alone
  But in both case it looks like SteamVR initializes, and tries to render the game for the HMD.
  
• Changing SteamVR settings (similar tutorials) to use null driver and disable HMD.
  But as far as I understand, the HMD is used for the controller communication. And I don't really need to get rid of it, just to put it aside and disable SteamVR render.

Is there any way to track a controller position and disable any other VR related code ?
(display, head tracking, ...)

Please do not hesitate if you have any idea on what I can try. I have been trying different things since Monday with no luck and can't find anything similar on the Internet...
Thanks !

 

I'm in your same situation...

really interested in some kind of solution/workaround