How to use front-facing camera on HTC VIVE in UE4?

hi, somebody know how to active front-facing camera on HTC vive ,i want capture camera frame to texture with VR, anyone can help me, please!!!

HTC front RGB camera is installed as standard imaging device (just like webcam). You can check it in Device Manager under Imaging Devices tab. In my case it’s name is “MMP SDK”.
UE4 has no buildin support for webcam on windows, so you have to use or create custom plugin for this.
Here is example of webcam plugin implementation for UE4:
https://forums.unrealengine.com/showthread.php?98931-Web-camera-plugin
You probably need to disable use of camera in SteamVR, so device will be not busy and ready to use by your game.