How to use camera lookat ray Interact with 3D widgets(UMG)

Hello Friends,
In my vr test project, I make some 3DWidgets in game scene, and I can use mouse or keyboard interact with them. But how can I use camera lookat ray or other custom rays to interact with them? My ray can only check the widgetcomponent, but those buttons in it would not be found at all.
And I find Sprirs’s question here

He wants to create a virtual cursor almost like I want to do.
Do I need some mods on it? How do you treat with your 3d widgets in your vr game? Anything will help,thx!