Rendering in transparency similar to a Vtubing app?

So I am a beginner and I’m playing with UI Elements for Streaming. I’m making and testing my UI in an empty level with no lights or meshes.

In “Project Settings” I’ve already changed the “Post Processing” > “Enable Alpha Channel support…” to “Allow through tone mapper” But I don’t know what to do next. The videos I’ve found are either to fast and skipping steps or their English isn’t great.

When I do Game Capture in OBS with transparency enabled. I just want the UI and whatever else I decide to add in show up with an Alpha background. similar to how Stream Avatar and Vtube Studio works.

Anyone’s time would be much appreciated and thank you in advance.

This would probably be really hard to do.
It’s not in the basic tools in unreal.
You would have to rewrite the low level window creation and how it is drawn. The easiest way would be to set a fully illuminated background (green, blue or magenta) and use the streaming software’s background removal tools.

Only thing that might work is ar (Augmented Reality), but it would probably take a video feed as background and not be see through.

You can at least set borderless window to true in project settings, so that only the character and background would be visible.

Not a perfect solution but something to work with.

in the source you can see in WindowsWindow.cpp

void FWindowsWindow::SetOpacity( const float InOpacity )
{
	SetLayeredWindowAttributes( HWnd, 0, (BYTE)FMath::TruncToInt( InOpacity * 255.0f ), LWA_ALPHA );
}

but I’m not sure if it’s called anywhere maybe beyond the splash screen.

Is there a way to capture my screens in Unreal? For example instead of OBS handling the Screen Capture of my drawing tablet when I’m using Clip Studio, I could throw that in Unreal instead and just have OBS Capture the game client?

Never mind I found offworld live. Which adds this implementation.