How to create opacity mask for selected object

[Jil3R]

I have created simple portal system. So the thing is, the portal effect is created using Niagara systems using mesh renderer. once the player entered to the portal, the entered part of the player cannot be seen. the example is like below,

I need to see the other half of the player also through this portal(only for the player) to make it more realistic like the player entered the other world. How can I do that? what technologies that I can use for do this?
is it possible to create a mask and add it to the material of the portal as opacity?

[ClockworkOcean]

Just make the portal material translucent.

[Arkiras]

The way this is typically achieved is by using a cylinder intersection, Unreal has a built in material function for it.

Chris Murphy

[Odd_Panda]

Is there a way to change the shape of the mask, Was looking for a more square shape than circular