How to mask and reveal content from separate sublevels?

Hi,

I am trying to create a “window into another world” effect in Unreal.

In this effect, I want to be able to show a second sublevel through an object like a window or a door. Inside the window, we see a different environment with different lighting conditions. For example, day on one side, night on the other. The lighting from the two sublevels should not effect other and the player should be able to move from one level into the other by walking through the frame. Perhaps using two sublevels and then using some sort of masking effect to reveal the second.

How could I achieve this effect? Would this be something I would do in the material editor? Postprocess material? Or some other way? I can imagine myself using the silhouette of an object (like a door) in screen space to mask the second sublevel.

Any thoughts on how to achieve this effect?

probably not going to use a post process for that.
If you search for portal tutorials they’ll show you how to set up camera’s and render targets.
the hands tearing the sky apart is tricky. maybe if you made a cloth sim in blender/maya so you have an animated mesh that starts as a flat plane and then moves to the side. then give the mesh a transparent material and give it some refraction may look alright. or maybe set up two scene captures one for the other side of the portal and one for the side that is being ripped apart. you wouldn’t necessarily need to mask between them if you use two meshes, one just in front of the other.

probably get a bit expensive performance wise so if this is for mobile or vr you may need to do something else

edit: a less expensive option you may be able to use is a cube map and just do a fade out fade in, rather than a seamless walk through.