Running 1 level, and a portal rising up to show the 2nd level


I’m trying to make a scene where we are in one level and a portal rises out of the ground. Through the portal you can see a different level. As the camera moves around, you would get parallax between the 2 worlds.

I was initially thinking to achieve this through pre-rendering a video of the 2nd level, and then using BumpOffset_Advanced to achieve the parallax. But, I was wondering if there was a way to actually run both levels at once (or maybe the 2nd level is a sub level). We will never pass through the portal, so that’s not an issue if it’s purely a visual trick.

Thank you so much for any help!

Rendering a video is a possibiliy, but if the player moves around it will be apparent that’s all this is.

Another option ( but costly ), is render targets:
Some marketeers seem to have manged to do this in a non costly way ( which I assume isn’t using render targets ):

I think that example only moves between portals on one level, but I’m pretty sure there are example of multi-level portals on the marketplace ( search portals ).