It's fake, but someone or a group of people could make a full 3D game engine.
A full 3D Marathon engine would be interesting.
The way I'm thinking about it is the game engine must be compatible with the original game maps.
5D space can work in full 3D with portal rendering.
Both Unreal engine 4 and Unity engine support portal rendering.
Portal rendering for visibility determination and not the portals that teleport with multiple cameras.
Portal rendering starts with the main camera finding portals with the view frustum in the sector the player is in and the portals have a reduced view frustum to find other portals.
Each sector has a list of portals.
The portals have a (AABB) axis aligned bounding box.
The view frustum is an array of mathematical planes that intersect a axis aligned bounding box or the planes can intersect a line with the frustum planes clipping a portal polygon to activate portal sectors.
The planes normal positive side point inside the view frustum.
Three points make a mathematical plane, two vertices from the portal and the camera and all points are in world space.
The portal vertices go around the front of it in a clockwise order.
If two visible sectors overlap, the portal view frustums can clip the sectors.
Clipping windows can be portals.
I'm searching for more information on portal rendering to improve my Unity Marathon project.