Bungie was going to rewrite the Marathon engine to be fully 3D, but they quit to make a new game.
http://marathon.bungie.org/story/newmar ... #Marathon3
A full 3D portal rendering engine can be made and if I make it, I want to name it Marathon: Simulacrum.
Simulacrum is A full 3D game engine made to look and act like Marathon.
I've made my own 3d portal rendering to make use of Forge Plus in Unity.
The plan is to have Simulacrum load the Marathon files into Unity and play the trilogy in full 3D.
I can go beyond just loading the files.
New map format.
Portals that are on the floors and ceilings.
Portals that have 20 sides.
Down scale the maps to 128 so bigger maps can be made.
Slopes.
Platforms that move and travel from one sector to another.
3D models and other things I can't think of.
5D space is the first thing that needs to be correct, then work on other things.
I will use Unity so it will be cross platform.