I've been trying to develop a portal rendering game engine and I'm mostly interested in making impossible space with it.

I had the idea to put the sectors that make a game map into groups to make sense of the overlapping space.

Thinking about when the game map gets built, the map sectors are merged together into one mesh and is made one sector at a time until it is done.

There are sectors that can be in two or more groups so other groups can be connected.

The sector groups can't connect with sectors of a different group, so impossible space can be made.

When two or more sectors overlap visually, use the stencil buffer or use clipping.

The sector groups can also be used for collision.

When the player enters a sector it changes to that groups collision for the sector the player is in.

Collision overlaps with sectors part of two or more groups.

If a missile enters a sector and explodes, only the sectors part of that group will be affected by the explosion radius.

The map is one mesh, but it is with sectors and portals and for collision the groups are used.

With sector groups, the overlapping spaces won't be a mess.