I’m doing it similar to David (and probably most of game makers):
- make object Floor1 Floor2 etc roof1, wall1
- give it pivoit in proper place
- make UV, assign texture
All the rest is made in game code. It know that wall is wall (from object name) not roof and it just put it in the game scene.
If you need to tell your game that wall is connected to floor - you have wrong concept to do that or you making lvl builder that need to know which wall is to which room etc. Otherwise I don’t know why game need to know that this edge connect wall and floor. Even blender don’t know that - its just connected. Simple.
My game is Skullstone: Skullstone - a dungeon crawler game