I'm creating a modular kit for a game level. I started out by making a regular wall, and I'm now trying to use it as the basis to create the corners. The wall has a pivot located at one of the bottom vertices that allows for easy grid snapping, as seen below. You can also see the outer corner I've already created.

The outer wall was created by duplicating the 'normal' wall and rotating by 90 degrees, which placed the main middle edge of the wall exactly on top of the duplicate and left a gap in the baseboard and moulding. I followed this technique to bridge the gap in the baseboard/moulding, which gave me an exact 90-degree outer corner.
I now want to create inner corners (concave). I duplicated the base wall again, and used a 90-degree rotation to place them in the correct orientation. Now, the walls intersect as seen below.
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What I want to do is somehow make another perfect 90-degree corner while the mesh still occupies the same 2x2 square footprint exactly, but I can't get anything to work. I've tried two things:
- Pulling the intersecting edges back, joining the meshes, and trying the same bridging technique. The result is a distorted, uneven bridging, despite the meshes being a carbon copy of each other.
- Joining the meshes and using the Intersect (Knife) tool with Self Intersect. For some reason, it produces a triangle in the middle of one wall, and adds vertices in the straight joining edge.
Is there a way I can do this without resorting to manual vertex manipulation?
