The door has an animation to open / close itself, and when it's attached to a wall, there's one major problem -- when the door swings in, it reveals not the empty space one would expect, but the segment of wall it's layered on top of!
Since all 3 models are part of dynamic mesh structures, I can't "pre-calculate" what the model should look like to account for the empty space of the door -- what if the player puts the door on the next segment of wall instead?
I considered expanding the "door" model to a "door + wall segment" model (replacing that wall segment entirely), but because I already have two separate shapes of wall, it quickly becomes a combinatorics problem -- 2 models for each door, per door shape (not to mention windows, or a 3rd [or fourth!] wall shape!). In short, this doesn't seem like a tenable solution.
What would work most cleanly is if I could remove a "Door-shaped" segment of my Wall segment mesh, leaving a clear hole that the Door model could snugly fit.
In an equation: Final Mesh A = Mesh A Volume - (Mesh A Volume ∪ Mesh B Volume)
Is an operation like that feasible? My gut tells me that polyhedron intersection is hard, and there might be a better way to do this. I'm also equally interested if someone has a better suggestion on how to solve the initial problem of doors intersecting with wall segments.