It seems like every procedural dungeon generation tutorial focuses on how to avoid overlapping rooms, so how would one go about intentionally overlapping those rooms instead, possibly treating the overlapping areas as either new rooms or connecting passageways?
In trying to imagine how this might be done, I think that there might need to be a property for each room that is similar to how opacity works with digital color mixing, and that it could then operate on what would essentially be a modified flood fill algorithm, but are there other approaches that would be well-suited to this? What other considerations might be necessary?
This post appears to be the closest thing that I can find to an answer to this question, but it seems to be concerned with eliminating corridors rather that allowing for overlap:
