Dwarf Fortress Legendary Dining Hall
What are the minimum requirements for different levels of dining rooms or bedrooms? How can you make a room to specific quality level?
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General things that make a room better are the size of the room, smoothness/engravedness of the walls and floor and the quality of the objects in the room.
I know that a 3x3 bedroom with nothing but a bed in will be a meagre bedroom, even if the walls are smooth.
The quality depends on so many factors, I wouldn't be surprised if there did not exist a hard and fast rule for getting rooms of a specific quality...