Editing Build (game engine) (section)

=== Room over room ===
One limitation of the Build Engine is that its level geometry is only capable of representing one connection between sectors for any given wall. Due to this, a structure as simple as a shelf with space both above and below it is impossible, though sometimes sprites or voxels can be substituted. Buildings with several floors are technically possible, but it is not possible for such a building to contain an external window directly above or below another window. In addition, some liberties will need to be taken with the staircases, elevators, and other methods of access for each floor.

Several Build Engine games (namely ''Shadow Warrior'', ''Blood'', and ''Redneck Rampage'') worked around this by displaying a "viewport" to another sector through an additional rendering pass. This technique, called ''[[room-over-room]]'' (ROR), appears seamless to the player. In addition to an expanded range of vertical construction, ROR was often used to give bodies of water [[translucent]] surfaces. ROR was never a feature of the Build Engine itself, but rather a "trick" that was created by game developers. A trick used in ''Duke Nukem 3D'' to get around this, as in the case of its opaque underwater sections, was to simply transport the player quickly to another region of the map made to mimic it, similar to the elevators from ''[[Rise of the Triad]]''.

In 2011, a feature was added to EDuke32 called ''true room over room'' (TROR), which allows multiple sectors to be stacked vertically so that each sector's wall has its own connection, enabling vertically-unrestricted structures. The difference between ROR and TROR is that TROR sectors physically overlap in the map data and editor (allowing for easy creation and visualization), rather than being drawn from separate locations using view portals, hence ''true'' room over room. TROR is a feature of the EDuke32 source port, not a game feature or trick.