Build (game engine)

The Build Engine is a first-person shooter engine created by Ken Silverman, author of Ken's Labyrinth, for 3D Realms. Like the Doom engine, the Build Engine represents its world on a two-dimensional grid using closed 2D shapes called sectors, and uses simple flat objects called sprites to populate the world geometry with objects. The Build Engine is generally considered to be a 2.5D engine, as the basic world geometry is two-dimensional with an added height component, allowing each sector to have a different ceiling height and floor height. Some floors can be lower and some can be higher; the same is true with ceilings (in relation to each other). Floors and ceilings can hinge along one of the sector's walls, resulting in a slope. With this information, the Build Engine renders the world in a way that looks three-dimensional, unlike modern game engines that create actual 3D environments. Though the Build Engine achieved most of its fame from powering the 1996 first-person shooter Duke Nukem 3D, it was also used for many other games. Sectors are the building blocks of a level's layout, consisting of a two-dimensional polygonal outline when viewed from above, with the top and bottom faces of the sector given separate altitudes to create a three-dimensional space. Hence, all walls are perfectly vertical—anything appearing otherwise is technically a sloped floor or ceiling. The word room can be used as a loose substitute to aid understanding, though one room in the game world can consist of many sectors, and parallaxed skies can give the illusion of being outdoors. Sectors can be manipulated in real-time; all of their attributes such as shape, height, and slope could be modified "on-the-fly" by games, unlike the earlier Doom engine. This allowed games to have destructible environments, such as those seen in Blood. This technique is similar to the use of push walls in the earlier Apogee Software title Rise of the Triad which featured similar dynamic environments.