linedefs

Linedefs are a fundamental component of the map format used in the popular first-person shooter game Doom and its derivatives, such as Doom II, Heretic, and Hexen. They are straight lines that define the boundaries of sectors, which are the individual rooms or areas within a level. Linedefs are used to create the layout of a level, including walls, doors, and other structural elements.

Each linedef has two endpoints, which are vertices, and a set of attributes that determine its behavior and appearance. These attributes include flags, which control properties such as whether the linedef is impassable, whether it is a one-way barrier, or whether it triggers a special action when crossed. Linedefs can also have textures applied to them, which are used to create the visual appearance of walls and other surfaces.

Linedefs play a crucial role in the creation of Doom levels, as they are used to define the geometry of the level and to control the behavior of the game world. They are typically created and edited using specialized level editing tools, such as Doom Builder or SLADE, which provide a graphical interface for manipulating linedefs and other map elements.

In addition to their use in Doom and its derivatives, the concept of linedefs has been adopted by other games and engines that use a similar map format, such as ZDoom and GZDoom. These games and engines have expanded upon the original Doom map format, adding new features and capabilities to the linedef system. However, the basic principles of linedefs remain the same, and they continue to be an essential component of the map format used in these games.