A control sector is a sector that manipulates another sector in the map to change the way the sector behaves. Control sectors do a variety of things. They can create various FOFs, as well as adding an effect to an existing sector. Control sectors are always placed outside of the main map.
Types of control sectors
The most common form of control sector are those that create other sectors, called FOFs. They are used to create blocks of water, ice, floating platforms, etc. These sectors can be any shape or size, as long as at least one side of the control sector has both the desired linedef action, and the tag number of the FOF sector. This linedef is called the control linedef. The floor and ceiling heights determine the position of the FOF created. Also, any sector effects tagged to the control sector will generally be applied to the FOF. However, this is not always the case, so it is always best to look up the sector type in question before applying one of these. For this type of control sector, the linedef tag determines the sector tag number that will use the effect.
The second kind of control sector is one that is applied to the control sector of an FOF. This is achieved by tagging a new control sector to the FOF. This gives the FOF some special attributes, such as linedef type 606, the colormap. For this type of control sectors, the linedef tag determines the sector tag number that will use the effect.
The third kind of control sector is one that is used for linedef executors. They usually include a trigger linedef and one or more executors. The trigger linedef is tagged to a trigger sector, and will trigger all linedefs in the control sector upon activation.
The fourth kind of control sector is, rarely, one using only a sector type. The best example is sector type 176, map-wide gravity. For these particular control sectors, neither a tag nor a control linedef are needed.
Not all linedef actions and sector effects follow the same guidelines, however. Some linedef actions may require that the linedef be a certain length to work properly. For example, in linedef type 60, Crusher, the speed of the crusher is determined by the length of the linedef. The longer the linedef is, the faster the action will perform. Linedef lengths, as well as the position of the linedef, may be used for many other factors in control sectors.
Sector effects can normally be put directly on a sector. In some cases however, the sector will not activate unless used in conjunction with a linedef executor. While these are rare exceptions, they still qualify as control sectors.