40d:Tile attributes

Every tile in Dwarf Fortress is described as Outside or Inside, Light or Dark, and Above Ground or Subterranean. These keywords can be observed from the k menu, when the cursor is located over any single tile. Currently, only the three following combinations are possible:

1. Outside, Light, Above Ground
2. Inside, Light, Above Ground
3. Inside, Dark, Subterranean

The entire fortress site starts out as Inside Dark Subterranean. After that, a ray for Outside and a ray for Light Above Ground falls straight down from the highest z-level for every (x,y) position on the local map, changing each tile's modifiers until something that blocks that particular "ray" is encountered. Due to this behavior, any of the previous three tile combinations will never be encountered in the same (x,y) position on a lower z-level than a higher numbered combination.

Outside vs Inside

This attribute determines where dwarves can go when following the "Dwarves can go outdoors / Dwarves stay indoors" order (o - i). Weather only affects tiles which are Outside. Almost any kind of geometry will block the Outside ray including natural and constructed walls, floors, stairs, and fortifications, and open and closed bridges, floor grates, floor bars, and hatches. A tile which is Outside will always be Light Above Ground, but an Inside tile may be either Light Above Ground or Dark Subterranean.

Light Above Ground vs Dark Subterranean

Plants such as grass, trees and shrubs will grow on sand or dirt where it is Light Above Ground. This attribute also helps determine which types of crops can be planted on farm plots that have been constructed on top of the tile in question. Dwarves who spend excessive amounts of time in Dark Subterranean areas may suffer from cave adaptation. Very fews types of geometry block the Light Above Ground ray: only cliffs (natural walls), ground (natural floors), and natural stairs (those carved out of cliffs or ground). Tiles which are Dark Subterranean will always be Inside, however Light Above Ground tiles may be Inside or Outside.

Tips

• Make sure all key fortress areas are Inside. This will allow dwarves to access them when the "Dwarves stay indoors" order is in effect, such as during a siege. To secure an Outside area, enclose it in constructed walls (b - C - w) and put constructed floors (b - C - f) over it on the z-level above.
• To help dwarves avoid cave adaptation, use Light Above Ground in high traffic areas, such as a meeting hall. For fortresses with lots of cross-floor traffic, the central fortress access stairway can serve this purpose, if every floor's natural stairs are removed, a channel is dug, and the stairs are replaced with their constructed counterparts (b - C, then u, d, or x).