Caulking (video games)
Caulking is a process used in video game level creation or editing (or mapping) for the generation of a level, or map, that when compiled is less demanding for the computer's graphics card to render in-game than it would be otherwise. A surface that is marked with caulk is not drawn in-game, and is commonly shown as bright pink within the map editor.
Inevitably, certain sides of some objects (e.g. walls) in a game scene will never be visible to the player during normal play. The person making the map can apply the caulk texture, instead of a normal texture, to these surfaces when building the map. The surfaces become invisible in-game[1] and if compiled into a Binary Space Partitioning-File (or BSP-Level) they will also not be added to the list of Leaves (or convex polygons). The resulting reduction of polygons and textures used in the video game level reduces the required video card resources, possibly making the map smoother to play. In the case that a surface which was not meant to be visible inadvertently becomes visible, possibly due to a mapping error, some game engines support drawing caulked surfaces using flat shading.
The conscientious mapper will caulk every side of every building block (or brush) in a map that will never be seen by the player. This is easily done by caulking all sides of a new brush by default, and then by only applying normal textures to those sides that will be seen in the game.