A brush is a single piece of level geometry within a map
. Brushes make up the structure of a map, and are used to describe the areas of a map in which the player will inhabit. A each face of a brush is covered with a texture
that define how it will appear to a player.
Brushes, either by themselves or in a group with other brushes, can be tied to an entity
to create brush entities
Brushes can be countless different shapes or sizes, with some rules they must follow:
- Every face of a brush must be perfectly flat.
- A brush must not be concave in any way.
- A brush cannot have any co-planar faces. (That is, faces that lie on the same plane as another face.)
- A brush cannot have any inwardly-facing faces.
Generally speaking, these rules are unlikely to be broken unless more advanced mapping techniques are being used without proper knowledge of how to use them.