Q: What is a "Brush"?
A: A Brush is basic world geometry. They come in basic shapes and are used to both "seal in" the world from the void (something that must be done to prevent leaks, discussed later) and help define where a player can and cannot go.
Q: What is a "leak"?
A: As you may or may not know, outside the map boundaries is an infinite void where gameplay does not occur and players should not access; the map itself is built inside this void, but is "sealed" by brushes to make sure no entities (discussed later) come in contact with the void. Maps are usually sealed by the Skybox toolbrush (also discussed later). A leak is a failure to seal the entities from the void; leaks will result in either the map not running at all, or a
Hall of Mirrors Effect.
Q: What is an "entity"?
A: Entities are gameplay-related objects and are not "world brushes". Entities can be props, player spawns, particle effects, etc. If entities touch the void or are exposed to it due to improper sealing of the map, the map will have a leak.
Q: Toolbrushes, what are they?
A: Toolbrushes are invisible while playing the map ingame, but have very important uses. They can be either invisible walls, be brush entities (entities tied to brushes, such as "triggers" that activate doors). Toolbrushes are NOT world brushes (with the exception of "nodraw" and "invisible") and cannot seal in the world. Brushes with
one of these textures applied will be considered a toolbrush.
Q: What are the map files called?
A: All maps have the .vmf extension.
Q: How do I embed custom content into my map?
A: You can do so with a little program called
PakRat. This allows you to put all the custom content you used in your map into the map's compiled BSP file so that people don't have to download said content separately. I highly suggest that you have a friend double check your BSP prior to releasing your map to make sure you pakratted all your custom content successfully.
Q: Wait a minute! What about all that hilly and mesh-y terrain, like the hills and uneven ground in gravelpit? That surely can't be just brushes!
A: You are correct. Those are
Displacements, which allows you to take certain faces of a brush and edit them in detail, while deleting the rest of the brush faces. Be advised, displacements
DO NOT count as world brushes, and
WILL NOT seal your map in. When it comes to sealing your map, treat a displacement like an entity.
Q: What is an "visleaf"?
A: Although
Valve Dev Wiki can describe it in better detail, a visleaf is basically something used to determine what should be visible to the player, and what is not based on their position. When a map is compiled, your map generates visleafs (called "cutting up") for the space you have sealed; it uses these to try and determine what should be rendered on screen based on which visleaf/visleaves the player is closest to, and the visleaves next to that.