Navigation Meshes (L4D)
Left 4 Dead uses the navigation mesh to spawn infected. The director uses the Navigation Mesh when deciding where to spawn infected as well as other factors such as light intensity and line of site. By altering the mesh, it is possible to change the type of infected spawning (such as hospital patients and so on) and the density of their spawn.
NOTE: This article was written with experimental information and may not be 100% accurate. This article also assumes that you have read and understood the Navigation Meshes article.
Marking is as important in Left 4 Dead than it is in Counterstrike. While in counterstrike it affects how bots behave, in Left 4 Dead it both controls how they behave and how they spawn. By marking an area with certain attributes certain spawning behaviours can be created. Marking is the same as in Counterstrike, except with extra attributes, such as:
- CHECKPOINT, RESCUE_CLOSET
- These are covered in Your First Left 4 Dead Map
- This prevents infected from spawning in this location. Great for the edges of high places (to prevent awkward situations where infected seem to sleep off the edge of things), wide open areas and in general where you don't want infected to spawn.
- This makes more infected spawn, however this causes Special Infected to spawn very crudely. If you want a difficult map then by all means go to town with this marking - just be forewarned about said crude spawning.
- This prevents mobs from spawning in this particular location.
- This is used to indicate a finale area, and controls the spawning of mobs and infected under finale conditions. This is meant to be used liberally over the finale area. Also the use of a FINALE area may help a map to work.
As you can see, some of these are obvious, and will require experimentation to create the right amount of spawn density or to discover their function.
The type of infected spawned depends on place naming. Simple as that. Simply by looking at the place names that appear on the console input of nav_use_place should give you the right idea of which one you want to use for that particular area. For extra detail, go into scripts/population and read it yourselves. Or, if you're too lazy for that, here it is (numbers indicate percentage of group that will spawn that model out of 100 percent, place names are in bold):
// random zombie type spawned at the church after the mini-finale