Basic Navmesh Editing

Introduction

What is a navmesh and why do i need it?

A Navigation Mesh represents the "walk-able areas" of a map. This data is required by Bots [...] allowing them to "know" how to move around in the environment. Navigation Mesh data is stored in a NAV file corresponding to the map file (.bsp) for which it is used. For example, the nav mesh for cstrike\maps\de_dust.bsp is stored in cstrike\maps\de_dust.nav.

Source: https://developer.valvesoftware.com/wiki/Navigation_Meshes

The zombies in the gamemode use the same system, so i recommend reading the linked article carefully.

Navmesh creation

To create a navmesh you can press the generate navmesh button in the settings dropdown of the f1 menu. This will trigger an auto generation. The generation takes some time depending on map size and your pc specs, so be patient even if your GMod is not responding (It's a performance hungry operation). Once the generation is finished the map will be reloaded automatically. You can test if the generation was successful, by entering nav_edit 1 in your console, if you see coloured squares on the ground the generation was successful. Those coloured squares a called Nav areas, and represent a walkable space, that means the zombies can move everywhere those areas are present.

The auto generated navmesh is enough to make the zombies move, but since its auto generated it will have some issues. Read the following sections to learn who to resolve those issues.

Navmesh Editing