Half-Life: Alyx Workshop Tools/Level Design/Navigation Mesh
This tutorial will teach you how to create a Navigation Mesh so NPCs can walk around by their own.
Create a test room with a couple walking NPCs of your choice. For this tutorial, I've added two npc_combine_s.
Click on the Navigation button. The Nav Mesh Editing panel should appear on the left side of the screen. Click Create Walkable Seed and drag a block into the first walking area you want to create. It should create a func_nav_markup mesh entity.
To generate the navmesh, the game will flood fill outwards from walkable seeds. You do not need to cover all walkable space in a walkable seed. There may be cases where the flood fill does not reach areas that you wish to be marked walkable. In this case, create more walkable seeds for those areas.
Compile your map. Click the Navigation Button again, and now click Load Nav From VPK. It should now show in the editor the compiled Navigation Mesh. You can hide the func_nav_markup mesh entities to preview it better.
You can download the example map here [].