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.
Copy and scale the block around, or keep creating new Walkable Seeds until all the NPC walkable area is filled.
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 [].