Bot Pathing for custom MvM Maps

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L1: Registered
Sep 29, 2012
[Resolved] Bot Pathing for custom MvM Maps


I'm working on a custom MvM map and have been running into issues with custom pathing.

First, I'm running into issues with the bomb spawn point. Upon loading the map I am met with this error message in the console:
"Can't find blue spawn room nav areas. No legal bomb drop areas are marked"
I do, however, have a designated blue respawn zone with spawn points for each type of bot. I also have the bomb spawn area. Instead of using this it simply spawns all the bots on the ground ahead of the cliff I'm trying to have spawned bots run off of.

Next--using the relay system provided in 'mvm_example' where it utilizes "avoid" sections to dictate bot movement--I'm finding that my bots always take the center path. I do not yet have the left and right flank paths defined, but I don't believe that should be causing any navigation issues.

EDIT: I have also resolved this issue by expanding the size of the avoid sections to cover more nodes on each path area.

If anyone has any insight as to how to fix these problems, the help is much appreciated.
Last edited:


Jul 31, 2009
Are you using nav_generate? If so, you need to "mark" the walkable areas on top of the cliff where they spawn using nav_mark_walkable or no nav mesh will generate up there.


Mar 10, 2008
This error will occur if you have not generated a bot navigation mesh. I've run into the same issue. Checked all the spawns and entities serveral times before I found out how to solve it.

After compiling load your map. Then use the command nav_edit 1 in the console (you probably have to enable cheats first with sv_cheats 1). Now you're in the navigation editing mode. You can use nav_mark_walkable now to mark areas where the bots can walk. Use it several times across your map.

When you're done use nav_generate_incremental (just nav_generate should work too) which will generate the navigation mesh. Once that is completed you can check if all areas are accessible for the bots. If they are not use more nav_mark_walkables and repeat nav_generate_incremental. When you're satisfied with the result use nav_analyze and wait for it to finish. You can then use an additional nav_save, turn editing mode off and test your mission.

The navigation file will be saved with the same name as your map in the tf/maps folder. If you update your map delete it and repeat the whole process.