I've got a dungeon built. Just navemeshed it (not my first navemeshing) and I was getting a draugr to chase me around to check all of the navemesh, and For some reason, when I cross a piece of a bridge on my map, the draugr will not follow, and will instead turn around and run back.

Here's a pic of the navemesh section.

https://drive.google.com/file/d/0B4BQnEaFh_gvZTRuQl9lNEx3cms/view?usp=sharing

Draugr would be on the left side, while I was running toward the right, then the draugr would stop, turn around and run back up the left side. I cannot figure out why.

As a side note, it is possible to get to the right side by going around the bridge, so I am not sure if the draugr is trying to go all the way around, or if he is trying to get out of line of sight.

ideas?

(just thought of this. I'm gonna try to deleting the navemesh on the bridge and redoing it to see if it works. Will try it when I get back from work. I would love some alternative ideas though. )

Have you tried a pathing test? I cannot see any obvious flaws in your mesh, perhaps it's because you haven't generated any cover yet (might be messing with combat AI)?

Please can you give us a top view of the navmesh?

Some of your triangles look very large, IIRC someone mentioned that they should be about the size of an NPC something to do with the game checking for the centre points of each triangle in order to work out the path.

Also worth just checking your collision, no harm in toggling it on and off (F4) in CK to make sure.

the navmesh at that bridge's entrance (at the very right of the pic) is too narrow from what it looks like to me

(as a rule of thumb, you can think of a navmesh triangle as a hole. if an actor's too fat to drop through it, the triangle's too small for him to path over it)

make a pathing test like antares suggested, selecting a draugr as actor, i think you'll get yellow lines in just that spot

Not sure how to do a pathing test, but I will google it and give it a shot.
The npc stops followin before getting to the doorway. The spot it somewhere under the bridge above, but I'm not certain where.
I'll try a few things when I get home and post a top-down view if none of them work.
Thanks for the suggestions!

Pathing Test http://www.creationkit.com/Pathing_Tests

Thank you all! I have started doing some pathing tests and finding a bunch of issues with my navemesh setup. Most of them seem to be solved by deleteing and replacing navemesh. It's been kind of hairy since I've been using drop down edges with my bridges. I'm a little terrified about what's gonna happend when I fix it and hit finalize.

The dropdown edges seem to be wrecking my path tests. not sure why.

Edit: my pathtests will sometimes accept some drop down edges but not others. Furthermore, it sometimes will accept a path from point A to point B (that goes through a drop down) and from point B to point C (That goes through a different drop down) but not from point A to point C.

Edit 2: I've been trying to let the CK create tris between edges, as suggested on the path tests page linked earlier, but it doesn't always work.

A few notes: Do not fear finalize. It just runs some calculations and does some markup, it isn't actually "Final" or anything. (You can Finalize as many times as you like, and edit the navmesh afterwards) Just make sure it's always the last thing you do after you make changes to your navmesh.

A note on dropdowns, NPCs can only go down them. Just in case that wasn't obvious by their name. They are one way paths, make sure you account for this. (give them a way back up, etc.)

You may have overlapping edges or tris. Have you tried checking your navmesh for errors? This can reveal many issues. Select a tri, hit the triange button with a ? over it, then hit "check for errors" and if it finds any say NO to not delete them, then hit Next Error and it will take you to the broken tri and you can fix it up.

For dropdowns I have used them before and didn't have issues, but now I'm getting some. Not sure if it's an issue with the ck or just my navemesh setup. I have a lot of dropdowns, and I think it could be causing a lot of these issues.

I used the find triangle thing you mentioned and checked the navmesh on one of the central tris, and it said "no warnings", strangely enough. Does it just check around the tri you select or does it flood and check all the tris in the mesh?

I'm gonna try removing some unnecessary dropdown edges and see if that clears up all the issues.

Edit: Removing the dropdowns didn't fix it for some reason.

You have probably seen this but
http://www.creationkit.com/Category:Navmesh

Yeah, I have been remarking them when it does. Recently, I got frustrated and hit "balance for optimization". It cut the crap out of my navmesh, but after I repaired all of the holes, the navmesh works, mostly. Still have a few cases where it won't make paths, and if I can get it to work, I plan to re-add some drop downs I took out to see if they work.

"Check for errors" checks all tris in that contiguous mesh. That said, if you have an overlapping but disconnected edge on 2 tris (on a thin path), it could split it into 2 meshes and won't check them all. You can also see a lot of errors when you say, located in Steam\steamapps\common\skyrim\editorwarnings.txt. That file fills up with warnings. The game tends to find a lot of navmesh issues at that time. Note it clears that log when you open the CK, so copy any relevant ones to a safe location until you can resolve them.

"PATHFINDING: Navmesh 0100625f Cell 'AQarena' (01000D62), Triangle 769 and 770 have opposite normals but are linked

Is AQarena your cell?

Yes, flipped normals are bad, it means the tri is facing the ground instead of away from it. This kind of issue is detected by 'check for errors' so that means you just didn't have the section of navmesh containing the error selected.

Separate navmeshes show up in the cell view object list. Make sure the expect amount is present. (Ideally only 1) Also, you can 'find triangle' based on navmesh FormID and tri number, so you could type those in and it can point you right to the error'd tri, which you can manually delete and replace.

Flippin normals!

ah! AQ arena is an old cell. The one I am currently working on is called AQLabyrinth. I think I have all the navmesh issues fixed. In my next design, I think I may try to make less dropdown edges.

I have started testing the dungeon, and enemies can find me from across the map now, though they some times get congested when a bunch of them are trying to enter a small hallway at the same time. I am looking at doing some flow control and making sure the issue at this point is just congestion and not pathing. Can't wait to move on to clutter and hopefully stop thinking about scatological puns.

Thanks for all your help, everybody! If I run into more issues with the navmesh in the cell I may comment again, but we'll see. ^^