First some background. I am anol. As a programmer by trade I hate any kind of warning message or error code. I'm irked every time I open a mod in the Creation Kit and have to click the warnings that pop up. Not much I can do about those, so I click through, take a deep breath and continue.

I'm trying to navmesh around some wayshrines that I have placed in various locations around Tamriel. I finish my changes and CTRL+F to validate. No warnings found. Good. Finalize my navmesh, still good. Click save and the problems begin, a ton of warnings pop up. No way to figure out where the issues are so I click Yes to All and finish saving. Next time I load I'm getting additional messages: "NavMesh cell should be refinalized, there are navmesh bounds missing",

So where am I going wrong? I have spent the whole afternoon searching the web and it appears that if a navmesh is marked as deleted, this might lead to the issues above. Sure enough, I find that there are entries marked as deleted in my esp file.

I load a backup file prior to my navmesh changes and see if I can create the navmesh without deleting any of the entries for that cell. I delete one triangle. So far so good. Then I plot a vertex and create a new triangle. Immediately, four navmesh entries for the cell become three. As far as I can tell, there is no way to edit the navmesh without inadvertently deleting individual navmesh entries in the cell contents.

So how do I work around this and get working navmesh updates that don't clog up my Creation Kit with warning messages?

did you remember to generate cover?
since it is an encounter cell (an area with possible fighting) cover has to be redone aswell (http://www.creationkit.com/Bethesda_Tutorial_Navmesh and http://www.creationkit.com/Category:Navmesh)

hope it can help

Don't think it's that. The mere act of deleting and adding a triangle to an existing mesh is causing additional navmesh entries in the cell contents when the mod is saved and reloaded. In one case I started off with four separate entries (one large area, and four islands that were connected to adjoining cells). Deleted two triangles in the main area, and added another, and one of the islands disappeared from the list in the cell contents. Saved and reloaded and now there are SIX entries, with the large area and one of the islands apparently duplicated. What gives?

Now in pictures...

Triangle selected - no issue so far:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh01.jpg

Triangle deleted - again, no apparent issues:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh02.jpg

New triangle added - now I'm missing a navmesh entry in the cell list:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh03.jpg

No issues with navmesh validation:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh04.jpg

Finalize and save... Uh-oh:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh05.jpg

Reload the esp file. Now I have deleted navmesh entries:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh06.jpg

Navmesh related messages on reload:

http://i244.photobucket.com/albums/gg11/Stephen_C_2008/Skyrim/Navmesh07.jpg

It is my understanding that when you delete an exterior vanilla nav-mesh, it hoses the navmesh in the cell. Sometimes even duplicating the navmesh. What I have been told is to drop the entire navmesh below ground and disable it.
Then create your new navmesh above ground, makeing sure to link with the navmeshes surrounding your cell.

This was a while ago, and I am not sure if things have changed for this answer...

So basically disable the navmesh and move it underground, the rebuild the entire navmesh for the cell from scratch? Ugh!

Makes sense though. Will give it (and any other suggestions that come in) a try later today after the Cardinals lose to the Vikings...

So I have four navmeshes in the cell I'm editing. I right-clicked on the largest one of these and clicked the initially disabled checkbox. Then I selected all triangles and moved the navmesh in its entirity way below the landscape. I started creating triangles nowhere near to the other three navmeshes in the cell and the triangles are added to one of the three other navmeshes despite not being connected.

Does this need to be added to the CK bug report? I would say this is pretty critical as my modding efforts have ground to a screeching halt due to this.

Another route you could go with this is to press the collision box button while your static is selected. This will generate a collision box around your wayshrine. The number 2 key toggles the sizing tool on and off. When you are done tweaking its size, double click it, navigate to the "primitive" tab and change it into "_NAVCUT". Now actors will walk around your statics without the need of fiddling with the navmesh

- Hypno

I'm not an expert, but I've been fighting navmesh issues with my Helgen Rebuilt mod for months. Here's a few things I've learned or have been told to do or not to do.

1- NEVER delete an island navmesh. Move it underground. Also, NEVER connect an island navmesh to a non-island navmesh. This essentially deletes it because it is no longer an island if it is connected back to a normal navmesh.

2 - Wherever possible, try to just move existing verts around to accommodate what you're trying to accomplish.

3- Others may disagree with this one, but in certain places, I try to use primitives set to L_NAVCUT to cut the existing vanilla navmesh where I place objects in the middle of a navmesh. For example, say I place a tree somewhere that's already navmeshed, I can select the tree, click on the create trigger button and it will draw a primitive around the tree. Make sure it is penetrating the navmesh, and set it to L_NAVCUT, and it will cut out the navmesh where it goes through it.

Lastly, you might not be able to do what you are trying to do without getting warnings - especially the one about "bounds" missing. I have one I cannot clear up, but everything seems to still work correctly.

Thanks for your suggestions. I'll try the L_NAVCUT method once I finish work today. Unfortunately the situation I have doesn't lend itself to moving vertices as I need to create an additional hole in the navmesh.

Hopefully Bethesda will tweak the CK to improve exterior navmesh editing at some point.

Honestly, I was so terrified by the idea of editing an exterior navmesh, I just placed by building on top and ignored the navmesh entirely (except for connecting a triangle to the door into my new building). Fortunately, it's somewhat out of the way, so it shouldn't be too problematic, just a bit of follower oddness.

It looks like adding vertices is a no-no. It is possible to move vertices or even delete and re-add a triangle that gives a warning on the navmesh check.

To me, this is the perfect place to use the trigger primitive set to L_NAVCUT. In fact I did this very thing with an Inn and it works wonderfully. I had to actually draw 2 primitives due to it's shape, but it was quick and easy. You can see from the picture, this structure overlapped into 4 different cell borders and would have been a royal pain to navmesh. This method made it an absolute snap!

http://ypdesign.com/skyrim/Capture2.JPG

What cell are you editing? I'll try to take a look tonight when I get home from work.

Oh hot damn, that looks incredibly useful, so definitely going to be using that! Thanks!

RiverwoodBridge was the one that was giving me an aneurysm. I've since used L_NAVCUT to get around this. My other observations were around "permitted" operations on the navmesh:- as long as I don't go deleting or adding vertices everything appears to work OK. In this last case I was editing some cells around Ivarstead to remove Bethesda's navmesh errors after I had made some changes of my own.