How do you do navmesh on a whole exterior region?

If you're asking for a new & custom worldSpace you've created, you may have success doing a recast auto-gen (using the default settings). While nothing is selected in the renderWindow, open the navMesh toolbar then open the navMesh pulldown, generation, recast-based. Of course, you'll have to tweak the cell-borders so their vertices line up; and you may have to tweak some tight spots - as I've found auto-gen to leave a bit more extra space non-navMeshed than I think it should (and I'm not willing to mess with those default settings just yet to experiment.. heheh).

If you're asking for a Vanilla cell, my opinion is that you have to edit it by hand. This means adding individual vertices and creating new tri's (cntl-right-click is easiest). Any time I tried to auto-gen a Vanilla cell it ends in disaster. I would also suggest not actually moving or deleting any Vanilla vertices - unless you absolutely HAVE to... the more Vanilla you change the more likely there will be problems. ADDING to it doesn't seem to cause NEARLY the same amount of drama (if any), so I try to make my mods completely by this add-only method. It'll also reduce the possibility of conflict with other mods; though if you add a house to the same spot someone added tree... you'll wind up with indoor nature.

You can do generation on a whole region using the region editor much like you would do an interior. However, I'm sure it will be messy so you must still clean up every single cell by hand. I, for instance, am just slowly doing each cell. As I finish an area, one by one I generate for a cell, give it a quick clean up and finalize it.

Cell by Cell????

Ihave 700 and you should have over 1000 ... how you do cell by cell?

Very slowly.

And most of them are ocean. You don't need to navmesh all that ocean space. Or you can do that with auto generation just so it's there. I've placed border cells around my land so you can't swim off into Oblivion, so that cuts out a lot of cells. As for actual land ones, if I finish an area, I do the affected cells and the cells immediately around there. Since I'll be doing about 40 areas over the next 5 months, I'll slowly do little bunches of 10 or so cells, and when the mod is done, so will all the navmeshing.

IMO the best policy for larger mods is to never put off navmeshing til the last thing. it is always better to navmesh as you build, then go back and update when needed. if you build your entire world first then are left with the hideous task of navmeshing the whole thing, you will probably either get discouraged or end up doing a half-assed recast job on it (unless for some strange reason you REALLy like navmeshing).

i have a relatively small mod compared to some of you guys (less than 100 cells total) and i find it a pain having left even 10 cells un-nav'd. i personally do not allow myself to ever use auto-gen'ing and i do all my navs by hand. but i nav as i build so the work doesn't get monotonous and discouraging, and overall it keeps the modding spirit fresh, and frees up your creativity instead of smashing it to a halt once you realize you have to hunker down and spend an extended amount of time in navmesh prison.

The problem is I use a different approach I guess on Worldbuilding ...

1 I create the whole landscape
2 I cut in major features liek mountains lakes rivers etc
3 I sketch up areas of interests like cities , caves , passages , woods etc ...
4 I start detailing those areas more and more in severall passes of Large items , medium items up to small details ..

I can only generate the navmesh when all is done just because the NPC could walk on items or around them even the small ones otherwise I guess they woudl clip or get blocked ...

I have almoust 700 cells tough of those many are mountains ... or sea ... I have seen tht regions in tamriel are called some just like navmesh , and I see several regions do have more navmesh regions overlapping , what this may mean?

The ocean should at least be navMeshed near the coastline, or enemies won't follow you into the water (nor will your followers). I've never used the Region Editor to do navMesh... I never modded FO3/FNV and I hadn't heard you COULD use the Region Editor... I'll have to keep that in mind when I begin MY big worldSpace mod (9 quads).

As for recast autogen... I've had VERY good success with it, except in environments which overlap vertically. Example: I have an interiorCell that has like 7 distinct areas (large rooms/etc) which circle around each other, some going above or below others. Doing an auto-gen tends to create islands inside statics that I have 'creatively' placed (such as a mountainside mesh used for a ceiling). You really gotta go back through it and check for extras, or for places that didn't get covered. But cells such as that, I generally do by hand as it seems to be easier and quicker than having to search every cranny of the space for uncool tri's.

But for 'open-world' spaces... I swear by recast auto-gen. I always go through and tweak it though; I never just leave it as-is, unless it's in the utmost of simplest places (like a round bedroom in it's own cell). I couldn't imagine having to do 9 quads vertex by vertex... even cell by cell is kinda heinous, so I'm really hopin' that regionEditor works wonders on simple landscapes! (my world isn't as vertical or rocky as Skyrim... it's all rolling hills and forest with lots of water)

I would, personally, follow Prometheus_ts' workflow when it comes to something like this. Mainly because I know too much about the navMesh editor in the CK to trust it in the slightest. I've seen it generate errors for no reason, destroy cell-border merges when using certain methods, and even corrupt the preferred/water/regular flagging. I've seen it crash the CK just by doing a find cover. It is WAY too buggy, in my opinion, to do navMesh early on and then go back and re-finalize after tweaking... way too much could go wrong every single time you use it, so I try to minimize my risk exposure.

I kinda follow that workflow ANYWAY, as it's the logical workflow if doing a project alone (as opposed to having different people doing different regions). I may not do the ENTIRE thing that way, but I'll do a 'rough draft' - and then go back and specialize certain places at different times. But I'd still wait until afterwards to navMesh, simply because I tend to change my mind as to strategic placement of obstacle-statics and the like... so I KNOW the navMesh won't be around for long in many cases.

But those mountains, and most of the ocean probably, doesn't need navMesh if it's too vertical or won't ever be traversed by Player & Co... so that'll save you some time. The Vanilla regions may overlap (I assume you're talking about the regionEditor?) because it may auto-merge cell-borders if they do. I not, one would have to go back and merge the borders by hand. This is only my assumption (and hope.. heheh).

May be there is no need to NAvmesh all the terrain , may be it is sufficent to navmesh it where there are monsters and in places where NPC will move ?

Unless the problem may arise for followers tough ...

Precisely. You only need to navMesh the places you expect Players and monsters to go. If you have a huge landmass, there may be vast areas of forest (for example) in which there are no monsters... but Players may wander in there anyway - hoping that there is. If they have a follower, it won't go in there though; but that's not really a big deal unless Player travels across to another area which IS navMeshed. That would make the follower have to run all the way around to meet back up with you, which may take a while depending how far.

But there are tricks you can use to prevent Players from going places you don't want them to... my method of choice is using collision boxes. They're invisible and have minimal tri-count; and will still work if people disable border regions in their INIs (can you do that in Skyrim? I haven't looked into it yet, but EVERYONE did that for Oblivion). So if you have one long collision box per cell, slightly overlapping each neighboring cell, you can cordon off entire areas and not have to navMesh them (or place fine detail that noone will ever see.. saving THAT time-spent for detailing the high-traffic areas).

Sono familiarità con l'italiano se si preferisce o che sono più a suo agio in tale lingua. Anche se ... Io sono nessuno studioso veneziano, heheheh.

If you look at Tamriel from vanilla Skyrim, half the more remote, cliffy areas don't even have navmesh. As the player, you can go almost anywhere, but a lot of the more obtuse mountain-side stuff has no navmesh. Beth didn't seem to mind, so you should be able to get away with doing the same. (As am I)

Though, I would refrain from blocking the player in. Part of the TES/Bethesda Sandbox feel is being able to go anywhere. I get annoyed when I'm boxed in when it doesn't appear that I should be.

In my mod, the player can go wherever they want within my land. On any mountain, up any cliff. I don't restrain them at all. I simply keep them from swimming off, and there is one quest where I box them into a place. That's it. Keep it open, but don't navmesh the more extreme stuff that players will rarely go on.

I can see the value in allowing Player freedom to roam, but I personally would get VERY disappointed when using Oblivion mods which had vast worldSpaces of nothingness. You keep walking and exploring, hoping to find something of meaning or value - but nothing but flora generated by the regionEditor (most of the time not even done WELL). I can see if the mod's description specifically TELLS you where the true wilderness begins, so one can avoid wasting time searching it, but just having vast nothingness without warning.. I dunno.

The method I actually use for my vast worldSpace is dummy terrain. I would generate all the distant LOD and flora/etc, then delete those cells manually (3rd party software). I haven't tried this for Skyrim yet... but I'm hoping it works. The point is that when Player gets to a spot where nothing begins, the land simply disappears (literally)... can't get much bigger a warning than that! I place that no-land's-land far enough away from the 'beaten track' that only the most adventurously explorative Players would see the land disappear. This technique also saves TONS on load-times and filesize.

[EDIT: perhaps instead of collision boxes blocking Player outright, placing TRIGGER boxes instead may be better. They'd be scripted to give a simple notice that Player is entering the true wilderness... that way people THAT bored can go ahead and still wander the nothingness if they feel so inclined.]