Disclaimer, this is a working article/best practices guide, it will get updated from time to time based on other Modder's feedback and my own experiences.
Preface/My story ...part of the excitement of modding is to make what was an already incredible game experience and make it new in a way. In my case I was delighted to discover that Clean My Settlement gave me new levels of cleaner settlements allowing for very different experience building settlements. Than I got to try SS1, and later SS2, both making ostensibly a new game out of FO4. I wanted that experience to have even cleaner settlements and tried Scrap Everything and Scrap that commonwealth, ONCE, and it was entertaining but ultimately very unstable experience. So if I wanted to get the level of cleaner, updated settlements I realized I would have to do it myself...because...
Precombines and Previs are a PAIN.
... and because to make most modifications to settlements AND have them be visually stable, you need PnP updated!
So now, having completed all the vanilla settlements, I thought I would share what the process involved and what worked, worked well and what flat out failed like a boss.
Step one, the tools:
"We have the tools, and we have the talent!" Winston Zedmore, Ghostbusters
1. Bethesda's Creation Kit:
To rebuild Precombines and Previs, you need the Creation Kit, as the time of writing this article that is done via a Steam download. Previously Beth had a client you could use.
3. FO4Edit or xEdit:
Available from here, Nexusmods.com. This tool is used to check resources in the mods, for Precombines and Previs it is sort of necessary, later in the guide it is more clear how this tool is used.
3. F4 Creation Kit Fixes - optional - for just learning, if you are planning on making patches, this is no longer optional, as it fixes a major bug in CK.
4. Archive2.exe:
Thankfully, this tool is usually located under your Fallout4 directory, unironically under the \Tools folder. It is very similar to Winzip or my preferred 7Zip. The tool allows you to peruse the contents of the BA2 files, which contain various resources but most importantly for this guide, PnP files!
5. Optional - 7Zip - seriously, it does compression 2-3x better than zip by default and that is going to matter when you get stupidly large files with all the precombines. WinRAR is good stuff too.
Step Two, Basics of rebuilding:
"Only a poor craftsman blames their tools, except in the case of the Creation Kit" Me, now.
So for this guide lets start with a dated but generally accurate video:
Once you have gotten thru that video or if you are already familiar with the basics start again back here....
So lets break down what we saw there.
- Opening up Creation Kit
- Loading up the location/cells of the area you want to rebuild PnP for.
- Hitting the B button to view the cell areas
- Rebuilding the Precombine
- Rebuilding the Previs
- Creating the archive
- Profit!
Alrighty, what our man the mighty Trosski did was mostly correct.
I will go over what he did right and wrong by current modding standards and try to fill in the gaps and make the experience more smooth, because slow is smooth and smooth is fast.
PnP rebuilds and testing are painfully slow if done correctly and just PAINFUL if done poorly.
Step 3 - Opening the Kit - Saving the mod:
Pretty straightforward, in Steam or via direct shortcut activate the application. Initially it will ask you to unpack the scripts, for sanity and simplicity sake click yes and just let it install all the things.
...
Ok, so now that the install is actually done, we can create our plugin!
NOPE, next you have to select the Folder Icon or File->Data
This brings up a window where you select what ESMs, original game resource plugins, you are going to need.Â
By default you will need Fallout4.esm. The others main ESMs are the 6 DLCs appropriately all starting with DLC in their filename.
So for purposes of this guide, select just Fallout4.esm, you can actually load more plugins later if you need them.
It can take a some time to actually load the ESM(s) and other plugins ... once the ESMs have loaded...
NOW YOU CAN SAVE THE MOD!Â
- Click the Disk icon or select File->Save
- Put in your mod name, click save
- By default this saves to the Fallout4\Data folder so you can actually play test it later
- By default you want to start with just an ESP format, so don't worry about that now.
Step 4 - Using Cell View and Render Window
Once you have loaded up Fallout4.esm, the two sub-windows that are of concern for the moment are Cell View and Render Window.
- Lets start with the Cell View, next to World Space, select the drop down and select Commonwealth
- Give it a second to load up all the base game cells.
Now I could try to tailor this lesson to you using ANYÂ settlement to learn this process ... but that would be painful for both of us.
For learning purposes, lets use Sunshine Tidings, its a very forgiving location PnP wise and just very far from any major POIs.
 ...but Abernathy farm is right there! Why not use that? Nope, it has a complex layout, an issue that will be covered later...
   Also Sunshine Tidings has a great hidden pun, its gots lots of Ghouls and its Hex code is 0000DEED!
In the Section of the Cell View, lower down under EditorID click on any cell.Â
Once selected, type in "sun" quickly. It will move the selection to SunshineTidingsExt OR scroll down carefully until you find it.
Right click it and select view, or double click it.
Now Render window will get loading, this could take a while depending on your systemÂ
...
Okay, so you can see in render you are now at SSTC. Play with the interface using the below buttons:
- Hold shift to pan around
- Wheel mouse to zoom in and out
- Hold Wheel mouse button (also called mouse button 3) to move laterally or left to right style.
- Click on an object to make the Shift hold pan work better.
Step 5 - Building the precombines
As seen in Trosski's video, the activation options to create the precombines are:
- World -> PreCombine Geometry for Current CellÂ
- World -> PreCombine Geometry for Loaded Area
- World ->Â PreCombine Geometry for World
- World ->Â PreCombine Geometry for Interior Areas
The only option there that is SAFE and Correct is the first one:
- World -> PreCombine Geometry for Current CellÂ
Suffice to say, the others create more problems than they are worth dealing with. I could explain why to never do them here, but we are still in the BASIC section of the guide...
So lets get SSTC Precombines rebuilt!
Wait! Stop! You can't ... because precombines have a tangled relationship with Previs.
Before you can rebuild the Precombine(s) you need to know what previs is controlling the cells you are rebuilding.Â
Rebuilding Precombines on cells, that you do not rebuild previs on ... breaks previs and possible collisions!
Also, of critical importance, modifying anything in a cell and saving the game changes it last modified property and if that cell doesn't get its Precombine and previs rebuilt, you guessed it ... breaks previs and possible collisions!
If you accidentally  change something you didn't intend, CTRL-Z is not your friend. Just simply reload the plugin by clicking the disk icon, and selecting your mod, and selecting active plugin.
It sucks but I warned you at the beginning about how awful CK can be...
Okay enough stressing you out, I mapped out SSTC in advance for this lesson:
EditorIdFormIDCoordsCornerDescription
Wilderns0000DECD-22,10NWN edge or N most Cabin
SunshT2 0000DEEE-22,9 WWestern side of centeral warehouse
POIJS0100000FF0F-22,8 SWSW most cabin, normally busted, silo/pipes
Wilderns0000DECC-21,10Nedge of large warehouse
SunshT1 0000DEED-21,9 CPrevis, E side of warehouse, large warehouse N edge.
Wilderns0000DFOE-21,8 SSE most Cabin
Wilderns0000DECB-20,10  NEWoods
Wilderns0000DEEC-20,9 E Woods
Wilderns0000DFOD-20,8 SEWoods
In Cell view you can make sure that you are centered in each of these cells by looking at the ground with "B" toggled to show border, shows a bright yellow and black edge to the cell and a blue/cyan crossing in the middle of the cell. You might have to move the mouse around for the blue lines to actually show.
Just to prove you are doing something select some structural object and right click, select edit.
In the bottom left corner select disable on load up. You can use these objects as a reference your mod actually did something...or not.
Alternatively you can move some object around but...
NEVER DELETE A VANILLA GAME ASSET! If you must, move it or disable it, or both!
If you accidentally changed something outside those 9 cells...reload the plugin...I know it sucks.
Finally, once you have your test changes and are comfortable that you are in the correct cell select:
World -> PreCombine Geometry for Current Cell,
There is a prompt, verify the coords and click ok ..... this goes very fast, you get a popup at completion ... click ok.
Repeat this process until all 9 cells are rebuilt.
Lets make sure it worked, in Windows explorer, lets navigate to ...\Fallout4\Data
   I actually keep a shortcut to it on my desktop. I need more hobbies...
Once in that folder, you will see a folder called Meshes, open that.
Inside Meshes, there is another folder called Fallout4.esm, open that.
This is where your precombines files actually went, open that.
There should be a lot of files in there, and you will notice that the hex code or FormID for each of the 6 cells you rebuilt is used as part of their filename.
You might notice a file called {Cell ID}_{ObjectFormID}_Physics.nif these actual tell the game about collision data for that cell, only one these is generated per cell.
If all 9 FormIDs are not represented in the filenames, you probably got a glitch.
This actually happens all the time, go back to the cell that didn't create the files and rebuild it again.
Step 6 - Your first Previs, not the car that's a Prius:
Ok, so you have 9 precombines sets ready to go.
In render make sure you are in any one of those 9 cells. -20, 8 -> -22, 10
Like you saw in Trosski's video you saw there are 4 options under Visibility ->
Visibility->Generate Visibility for Current Cell
Visibility->Generate Visibility for All Loaded Cells
Visibility->Generate Precombined Visibility for Current Cell
Visibility->Generate Precombined For all Loaded Cells
DO NOT USE ALL LOADED CELLS EVER! Please note, in Trosski's video, when he was building Red Rocket's visibility he ran Precombined For all Loaded Cells.
If you do accidentally -> reload plugin...again probably.
Visibility->Generate Visibility for Current Cell, technically doesn't crash CK or the game but by itself it creates visual glitches and adds more processing cpu usage so its a bad idea.
So, back to the 9 cells, once you know you are there, select the only actual viable option:
Visibility->Generate Precombined Visibility for Current Cell
No prompt, no popup when you are done, you just kind of have to wait for the render window to reset.
This can take a while depending, between 30 seconds and 3 minutes.
Once you can move around again in render it is done...
Hey CK Thanks for the notification! /Sarcasm
Alrighty, we could navigate back to the Data folder and investigate \Data\Vis\Fallout4.esm\0000DEED.uvd to make sure its there, but in the last month of building up 27 settlement mods I have never had it fail.Â
Generating Previs only makes once file for every 9 cells, you will not get a previs for every cell you precombine rebuilt.
Step 7 Creating the Archive BA2 Main file
As you may recall from Trosski's video, this step is one of the most straight forward.
Select File -> Create Archive
A new window pops up showing what is going into the archive, you will need to inspect it.
First potential glitch:
If you have F4SE installed the archive process likes to sneak these files into the pack:
Form.pex
ObjectReference.pex
ScriptObject.pexSimply select them from the list and select remove, ctrl or shift multi select works here too.Ok just like when I mentioned inspecting the precombine files in the meshes folder you should do a basic check for all 6 FormIDs being represented again.
You will also see the Vis\Fallout4.esm\0000DEED.uvd file will be there.Â
You can export this list if you want a text file version for easier searching and text manipulation.
Now that we verified the files for archive look good, we can click Pack!
A new file navigation style window shows up. In the file name you want to use the following naming convention:Â
{YourModNameWithoutDotESP} - main.BA2
Your eyes did not deceive you, that is a space, dash, space, the word main than dot BA2.
Type that in there and click save, by default goes into the Data folder, again so you can...
Step 8 -Â Testing your PnP handiwork
So we are ready to see if this puppy works right?Â
Not quite, your mod, like any other must be activated.
In Vortex, with Fallout4 up, select the plugin option on the Left/Bottom area.
Select your plugin and select activate.
Its finally time! Start Fallout4!
Once the game is up, select mods
Than select Y....I mean load order.Â
In load order make sure your mod is both active and at the bottom of the list.
Back out and load up a game.
Once in game, for simplicity sake just hit tilda ~ to open console commands and type in:
coc SunshineTidingsco-opextAlright, explore your handiwork, kill some ghouls and look around.
Congratulations, you just completed the Basic Lesson set on building Precombines and Previs!
Lesson 2 - Expanding on the first lesson, learning how to map previs for yourself and xEDIT!
But why not make lesson 1 longer?
I find its best to just get thru a process and than backfill some knowledge, it builds confidence and you learn more because you have better context.
So you made it thru your first PnP rebuild, now it is time to break down the steps we skipped over in the first part so you can understand the basic anatomy of a precombine/previs set.
Still up for some learning right?
One off the most common tasks for PnP rebuilds are multi-mod patched. Most patches should only rebuild precombines/previs for the exact cells modified by whatever mods are part of the patch. Pretty common sense right?
If one or more of the mods had ANY precombines already done, those also must be re-done! And of course their associated previs files.
Patches require loading up CK withÂ
So the concrete, err, wood example - I was recently asked about integrating a rickety wooden bridge into my Sanctuary mod. To make it work would require loading my DCnR Sanc mod and this bridge mod into CK. From there at a minimum I would have to do all the same precombine cells that were done in the previously. Ok, so for me easy peasy, I just use the same list as before ... and follow the same steps in lesson 1 right?
Thus our Segway to FO4Edit or xEdit!
Bar none, the best tool to see what was changed between multiple mods is xEdit.
This guide is not here to hold your hand for that, instead go with the masters:
First video has the best explanation of how to install the tool it actually does a deep dive on weapon modding you can skip that part if you want.
Second video is more like a clip, its a bit fast (I suggest slowing the speed) but shows a modder opening and expanding a mod in xEdit. The link should jump to around 6 minutes in.
Ok so lets recap what we learned there:
- xEdit installation
- Selecting multiple mods
- Going to the Worldspace cells
- Finding things in the cells
Open up xEdit, RIGHT CLICK and select uncheck all the things, re-check your new mod.
Expand world space, and cells.
Eventually you will see the coords of SSTC:
 -22, 8 -> -20, 10
Take your time to scroll thru the entries and see what records you modified with your first adventure in PnP modding.
As you can see it only shows the records of things you changed, and list sorted by coordinates!
Those coords and FormIds are the main info you need.
The cells that only had an updated previs will clearly show a different timestamp, and the ones with BOTH previs and precombines will show both.
Make sure to go thru the records and visually inspect for those entries.
In this way you can create your PnP rebuild list.
You can go back to lesson 1 and crush another PnP build session!
Cleaning For Fun and Profit!:
Now that you have xEdit/FO4Edit running, its time to do the thing that its famous for, the "Clean". This is actually dont by starting a different exe.
FO4EditQuickAutoClean.exeThis version loads up and asking for just 1 plugin. Select one you want to clean to watch the magic happen.Another use for xEdit it checking for errors, this can be done in normal version and autoclean version. Select the entire plugin, or un-sub-section on the left side and right click, on that list select Check for Errors. After that it will give you a report in the messages tab.
Other mods Custom structures:
The other bread and butter of PnP rebuilds.Â
So armed with the above knowledge what about just building up a PnP for a mod that say adds the a mansion to Croup manor? Maybe its from the nexus, maybe not, doesn't matter.
You know it has no PnP because when you opened the mod zip file...the only thing in there was an ESP!
PnP data is always in the archive BA2 file.
Ok, so same approach as before, open the mansion mod in xEdit and look for worldspace. Expand that until you find a list of all the cells affected by the mod.
Make a list of the FormIDs and coordinates, names of the cell, called EditorID, can help too.
If you are not good with 2/3d drawings, just use excel, calc or G-Sheets and put the formID in a 3x3 pattern in the spreadsheet, or a larger pattern for the larger areas. 6x3, L shape, whatever fits what you are working on.
Last Scenario is the one you already did!
If you are building your own structures you do like we did in SSTC, but follow the 4 rules from above. Its your mods so you should know what cells you worked on. To be fair though I have double checked my own work in xEdit just to make sure...
Test Time!
So the next exercise that you can do to test yourself and do some direct learning is to pick a different than settlement than SSTC and write down each cell that inside the build area.Â
Part - 1 got your settlement? Great! Open CK, and find it!
(Warning, Somerville Place is actually Farm5), the rest of them are mostly what they are in-game.Â
Still a little rusty on how to do this? Hint, this would be Step 4 from above.
Text box inside the Cell View...or carefully scroll down.
Part - 2 Using render viewer, can you see the green/purple boxes that are the border of the buildable area?
Pan around and see if you can track where the buildable area is, while you do that notate the cell coordinates, FormIDs of the cells inside the buildable area.
If you are struggling to see the buildable border lines, an alternative way to select it is...
In the Cell View, on the Right-top side, there is a empty textbox, type in:
buildable
Most settlements use a naming convention like: NordhagenBuildableArea01, SunshineTidingsBuildable etc.
Ok so take your time and get track down those cells!
...
Great you got your buildable info, fill out a text file, hand write it or spreadsheet, doesn't matter:
EditorIdFormIDCoordsMisc notes
XXXXX0000ABCDx,yWestern side of settlementStep 3 map it! Using whatever method you prefer, map the buildable cells out and figure out what previs are needed and the surrounding cells.Â
Remember previs are always divisible by 3 on both x and y
You might need to make your boxes bigger or into a L shape if your settlement crosses into multiple previs.
If you put your settlement info into text or spreadsheet drop a comment of it below to show your handiwork!
Ok so now if you had to, you could open up the settlement you picked, go back to lesson one, but use your cheat sheet and make it happen!
Thus ends lesson 2
Congratulations on your informal orienteering training!
26 comments
This is not a "This sucks and you suck" sort of critique. Just that while I was going down your road, there were too many speed bumps.
Knowing that I shouldn't actually be generating precombines and previs for all loaded cells is the most valuable thing I learned here. I can't believe everybody else has made tutorials that gave us all totally wrong info. Thanks for setting it straight.
So I assumed this had something to do with previs, precombine, and/or LODs, none of which I knew anything about. So here I am in the middle of it. I have a couple questions maybe someone can help me with. Why do we need to run the World precombine geometries on cells we did not change anything in (the geometry is not changed)? Is it just because of the need to have the same date for the previs and precombines?
I followed the video posted here that we are not supposed to follow(doh !) minutes before I found this article, running just the first previs-all step on a few of the cells I modified. But I had already saved those changes into my patch, which also de-junks the island, disables trees, large shrubs, anything that might clip my MegaBlock city settlement. So I don't want to trash all that work needlessly. Is there a way to undo a previs or change it back to default?
The previs operation itself seems ambiguous. I'm still pretty ignorant with this stuff but previs seems to me to be a "source to destination" concept. It's for when you are in a specific cell, looking at another specific cell. I assumed the previs-all function uses the cell you are currently in (like if you right-click and select view on the entry in the cell list) as the "destination" cell and then hits all adjacent cells as the "sources" and calculated THEIR previs to you. Is that how it works? If so, then when doing them one at a time (not the ALL one), what is the source and destination?
From here my calc give that
-5,23 -6,23 -7,23
-5,22 -6,22 -7,22
-5,21 -6,21 -7,21
-5,20 -6,20 -7,20
That all the cells I have to recombine one by one first then previs all of these one by one after.
Creating this grid is easy, no need to search in ck, just enter the numbers from left to right, bottom to top. Or inverse.
The rules is your modified cells must be surrounded by adjacent cells and numbers must follow the same increment, you know
how many and what cells to recombine and previs.
The next quest is test a script to import settlements blueprints in plugin and precombine all.
Thank!
The previs at -6,21 covers the adjacent cells ranging from X coords -5 thru -7, Y coords 20 thru 22
Edit: Ok, I think I understand, we have to visually match the constructible area with the 3x3 cells it's that? No other way to know that directly?
In my case I modified -6,21 + -6,22.
-> 1/ Go to -6,21 : Precombine Geometry for current cell
-> 2/ Go to -6,22 : Precombine Geometry for current cell
When change cell, the ck load all cells rooted to the new position.
-> 3/ Go to -6,21 (or stay in 6,22) : Generate precombined visibility for all loaded cells
-> 4/ Go to -6,22 : Generate precombined visibility for all loaded cells
It's logic after all. And instead of disable/hide map objects I just deleted them.
Precombined archive size 21,9mb
Proof
Edit: I changed more things on tenpines cells and now the precombines are break. I'm searching why. In first instance I think it's possible bug with a tree that has materials problem and bug the precombines. Not sure, but in investigation. As you say, it's a pain lol.
Edit: I think I found why, I analyzed the plugin with xedit and found a change on the branch worldspace/Commonwealth. The bounds of commonwealth has been modified, from 96 to 98 in X axis. I corrected that and recombined and now that work. What I'm not sure about this change on X axis is if it come from me or it's the result a fail during precombine generation... Need more investigation to confirm that.
Edit: I'm pushing investigation, and found a strange thing. Currently after regerating precombines, I have is 2 stairs surrounded by brackets. All object I have removed are correctly updated, but all others added object are not in precombines. I do not understand why it add these two stairs but not the others created houses parts in precombines. I precise these objects are not workshop object, I know workshop objects cannot be added to precombines.
Edit: After searching in various way, static collection, pack-in...Okay, we are in progress. In fact, I have to generate visibility before generate precombined visibility to see others meshes included in precombines. Now what I'm not sure is that must be done for all loaded cells or just the current cell. Have to continue investigation for this point, but we are on the way now. Another interesting point to understand if a static collection is more efficient that a separated statics.
Do the 9 precombines for the 1 previs, than that previs.
If you do not have to rebuild previs for each cell, just the one in the center of the set of 9.
If you do not do a precombine for a previs odds are high some random tree or rock will disappear when standing near it, in that cell.
You can disable objects from precombines by using the "LocationRef" tab, and adding in the NoObject... property, or any kind of link-ref.
Yes I rebuild a custom version of tenpines bluff with precombined + land modification, if I do not use the two visibilities for current cell, the meshes are not in bracket in xedit, that seem the condition to have real precombined meshes (with brackets).
Now the problem I think is the navmeshes. If you want to see? is not totally finished, but is working a123_TenpinesBluff.7z Require Far Harbor because I use one texture from it.
What I retain from this first round, is best to terraforming the land before adding houses... For the navmeshes that seem not very easy to do. It's best to remove all navmeshes first and recreate them with the new land? Add navmeshes after houses creation?
There is a solid video by RealJenn or JennCave, on my article here. There are a lot of links and resources there, but it is not a guide by any means.
Make sure to have backups running and expect CK to crash roughly once per 3-4 hours. Also make sure to set render load cell count from 5 to 1.
Learning PnP is tough with no CK experience, doing Navmesh is another level of challenging, not because the process is that difficult (the video is not that tough to follow) but because it breaks in unusual ways.
This is the mod: https://www.nexusmods.com/fallout4/mods/18995?
But I think since this is the mod which adds Precombines to it that this might be the issue: https://www.nexusmods.com/fallout4/mods/63319
EDIT: Could you comment here if and when you have made it so I can then find it :)?
First thing I am going to try is to bypass the exopatch and see how bad the navmesh and performance is.
If that looks stable than I will release that.
Worst case scenario the exopatch stays and you end up with this load order:
PRP.esp
Starlight_DC...esp
Immersive_Drumlin...esp
Drumlin_Exopatch...esp
Immersive_Drumlin-Starlight_DC--patch.esp
If I can safely bypass you would use the same load order without the exopatch.
Warning though, it fails error check in xEdit. It works fine in game, tested it myself and it loads all the content for both mods.
I messaged two different modders to get suggestions on how to address the issue.
EDIT check here for DL link
If a user did the Trosski / RedRocketTV method with regard to previs, the first generation leaves behind extra XPRI entries once the second completes which increases load times by loading physics stuff that isn't needed for specific references. Thus, only do Precombined Vis after Precombined meshes for optimal results.
Additionally, precombine generation ignores texture swaps. There's an xEdit script that Pra made to mitigate this.
I warn people about not using previs alt as well from above:
... select the only actual viable option:
Visibility->Generate Precombined Visibility for Current Cell
When you say texture swaps, are those the same as material swaps, or custom material swaps?
Reference here for the why. Pra's xEdit script for the issue can be found here.
The semi-automated method is detailed in a manual I wrote that's linked on the PRP mod page.