De-Isolation Tutorial

by dev_akm

UNDER CONSTRUCTION

Introduction

Normally, when people make changes to a plugin, they just open it up in the CS, make their changes and save.

But this isn't always a good idea. Consider these scenarios:

• What if you have one large mod and want to offer several optional tweaks to various aspects of the main mod? Maybe it isn't a problem to have several versions on the first release, but how quickly are you going to get tired of repeating this process each time you update the main mod? Maybe you actually need the optional tweaks to be kept in separate add-on files?

• What if you want to make tweaks to someone else's mod and you want to avoid having your changes wiped out by the next release of that plugin?

• What if you want to use something from one of the official DLC mods? Distributing your altered version of an official plugin isn't a great idea, creating a binary patch (binpatch) for it is very cumbersome and prone to errors, and it's very likely that someone else may have the same idea (rendering your mods mutually exclusive).

Mods based on Oblivion.esm don't have this problem because it's a master file (ESM). Multiple add-on plugins (ESPs) can alter it at the same time without any problems. Unfortunately, TESCS doesn't let you use plugins as masters, even though the game engine actually doesn't mind at all.

Mastering

Many beginning mod creators get frustrated with TESCS because it seems to let you select Oblivion.esm and one or more ESPs in addition to your "active" file. The content from those ESPs will appear to be usable, but it's not. When you save your new plugin, TESCS will refuse to remember that your plugin was built on top of those other ESP files. If you then reload your newly created plugin, TESCS will then be lacking the internal references to connect it back to the ESPs you had loaded before, and you'll likely get lots of error messages and things generally won't work as desired.

This behavior is known as Mod Isolation.

Fortunately, there are several good strategies for how to get around this limitation. All such solutions involve either making your own actual master(s) or tricking the game into thinking you've got your own master(s). The latter technique is known as Mod De-Isolation.

• ESM Mastering. You can make the base (or "source") mod(s) into a master by converting it to an ESM. Both TES4Gecko and Wrye Bash provide functions to let you convert an ESP into an ESM. It works great for lots of things, especially new content that's not directly connected to the Tamriel worldspace.

But masters should not modify other masters -- only plugins should modify masters. When one master directly modifies another master, problems can result, such as vanishing landscape. If you try to use TESCS to make a mod based on a master that modifies another master (especially worldspace changes), such as the official DLC plugins, then you will very likely encounter a bunch of "assertion errors" when you try to save your changes, leaving you with a plugin containing corrupt cell records.

• ESP Mastering. You can trick TESCS into letting you work with plugins as if they were masters. This can be done using a fairly easy bit-flipping method in Wrye Bash or a more cumbersome bait-and-switch method (also using Wrye Bash). It works by temporarily turning an ESP into an ESM so TESCS will let you to establish dependencies on it. See ESP Mastering for details.

• ESP Patching. This involves using TES4Edit to directly create an add-on "patch" plugin or using TES4Gecko to create a patch file based on the differences between the original and your changes. This works best when you're not adding any new content to the source originals (i.e., you're just altering values in existing records, such as giving all mudcrabs more health or making certain weapons do more damage).

Each of these methods will be explained in greater detail when this tutorial is completed. For now, here's one of the earliest methods.

ESP Patch De-Isolation Using TES4Gecko

Here is a simple scenario where it makes a lot of sense to take advantage of mod "de-isolation" to preserve your changes in a separate plugin.

Consider this question:

I'm thinking of changing Oscuro's Oblivion Overhaul to add the War Scythes (which were left out at the last minute before the release of OOO 1.3) to some of the leveled lists, but I also know that a new version of OOO is coming out soon. Is there any conceivable way to have the changes transfer over to the new OOO (1.32) when it gets released? Some creative way of merging the old and the new or something? I don't really want to go and take the time to make the changes if I'll just end up having to do them again when the new one comes out.

Yes, there is a way. It's called de-isolation. This will keep your changes in a separate plugin so it won't be lost when OOO 1.32 comes out. However, these instructions are fairly specific to OOO 1.31, which used one large ESP file (OOO 1.32 uses a split ESM/ESP pair).

Start by making a copy of OOO, called something like OOO_scythes.esp. As long as you're just altering things that already exist in OOO, make all your changes there. If you need to add anything new to it, then hold back on making those changes until later in the process.

Once you have the changes done, make a backup copy of your changed plugin just in case something goes wrong, then use TES4Gecko to Ignore everything except the changed entries (you can use TES4Gecko compare to help here). You can quickly Ignore large blocks of stuff by simply doing group-level ignores on record groups you know you don't need.

When you're done, save the plugin, and you'll see all the Ignored entries vanish.

Next, fire up Wrye Bash, right-click OOO_scythes.esp, select Add Master from the context menu, and pick any other ESM file you can find (since OOO is currently an ESP only). After doing that, re-select your mod, look in the dependencies window (small pane in lower-right of screen), find the master record you need to change, right-click it, select Change To, and go find Oscuro's_Oblivion_Overhaul.esp

This will make your OOO_scythes.esp dependent on the main OOO ESP and will make your changed scythe records override the normal ones.

Alternately, you can accomplish the last part in a different way if it makes more sense to you. In Wrye Bash, right-click the Oscuro's_Oblivion_Overhaul.esp, select Copy To ESM, and then use that new ESM for the Add Master step, then right-click your mod again and select ESPify Masters.

When you play, you'll of course want to put your OOO_scythes.esp after OOO in the load order, but that's really all there is to doing it.

This way a single OOO_scythes.esp can, for example, be used with either the FULL or LITE versions of the Oscuro's_Oblivion_Overhaul.esp, and it will almost certainly be completely compatible with future versions of OOO -- only minor adjustments would be needed if future versions of OOO make new changes to those specific items (or the leveled lists you added them to), but at least you don't have to worry about changes anywhere else in OOO.

Now, if you want to add some new content as well, and you want to make sure it doesn't have a problem when the next version of OOO comes out, then you'll need to take a few more steps after this.

I'll get to that on the next update of this tutorial.

One other possibility worth considering if you're only making changes and not adding anything new. Once you've finished making all your changes and chopping the plugin down to only include the records you changed, you can make it into a patch file. To do this, all you have to do is change the file extension to .ESU instead of .ESP. This allows TES4Gecko to recognize the file as a patch and you can use the Apply Patch function to add your changes back into OOO after the update is released.