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 or alter 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 and Patching

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 be unable to find the internal references to connect it back to the ESPs you had loaded before, so 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.

• 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 is explained in greater detail below.

ESM Mastering

Many large mods use ESM Mastering to get around the limitations of standard plugins. However, creating your own master files can be tricky in some cases, so it's not generally recommended unless you have a strong need to do so.

Even though master files are generally supposed to only contain new content, this rule can sometimes be ignored if you really have a need to do so. Master files can in fact both use and modify content from other masters, such as Oblivion.esm, as long as they don't alter any cells (especially exterior cells) in another master.

If your mod adds a lot of new content but doesn't alter any standard Oblivion.esm cells, then it can probably be turned into a master. This makes it easy to then offer add-on option modules to extend or tweak your base master. However, you should be careful about such decisions since master files don't have the same load-order flexibility as normal plugins (masters always load before plugins).

If your mod adds a lot of new content and needs to alter cells in another master, then you probably need both an ESM (for the new content) and an ESP (to connect your ESM to Oblivion.esm). For example, if you create a new worldspace and place it in a master file, then you should use a separate plugin to connect your mastered worldspace to Tamriel. The Split Plugin feature in TES4Gecko can help in situations like this.

The process for creating a master file is simple using either Wrye Bash or TES4Gecko:

• In Wrye Bash, go to the Mods tab, right-click on the plugin you want to convert, and select Copy to Master.

• In TES4Gecko, click the Convert to Master button, select the plugin you want to convert, and click Open.

Either of these methods will give you a new file named MyPlugin.esm (assuming the original was MyPlugin.esp).

Now you can launch TESCS, select your new master, and start creating plugins based on it.

ESP Mastering

In many cases, you may not have the option to distribute your own master file. This is especially true if you don't have control over the original plugin, as with the official DLC mods. In a case like this, ESP Mastering or ESP Patching can be used instead of ESM Mastering. Once you head down this road, you may want to consider whether ESP Mastering or ESP Patching is a better solution.

ESP Mastering is usually the best choice when you want to add a significant amount of new content to an existing plugin without storing your changes in the original file. On the other hand, ESP Patching is usually preferred when you mainly want to tweak existing content in the original.

For example, if you wanted to add new enemies and dungeon levels to the Knights of the Nine DLC mod, then ESP Mastering is the way to go because you're adding a bunch of new content. If you just want to alter the existing enemies and dungeon levels in KotN, then ESP Patching is probably a better solution.

See ESP Mastering for more details.

ESP Patching

This works best when you're only changing existing records in another plugin.

Adding more details here.

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.