Cell Offset Generator - NVSE

What?

I know right? What?

Today we will learn about how plugins work, how Bethesda uses them, and how game is loading cells.

As you probably noticed, we have 2 plugin variants here in New Vegas land - Master and uh, non-Master (ESM + ESP, fun fact: before Skyrim, extensions don't do anything).

What's the difference?

ESPs are an unoptimized, essentially debug, variant of plugins, meant purely for development purposes. Which is why (vanilla) GECK creates them, and why the game doesn't ship with them. What makes them so bad? References in ESPs are persistent, always loaded into memory, inefficient. In addition, game is deliberately coded to skip various optimizations for ESPs, or to ignore them completely (Skin textures say hello). They can even break the game completely with some form types (example, navmeshes).

Okay, okay we get it, all our mods are badly made then and all, get to the point. So, what, ESMs are optimized in comparison?

Yes and no. They are the proper game data format - waste less memory, work as expected etc. But... by default they are not optimized-optimized.

Wall I already downloaded the mod please just say if it will break my modlist or not

You see, Bethesda has a special optimization pass for plugins that is applied when creating ESMs. You probably didn't know about this, because it's locked behind Version Control mode in GECK. A mode that's so obscure, and so Bethesda-specific, that setting it up for an average person is just a nightmare - no wonder only 2 FNV mods in existence use it.

I beg you, get to the point

What does that optimization do? It creates cell offset data for the plugin. What is that, you may ask. You see, exterior cells (and most things inside them) are not loaded on game launch like most other forms. No, no - they load in game, while you move around. This obviously means that game has to read plugins mid-gameplay.

And here's the issue: game has no clue where cells are in the file, or even if the cell it wants to load, is in the file.

This means it has to just scan the whole file, looking for a cell that may as well never exist. The larger the file, the longer it takes. The more files you have, you guessed it - the longer it takes.

Cell offsets resolve this issue - plugin stores arrays of offsets that point to where each cell is in said file, so game can immediately know if a plugin contains a cell, and where to go in order to load it.

How bad is it? Without offsets, I've seen seek times as long as 20 milliseconds, per file (Mainly FalloutNV.esm itself)! The cell loading code works somewhat like this:

Loop through all plugins that have the worldspace form that contains the cell we want to load, searchi