Fallout 3
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Ehamloptiran Sheson and FO3Edit Team

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About this mod

An almost one-click LOD generator for Fallout 3

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Objects LOD generator for Fallout 3

This tool allows to generate Objects LOD for worldspace(s) by scanning all mods in load order that add visible from distant objects. Trees LOD generation is also available, though not recommended to use (read technical description down below)

Make sure to install FO3LODGen outside of Program files folder, somewhere with write access rights, or run as Administrator.
Install FO3LODGen resource pack using your mod manager, and any optional trees LOD packs if needed over it.
Activate FO3LODGen.esp in load order.
Run FO3LODGen.exe, wait for it to load your plugins, then select worldspaces to generate LOD (by default only Wasteland worldspace is selected, right click in the list to select all/none), and click Generate. Wait for it to complete, you can watch progress and check possible errors in messages list. When finished, close the program manually.

Mod organizer users:
Install FO3LODGen in a directory of your choice. Add FO3LODGen.exe to MO executable list by clicking the gears button and then browse for FO3LODGen.exe to fill the "Binary" field. Add a dedicated output directory by adding -o:"C:\FO3LODGenOutput" to the "Arguments" field. Once LOD generation has completed copy/move files from the dedicated output directory to the game data directory or into a custom mod (recommended for load order management) in MO.

How LOD works in Fallout 3

LOD in general is what you see in the distance, beyond the uGridsToLoad setting value. Fallout uses static LOD which means that LOD information is prebuilt and doesn't change when mods modify objects in game. Some mods include updated LOD files to address this issue, but they are rare and usually incompatible with each other and require compatibility patches of their own. Those LOD files are generated with GECK which is quite complex procedure unaccessible by majority of users. FO3LODGen tries to address this issue by providing a simple one-click automated LOD files generation for the current load order of user, taking in account all mods that have content visible from distance.

Fallout LOD is divided into 3 parts:

Terrain (landscape) LOD - the shape of landscape in the distance, contained in files
where <Worldspace> is the name of worldspace.
Those files are rarely updated since mods almost never change terrain shape or changes are minimal and would be hardly noticable when far away. Terrain LOD files are generated by GECK, FO3LODGen doesn't create them.

Objects LOD - any static object: houses, shacks, rocks, cliffs, etc contained in files
Both terrain and objects LOD files are actually large nif macromeshes that can be opened with NifScope. FO3LODGen generates objects LOD files from separate small lod meshes for each static object in game that have them, they have the same name and location as the full detail model with _lod.nif suffix.

Trees LOD - images of trees in the distance, contained in files
Textures\Landscape\Trees\TreeDeadLod.DDS and TreeSwampLOD.DDS (for Point Lookout DLC), atlas textures
Unlike previous LODs, DTL files are not meshes, but just a binary data that tells the game what tree type, where to display, and with what scale. File with LST extension defines tree types: width and height in game, and position of a particular tree LOD image on atlas texture. "Atlas" means that there are several separate images located inside a single image. Trees in the distance are just flat images of trees displayed from atlas texture. The usage of single texture in Fallout for all trees is performace friendly, but unfortunately very problematic for mods that change tree models or add new ones. To update LOD images, even if it is only a single tree, the mod must include the whole atlas texture along with images for all other trees even if they are unchanged. The other problem of trees LOD is that a single atlas texture is used for all worldspaces. Also trees in the distance disappear briefly when you approach them, making trees LOD system in Fallout redundant.
Instead of that, FO3LODGen allows to generate LOD for trees as objects LOD to address above issues. Install provided resource pack and generate objects LOD for all worldspaces to make all trees as objects.
DO NOT GENERATE Trees LOD unless you know how it works, read TES5LODGen description for more info since trees LOD system is the same in Skyrim if you are really interested.

LODGen options

FO3LODGen generates LOD only for worldspaces that have existing file LODSettings\<Worldspace>.dlodsettings, it is created when building terrain LOD in GECK. It containes the cell coordinates of the south west corner of worldspace and they are needed to properly name generated LOD files to align with terrain LOD files.

Uninstalling generated LOD

Just delete files mentioned above for objects LOD (and trees LOD if used), no other changes are made during LOD generation.