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About this mod

An automation tool used to optimize BSAs, meshes, textures and animations. It allows quickly porting an Oldrim mod to Skyrim Special Edition.

Permissions and credits
Cathedral Assets Optimizer

Cathedral Assets Optimizer is a tool aiming to automate asset conversion and optimization for Skyrim Special Edition. It is an open source project.


General :
  • All optimization options can be performed on just a single mod or multiple mods at once.
  • You can convert, optimize, and pack your entire mod install into BSAs with a single click!
  • Each option is independently configurable
  • Dry Run mode to detect what files would be processed without performing formatting changes

BSAs :
  • Backup and extract old BSAs before processing, preserving existing loose files
  • Recreate original BSAs after processing
  • Existing loose assets can be added to the archives during repack
  • Delete backups to save space

Textures :
  • Convert unsupported TGA files to DDS format
  • Uses Nifscan to detect and convert unsupported DDS formats to useable ones
  • Convert uncompressed DDS files to BC7, the highest quality compression Skyrim utilizes

Meshes :
  • Optimize both normal and headpart meshes
  • Detects headparts and applies correct settings
  • Offers three levels of mesh processing detail

Animations :
  • Uses Bethesda's Havok Tool to convert Oldrim animations to SSE format


BSAs: BSArch by Zilav
Textures: Either of the following:
Animations: Havok Tool provided with the SSE Creation Kit, found in the Bethesda Launcher.


For general use:
  • Download and extract the Cathedral Assets Optimizer archive into a new folder anywhere you wish.
  • Download BSArch and extract bsarch.exe into the (CAO)\resources folder.

If you also intend to process animations:

Use Instructions

Disclaimers :
Always make a backup of your mods.
BSA Processing is not supported when working directly with the game's Data folder.

  • Launch the tool outside of your mod manager.
  • Click Open Directory and navigate to the folder requiring conversion or optimization.
  • Select whether you're processing a single mod or several.
  • By default no options are enabled. Activate whichever you need. In "Several mods" mode only the minimum "Necessary" optimization for meshes is available.
  • For general use, recommended modes per mod manager are:
    • Kortex, MO2, Vortex : One mod or Several mods, depending on intent
    • (Note, DO NOT run CAO through these! Run it directly with your mod manager closed. Running CAO through your mod manager's launcher may cause unintended VFS-related errors.)
    • NMM : One mod
    • Wrye Bash : One mod (Several mods only with small mod setup or installed on SSD due to file indexing)
  • Once desired options are set, click Run.
  • Make a snack while you wait. BAO does automate the conversion, but speed is still determined by the number of files.

If you need help, please join us in the Modding Tools Discord server!

Optimization Settings

Modes :
  • Dry Run - Processes the selected directory without editing any assets, listing what actions would be performed. Will extract and repack BSAs if those options are selected.
  • One Mod - Processes the selected directory as the "root", expecting that the asset folders (meshes, textures, etc) are directly inside.
  • Several Mods (MO) - Processes the selected directory as if it contains multiple mod folders, each containing asset folders directly inside.

  • Extract Old BSA - Extracts any BSAs present in the mod folder.
  • (Warning. If you enable this option, the process will be considerably slowed down.)
  • Create BSA - Creates a new BSA after processing the previously extracted assets.
  • (Warning. If you enable this option, the process will be considerably slowed down.)
  • Pack Existing Loose Assets - By default, loose assets aren't packed. This option put them into BSA.
  • Delete Backups - By default, a backup of existing bsa is created. Enabling this option will disable those backups.

Textures :
  • Necessary Optimization - Converts any TGA files into DDS, as SSE cannot read these. Attempts to convert and fix any textures that would crash the game, as some older formats are incompatible with SSE.
  • Full Optimization - BC7 is the most efficient compression SSE supports, reducing VRAM usage without observable quality loss. Will also convert uncompressed textures to BC7.

Meshes :
  • Necessary Optimization - Attempts to repair meshes which are guaranteed to crash the game. Headparts are included.
  • Medium Optimization - Perform necessary optimization, and also lightly optimizes typically non-crashing meshes. This may fix some visual issues, but may also lower quality.
  • Full Optimization - Fully optimize all meshes. Only apply if standard mesh optimization ignored necessary files. May lower visual quality.

Meshes :
  • Necessary Optimization - Converts animations to SSE format. If an animation is already compatible, no change will be made.

Other Useful Tools

DDS FileType Plus: Used with Paint.Net to open and manipulate textures saved in BC7 format, such as the ones optimized by BAO. (Note: The texture's file extension needs to be changed to .dds2 to be opened, and then changed back to .dds when you're done so that SSE can properly read the file again.)
Textures Downscaler: A simple, command line, textures downscaler.


Zilav, for Nifscan, BSArch and ListHeadparts
Ousnius, for sharing the SSE Nif Optimizer code.
Opparco, for creating NifOpt, a CLI version of SSE Nif Optimizer.
Microsoft, for TexConv and TexDiag.
Feles Noctis, Hishy, and many others, for tests and advice