A tool for repacking .lvl files from SWBF (2004) and SWBF2 (2005) to decrease their size. Potentially to over half their original size.

How it Works

First a quick overview of the structure of the game's PC textures

• tex_
  • NAME name of the texture
  • INFO list of format variants
  • FMT_ a format variant of the texture
    • INFO format, resolution, mip count, type, detail bias
    • FACE a texture face (only cubemaps have multiple faces)
      • LVL_ a mip level
        • INFO mip index, BODY size
        • BODY texture data
      • LVL_ repeats for each mip
    • FACE repeats for each texture face
  • FMT_ repeats for each format variant

There are two things to note here the first is

• INFO list of format variants

and the second

• FMT_ repeats for each format variant

Each texture can effectively have multiple copies of itself, each in a different format. Back in the day the game used this (presumably) pick the most suitable format at runtime based on the user's GPU and possibly other things.

Not every texture has multiple formats but when one does it usually (but not always) has 3, a BC1/BC2 compressed copy, a 16-bit copy and a 32-bit copy. These days though the game will by default almost always pick the compressed one to use. That leaves a total of 6 bytes per-pixel of wasted data being stored.

And that is what this tool does. It edits the tex_ chunks in the .lvls and removes all but one format. By default it leaves the 32-bit format (if present) but it can be told to prefer leaving the compressed formats, further saving space.

Luminance formats like D3DFMT_L8 and D3DFMT_A8L8 are always preferred if present.

Results

Below are the results from repacking the GoG copy of the game. Sound and movies were excluded.

Method	Size	Ratio
Original	2041.655 MB	1.0
Repacked	1062.974 MB	0.52
Repacked Prefer Compressed	833.532 MB	0.41