UBT | Unity Bundle Tool

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UBT | Unity Bundle Tool

Unity Bundle Tool is a software made by my friend, SowwyItsAnAlt, which I have been using in my repacks for a few months. With her permission, I have rewritten and polished the code and made a new executable which I am sharing here.

The function of this tool is the ability to decompress compressed Unity Asset Bundles and then recompress them to a close enough point in which a patch is possible (& viable!). I like to use HDiffZ because it gives the smallest patches. XDelta should work just fine (patch creation is significantly quicker than with HDiffZ although the patch file will be larger).

UBT is based on AssetTools.NET by nesrak1 and has compression support for both LZ4 and LZMA compression.

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 █ Unity Bundle Tool | 10/02/21 █
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 Usage: UBT.EXE <options> <infile> <outfile>

 Options:

     -i       : List information about bundle file (only specify <infile>).
     -d       : Decompress bundle file.
     -c       : Compress bundle file (must specifiy use of LZ4 or LZMA).
     -credits : View credits.

 Example usage:

 UBT.EXE -i data.unity3d
 UBT.EXE -d data.unity3d decompressed_data.unity3d
 UBT.EXE -c lz4 decompressed_data.unity3d data.unity3d
 UBT.EXE -c lzma decompressed_data.unity3d data.unity3d

To prove just how well this tool works, I will demonstrate on the game "Poly Bridge 2" (which I do recommend you all try if you enjoy a good puzzle like myself). This game contains "data.unity3d" which is compressed via LZ4. The steps are:

1. Decompress the bundle
2. Compress the decompressed file using the same compression algo as what the original bundle was compressed with
3. Use your patch program of choice to create a patch file between the new compressed file and the original compressed bundle.
   
   
   
   As we can see from the above image, the new file is so similar that our HDiffZ patch is less than 1mb in size! Now, in your repack installation, you simply include the decompressed file and compress it then patch it using the patch file after the archive is extracted. Easy!
   
   Of course, you don't need to patch the file, since Unity will read the file regardless - compressed or decompressed. The patch is simply for a 100% CRC perfect repack.
   
   Highlighted above is the function of the -d and -c option. Using -i will give the file size in bytes, MD5 and compression type used on the input file.
   
   This is a standalone tool and NOT for use with FreeArc.

Have fun and enjoy. Happy New Year.