Lithrez is used to create and extract REZ files.
This is the explanation given in the tools regarding rezing up a file for distribution.
Lithrez is a command-line utility which can pack and unpack AvP2
'.REZ' files. You must use this to "unlock" the media, models,
textures, etc. that are contained in the AvP2 .REZ files before you
can edit them with DEdit or ModelEdit. LithRez is located in the
Tools folder and will display the following help if run without any
Usage: LITHREZ <command> <rez file name> [parameters]
Commands: c <rez file name> <root directory to read> - Create
v <rez file name> - View
x <rez file name> <directory to output to> - Extract
Options: v - Verbose
Options: z - Warn
Options: l - Lower
Example: lithrez cv foo.rez c:\foo (would create rez file foo.rez from the contents of the directory "c:\foo" the verbose option would be turned on)
A simple DOS batch file (unrez.bat) has been provided to simplify the process of unpacking the AvP2 Game resources for you. To unpack the AvP2 Game Resources, just double click on "unrez.bat" located in the Tools folder. Make sure you have at least 700 MB free space on the hard drive where AvP2 is installed before running the .bat file.
If you create your own add-ons (that you plan to distribute), you will need to store your resources in a new .REZ file (e.g., MyMod.rez). For these resources to be available to the game you must add the following line in the advanced options section of the AvP2 launcher:
(NOTE: be sure to check the "Always specify these command line parameters" check-box so these resources are always available to the game.)
Alternatively, you can add the "-rez MyMod.rez" to a string value named "Update Command Line" in the "HKEY_Local_Machine\Software\Monolith Productions\Aliens vs. Predator 2" registry key.
If you want to run custom multiplayer worlds on the dedicated server, you will have to set up a special .txt file which the server reads to find the world path:
1) Make a text file named "customrez.txt" in your AvP2 folder.
2) Edit the customrez.txt file, adding the names of the custom .rez files you want the server to load when you launch the dedicated server. You have to follow the format
For instance, if I have a "coolguns.rez" file with altered weapon models and a "fastpred.rez" file with a modified characterbutes.txt attribute file and I wanted my server to use both of them, my customrez.txt would look like this:
It is important to note that if the .rez files share contained files, for instance if both coolguns.rez and fastpred.rez had a modified weapons.txt inside them, the second one in the list will be the one that is used. So in the example above the server would end up using the weapons.txt attribute file in fastpred.rez even if coolguns.rez had one as well. You should only include new resources in your .REZ file. For example, if you created a new DeathMatch level (MyCoolLevel) that was based on existing AvP2 textures, you would only need to include the MyCoolLevel.dat file in your add-on .REZ. Your resource folders might look like something like this:
To create the MyMod.rez file you would run LithRez as follows:
GameDirPath\Tools\LithRez.exe cv MyMod.rez c:\MyMod
I might snap some pictures of how I have it set up if I get the time.