A simple mod example

Getting started
Modding S.T.A.L.K.E.R. is a rewarding experience because it allows you to bend the extremely atmospheric game to your will. With enough patience and will power, (Knowing Russian helps) you can figure out how to change the most complex "settings" in the game to fit your new world. However, we are not at that step yet. We are going to start nice and simple and work our way up through other tutorials. You will need quite a few tools before you begin on your first mod.

Note: This tutorial is designed for Shadow of Chernobyl, but can be applied to Clear Sky and Call of Pripyat in exactly the same way.

Tools
Database Extractor

Notepad++ (Optional, Windows Notepad works fine, but you will thank me later)

STALKER - Shadow of Chernobyl patched to at least 1.005 (1.006 is mostly an optional patch, it only changes Multiplayer stuff, nothing you will be editing), or STALKER - Clear Sky patched to 1.5.10, or STALKER - Call of Pripyat patched to 1.6.02, depending on which one you wish to mod.

A good amount of space on your Hard Drive. (10 gigabytes free is a must for lots of wiggle room and backups)

Understanding extraction and mod structure
Extract all the database archives into a separate folder on your desktop. Name it gamedata_original. Now, there is so much to change! Create a new folder in your X:\Program Files\THQ\S.T.A.L.K.E.R. - Shadow of Chernobyl (X for your drive letter) and call this new folder gamedata. If you have not already browsed through your gamedata_original folder, do so now. So many files and sub-directories! Whenever you edit a file, Notepad ++ will create a .bak of the original in the folder it was edited so you always have the file as it was when it worked (or before changes). To make this .bak work, all you must do is rename the extension back to .ltx or whatever it was before.

If you can't see extensions and are on Windows XP, open up a folder and go to Tools - Folder Options and click on the View tab. Uncheck hide extensions for known file types.

Editing your first file
Notepad++ and Windows Notepad are only capable of editing essentially word files. These extensions include .ltx and .xml and .script. (Notepad++ handles .xml and .script files much cleaner than Windows Notepad) An easy first change to STALKER is changing how much you can carry, your weight limit. When STALKER was first released there were mods that were entirely based on just doing that. It isn't any big mystery how it's done now, but it is still sometimes done improperly. There are a total of 3 lines of code that need to be edited to make the new weight limit official. 2 of them are in actor.ltx and one of them is in system.ltx:

Note: If modding Clear Sky or Call of Pripyat instead of SoC, the Addresses will be the following respectively:
 * C:\Program Files\THQ\S.T.A.L.K.E.R. - Shadow of Chernobyl\gamedata\config\creatures\actor.ltx
 * C:\Program Files\THQ\S.T.A.L.K.E.R. - Shadow of Chernobyl\gamedata\config\system.ltx


 * C:\Program Files\Deep Silver\S.T.A.L.K.E.R. - Clear Sky\gamedata\config\creatures\actor.ltx
 * C:\Program Files\Deep Silver\S.T.A.L.K.E.R. - Clear Sky\gamedata\config\system.ltx
 * C:\Program Files\bitComposer Games\S.T.A.L.K.E.R. - Call of Pripyat\gamedata\config\creatures\actor.ltx
 * C:\Program Files\bitComposer Games\S.T.A.L.K.E.R. - Call of Pripyat\gamedata\config\system.ltx

You see now both of these files have gamedata\config in common, so browse to your STALKER gamedata folder which is looking very empty right now, and create a new folder called config inside.System.ltx will land right in there, but actor.ltx goes a bit deeper. Create another folder inside config and name it creatures. Keep the gamedata folder open and go to the gamedata_original folder. Browse first to gamedata_original\config and copy system.ltx to your STALKER gamedata\config folder. Open it up and you should see something like the first Image.

Hit Ctrl+F and search for weight and you will hit upon a line with max_weight in it. Change the value to say 120 or whatever value you want. 1 = 1 kg in game. Save it, you are done with system.ltx.

Now copy over the actor.ltx from gamedata_original and paste it in gamedata\config\creatures. Open it up and you will see something resembling the second image.

Search for max_item_mass. It's visible without searching with Ctrl F, around line 20. Once you find that, change the number it equals to 120 or whatever you changed the number in system.ltx to. Now do a search for max_walk_weight. This one is up to your judgment. The other two are bound together to control how much weight you can move this while being able to run. If you want to just be able to carry 120 kg and then stop dead at that limit, you can also put this number to 120 kg. However, if you would like to be able to carry stuff after 120 kg but not be able to run, just walk, set it to something like 140.

This means you can carry stuff and run up to 120 kg, but you can also carry stuff and still be able to at least walk up to 140 kg. Save it and exit.

Setting your mod to run
<p style="line-height:19px;color:rgb(0,0,0);font-family:sans-serif;">STALKER works by basically interrupting original content with your edited stuff. To make this happen, look inside your STALKER root directory and you will find a file called fsgame.ltx. Open it up and it should be the second line you need to edit. It will appear (If you haven't edited it before) like this: $game_data$ <span class="sy0" style="color:rgb(0,0,102);font-weight:bold;">= false|true|$fs_root$|gamedata\ <p style="line-height:19px;color:rgb(0,0,0);font-family:sans-serif;">This is telling the game to ignore everything and just read the game files in the database archives. We need to change that. Change that line to appear as: $game_data$ <span class="sy0" style="color:rgb(0,0,102);font-weight:bold;">= true|true|$fs_root$|gamedata\ <p style="line-height:19px;color:rgb(0,0,0);font-family:sans-serif;">Now it will load any files you have in the gamedata folder instead of the same named files in the databases. Simple? Save and exit. Start up STALKER and you can enjoy your new weight carrying limit.

<p style="line-height:19px;color:rgb(0,0,0);font-family:sans-serif;">Also, Clear Sky and Call of Pripyat in some cases don't appear to need this edit to enable mods, but it is safer to do so, and will guarantee that the mod will work first time.