Fallout 3 working edited textures
I've just discovered how to successfully load a modified texture into Fallout 3 and get the game to recognize it, and since this appears to be a pretty significant step in this arduous task of modding FO3, I'm going to make a detailed description of how this was done. It's not too divergent from the process that Oblivion modders are used to, but since resources for FO3 are very limited at the moment I will give step by step instructions on how to do this (I'll try to be as detailed as possible for non-Oblivion modders).
First off you will have to know the file name and the file path of the file that you want to replace. For this you will have to extract the files from the Fallout 3 Texture .BSA (Bethesda Softworks Archive). Currently the only person that I am aware of to have created an archiver/.BSA extractor that will work on the *texture* archive is ScripterRon from the official Bethesda forums. He has uploaded his program to Fallout 3 Nexus.
There is another method going around where you can use the BSA Commander program along with a hex editor to extract the files from any of the other .BSAs, however this will not work with the texture .BSA due to a difference in protocol. In effect, the files (once extracted) will end up being 0 KB and will contain no information.
Once you've extracted the .BSA you'll be able to see that the file paths are identical to Oblivion's for the most part. Once you've made the changes to the desired texture you'll want to do the following:
1.Save the file with the exact same name and in the same format as the original file that was extracted from the .BSA.
2.Open your 'Fallout 3' folder, and inside you will find a folder called 'Data'. From here you will want to create an identical file path to your newly edited file as to the path of the file you extracted from the .BSA. This step is exactly the same as when you want to replace a texture or file in Oblivion. For example, if you edited a texture from the .BSA called headhuman.dds, that had this filepath:
You will want to make a series of folders starting in your 'Data' folder to your newly edited file.
3.Now that you have the file path set up, you need to create an ArchiveInvalidation.txt file in your 'Fallout 3' folder, not the data folder!. ArchiveInvalidation is a process that keeps the game from loading the original texture file found in the .BSA, and by means of the code inside redirects the game to load your shiny new edited file. It's really complex, and this is a simple workaround for the problem until a better one comes. For more information on this subject and how it was used in Oblivion, take a look here at devakm's ArchiveInvalidation page.
4.Inside the ArchiveInvalidation.txt file, you will simply want to place the file path of the newly edited file, starting from the folder inside the 'Data' folder. Here's an example, using the file I had mentioned earlier:
NOTE THE DIRECTION OF THE SLASHES. Also, if you want to list multiple files, just hit enter and continue to list the file paths, each one on its own line and then save the text file.
5.Open your 'My Documents > My Games > Fallout 3' folder. Inside you'll see a .ini file named FALLOUT.ini. Open it, and about 80% of the way down you will see a subheading titled [Archive] and a line that says:
You'll want to change this to equal 1 instead of 0. Once the change is made, save the file and close it. If you did everything correctly (and there's a lot of room for error if you're new to this kind of thing), then when you load your game up it should load your edited texture.
PM me if you have any trouble, or just have questions regarding this process.