TF2/Modifying the Mission Briefing

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The mission briefing, shown to players before they enter the match, is set automatically for Basic Capture the Flag and Control Point games, just by putting the right goal entities on the map. Custom ones can be done, but how? It is not possible to do so via a tool such as Hammer, but you can edit the localized texts in the directory where you map is in.
Writing a briefing
In the directory where your .bsp is:
"..\Program Files\Valve\Steam\SteamApps\_Username_\Team Fortress 2\tf\maps\"
Create the localised map .txt briefing files. You can also extract them from the TF2 .gcf with GCFScape and rename them for your map. So the maps directory should look like this:
mapname.bsp mapname_danish.txt mapname_dutch.txt mapname_english.txt mapname_finnish.txt mapname_french.txt mapname_german.txt mapname_italian.txt mapname_japanese.txt mapname_korean.txt mapname_norwegian.txt mapname_polish.txt mapname_portuguese.txt mapname_russian.txt mapname_schinese.txt mapname_spanish.txt mapname_swedish.txt mapname_tchinese.txt

For example: If your map is named cp_factory, then your .txt files shuld appear like this:
cp_factory_english.txt
In each of those, is the briefing text displayed for your map, in the named language. While the above is listed, you won't have to make a .txt file for each language.
Adding Custom Map Images
In order for your custom map to have 2 working Menu Photos it needs 2 files in following directory:
C:\Program Files\Steam\steamapps\<account_name>\team fortress 2\tf\materials\vgui\maps
These 2 files are:
- menu_photos_mapname.vtf
- menu_photos_mapname.vmt
Creating the VTF file
Making a TGA image
- Take a few screenshots of your map depending on how many you want to show. Make sure they look good in a 512x512 resolution.
- Create a 512x512 pixels TGA with a black blackground, then paste your screenshots into it. Edit the alpha channel of the image so it hides the black background. Note that you will require an advanced image editor to do this, such as Adobe Photoshop. Save the file as menu_photos_mapname.tga in 32 bit and uncompressed.
- Copy and paste your "menu_photos_mapname.tga" in following directory: C:\Program Files\Steam\steamapps\<account_name>\team fortress 2\tf\materialsrc
Preparing VTEX
We will create a vtf from the tga using vtex.exe. Let's take some time to set it up.
- Go to the following directory and create a desktop shortcut of the vtex.exe: C:\Program Files\Steam\steamapps\<account_name>\sourcesdk\bin\orangebox\bin
- Go Properties on the vtex.exe shortcut and append the following parameters to the text in the Target field:
-game "C:\Program Files\Steam\steamapps\<account_name>\team fortress 2\tf" -nop4
Converting the TGA to VTF
Drag your tga you created onto the vtex.exe desktop shortcut. The vtex.exe will create a menu_photos_mapname.vtf in the following directory: C:\Program Files\Steam\steamapps\<account_name>\team fortress 2\tf\materials
Creating the VMT file
Open notepad and paste the following lines of code into it.
"UnlitGeneric" { "$basetexture" "vgui\maps\menu_photos_mapname" "$translucent" 1 "$ignorez" 1 "$vertexcolor" 1 }
Replace 'mapname' in "$basetexture" "vgui\maps\menu_photos_mapname" with the name of your custom map. For example, if your map is called ctf_2fort, then it should read
"$basetexture" "vgui\maps\menu_photos_ctf_2fort"
Save the file as "menu_photos_mapname.vmt".
Place your files in the proper directory
Move your "menu_photos_mapname.vtf" and "menu_photos_mapname.vmt" to the following directory:
C:\Program Files\Steam\steamapps\<account_name>\team fortress 2\tf\materials\vgui\maps
If you correctly edited the Alpha Channel of your tga and did all the other steps like mentioned, your 2 map screens will be displayed on the Objective Screen on Map Start!
Conclusion
It is advised to pack the files into your map using BSPZip, PakRat or a similar program, otherwise, your files won't be downloaded while connecting to a server running the map, hence your briefing will not appear on other clients.