Fake 3D skybox: As my giant message above states, this is just one solution to the problem where a map has too many brushes and fails to compile. What this tutorial will explain to you is how you can take your existing 3D skybox and convert its projected image in your map to a standard 2D skybox image thus eliminating the need for the 3D Skybox and lowering your brush limit to one which will allow the map to compile.

Downside to this method is that the objects in the skybox will not move based on your perspective as they do with a standard 3D skybox, ie the blue square is an object in the 3D skybox:

3D Skybox
Position 1	30 Metres Left
2D Skybox
Position 1	30 Metres Left

Now you can see that this would only look good if the objects in your 3D skybox are fairly fall away from the players perspective to limit this visual issue.

The Method All you need is a vmf file containing nothing but your 3D skybox - scaled or not doesn't matter and the same light settings your using in the playable map.

Nothing else needs to be done with the map file itself, just compile the map as you would any other and load it in CS:S.

I'd recommend setting your graphics to as high as possible - Anti-Aliasing etc - as it will improve the quality of the skybox images you will be creating.

Once your map is loaded join the spectator team and position yourself in the level as you want the skybox to be displayed (Desired perspective). I'll use the CS_Milita Skybox as an example here:

Now run some cubemap specific commands - almost like buildcubemaps but different.

In Console Type:

mat_envmaptgasize 512
envmap

[...]\counter-strike source\cstrike\cubemap_screenshots\

The images already come with the standard bk up dn lf rt ft post-fixes that skyboxs use so that saves some effort.

Converting to VTF & VMT Skybox files The quickest and easiest way to convert these to VTF files without having to download any programs etc is through vtext.exe thats in the SourceSDK.

Navigate your way to the following path:

[...]\sourcesdk\bin\ep1\bin\

You'll see a vtex.exe program near the bottom of the folder. Start a new window but keep this one open as well.

In the new window go back to the folder holding your tga files for the skybox and copy them to this folder location:

[...]\sourcesdk_content\cstrike\materialsrc\skybox\ *You may have to create the skybox folder.

Now create a new TXT file with the following code in it:

"skybox" "1"
"nomip" "1"
"nocompress" "1"

mapnameup.tga mapnameup.txt ...

Now select each of your TGA files and drag them onto the vtex.exe in the other folder window. A Command prompt window will pop up and it will run through each of your images and convert them to VTF files. The complete files will be in the Skybox folder in CS:S already so you'll need to go to that path now to finish this tutorial:

[...]\counter-strike source\cstrike\materials\skybox\

You should see your VTF files sitting there now, if not check to make sure you had SourceSDK running with CS:S selected in the game config, then redo the vtex.exe step.

However, the last thing missing are the .VMT files so you'll need to create all 6 of those as well. Create a TXT file in the folder and inside it place this code:

"UnlitGeneric"
{


"$basetexture" "skybox/filename" // ex:  cs_militaup
"$nofog" "1"
"$ignorez" "1"


}

If you get purple/black textures in-game check that the .vmt files are not called mapnameup.vmt.txt

Repeat the above step about properly saving it so remove the extra txt on the end or change your folder view options to show known filetypes so you can just rename it from the folder explorer window.

Now of course all you do is edit the map properties to include your newly created custom skybox texture and remove the 3D skybox.