Skybox textures

This guide will show you how to make custom skybox textures for use in your map. For a guide on making the in-game skybox, go here.

Step 1
 Go to www.cgtextures.com and make a free account. As you can see, this site is a great resource for making your own textures. After making an account, go to the skies 360 section and select a sky.

Step 2a
 This step is all about theory so if you want you to start making a skybox, go to the next step.
There are two ways on making a skybox texture. First is to make a terrain with fog and sky using terragen or bryce. You can also use 3d max or maya but the technique is different for making a skybox texture for them.
If you want to make a skybox with terragen, go here.

    A skybox texture is composed of six images arranged in a cubic formation. There are skyboxes and skydomes. The reason games use skybox is because they are less resource intensive than skydomes. The goldsrc engine needs six textures in the gfx/env folder to be able to use in vhe. If your skybox texture name is foo for example then the textures should be named as:

footp
foobk
fooft
foodn
foort
foolf

Step2b


  I downloaded this texture from cgtextures as an example.

I downloaded the lowest quality strip version of this texture. Using a photo editing tool like photoshop or gimp, I divided the textures into six equal parts each of 256x256 dimensions. Now, convert all the textures to .tga format and remember that no matter what dimensions your skybox has, the individual textures need to have a resolution of 256x256 with a 24 bit or less colour depth.

Step3


 Now, give a name to all your textures and put the textures into gfx/env folder. Load up hammer and enter the name you chose for the skybox in the map/map properties/environment map(cl_skybox) box. Remember that the name should be the same for all the six textures and they should end up with the appropriate suffix. Se step2a for the instructions. After that, the map should successfully show the skybox in-game.

Notes:

If you are wondering how to convert panoramic textures then use bixorama or pano-stitch like programs. Bixorama is very easy to use but it is commercial software. Pano-stitch is based on a open source panorama tools.
   Additionally, you can also make a skybox for the goldsrc engine using the source engine. Go here to learn how to make skyboxes from the source engine. If you only want to make a sky 360 texture then skypaint is a great commercial software.

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Edit:
Pano2vr is also a  very good tool to convert panoramic to horizontal cross photos. Go here to get pano2vr. Its not free though.
Cgtextures.com have recently updated their skies 360 page. You need an account to buy skies but high quality samples can be downloaded for free. But they have stopped giving skies in dds format.