Although probably not as fun as level design, making skyboxes can add a lot to the experience of creating a map, as well as the atmosphere and gameplay of a level. Skyboxes can be loaded with the "loadsky" command, followed by the path to the files. The "loadsky socksky/desert" command for example will load the desert skybox located in the folder packages\socksky. You can browse to this folder and view the six images that compose the panorama you see in game. This guide will focus on the process of creating a skybox with several software rendering packages.

Many of the Cube and Sauer skyboxes were created with Terragen. You can find a detailed step-by-step tutorial by googling for "Terragen skybox" and "Lloyd M". In Terragen, as well as in the other packages we're about to use, there are a few basic rendering parameters that need to be set for each of the six images so they can blend seamlessly. In Terragen v0.9 (the version used here), all of the parameters can be accessed from the Rendering settings window. Images need to be square, so first click on Image size and set both height and width to 128, 256, 512, 1024, etc. Click Camera settings and set Zoom / Magnification to 1. Below is the camera orientation, which you can set individually for each image before rendering:

skybox_LF -- pitch = 0, head = 0
skybox_RT -- pitch = 0, head = 180
skybox_BK -- pitch = 0, head = 90
skybox_FT -- pitch = 0, head = 270
skybox_DN -- pitch = -90, head = 0
skybox_UP -- pitch = 90, head = 0

All images must be saved in jpeg format, the last two images (filename_up and filename_dn) must be flipped horizontally and vertically. So after rendering you should edit the images in image processing software like Adobe Photoshop, The Gimp, etc. and make the needed changes. You could also add stuff and use a smudge tool or other tools to make additional corrections.

Terragen also allows to make a simple six-frame animation script to turn the camera and render the files automatically as opposed to editing parameters every time you render. Here's an example script (can be saved in a text file and then loaded in Terragen from the Terragen->Execute script menu):

InitAnim "c:\folder\filename", 1
CamP 0
CamH 0
FRend

CamH 180
FRend

CamH 90
FRend

CamH 270
FRend

CamH 0
CamP -90
FRend

CamP 90
FRend

If you are not comfortable with editing each image individually, a batch file could be used to convert the images produced by the above script automatically. Windows batch files are text files that have the .bat extension and can be used to execute several commands. You can place the batch file in the folder where the images reside. When you double-click the file (filename.bat), the sequence of commands it contains is started (and hopefully, will end in a few seconds). If you have ImageMagick installed these commands can be, for example:

convert filename0001.bmp skybox_lf.jpg
convert filename0002.bmp skybox_rt.jpg
convert filename0003.bmp skybox_bk.jpg
convert filename0004.bmp skybox_ft.jpg
convert -flip -flop filename0005.bmp skybox_dn.jpg
convert -flip -flop filename0006.bmp skybox_up.jpg

This tutorial is not finished. Two more sections are planned, with info on using Blender and POV-Ray.