The 4 sides of desert
skybox stitched (for illustration, it is projected properly in game)
In GoldSrc, a
skybox is a set of 6 textures that wraps around an inverted box. In game, wherever you place
SKY texture will be rendered in its place a skybox, which is static relative to the player i.e. moving around the map doesn't shift the perspective of the skybox textures in any way.
The files for skyboxes for Half-Life and mods can be found by looking in the
gfx/env/
folder relative to the game/mod folder. For legacy WON installations, you could find them inside the
pak#.pak
files (where
#
is a number) which you can open with any software that is capable of reading Quake PAKs files like PAKScape. As each skybox is composed of 6 textures, the files are appropriately suffixed with the respective sides:
ft - front,
bk - back,
rt - right,
lf - left,
up - up,
dn - down.
The actual texture shown in game is controlled by the Map Properties setting
Environment Map (cl_skyname). The name should be same as one of the texture sets in the
gfx/env/
without the suffixes (any underscore between the name and the suffix can be omitted too.) The default is
desert
.
Custom skies can be added by adding the file set to the
gfx/env/
folder and then selected in the map properties before compiling. Each file in the set should be in 24-bit
TGA file format and 256×256px in size. While BMP files are also supported they are of the lower fidelity 8-bit kind to support older video cards of the 1990s, and thus no longer relevant in the 2020s.
To have part of the map render the skybox, texture the brushes with the
SKY texture as mentioned earlier.
3D Skybox
The term 3D skybox can mean two things:
- A regular skybox whose textures are generated using a 3D terrain generation software, or
- Another projection layer in which a miniature landscape (usually 1:16 the size) placed in an unreachable, far away corner of the level, gets projected into the playable areas of the level, similar to
SKY
but the projection shifts appropriately to match the player's position in the level.
The latter is a feature in the
Source engine. Some GoldSrc mods like Spirit of Half-Life also supports but they usually require a particular set of configurations.
See also