View source for Skybox (GoldSrc)

{{cleanup}}
[[Image:Sky desert GoldSrc.png|256px|right]]
Skyboxes in {{gldsrc|3}} are simple "cubemap" textures that display in the background behind the level.
{{bug|Skyboxes are always filtered in OpenGL mode with {{code|GL_LINEAR}}, regardless of {{code|GL_TEXTUREMODE}} setting ([https://github.com/ValveSoftware/halflife/issues/2606 relevant issue on GitHub])}}


== Adding sky to a map ==
Simply texture a [[world brush]] (not a [[brush entity]]) with the [[tool textures (GoldSrc)|{{code|SKY}}]] texture.

In-game, the skybox will be seen ''through'' each surface that {{code|SKY}} is applied to. 

{{code|SKY}} brushes do ''not'' need to be box-shaped.

{{note|Ideally, your skybox should somewhat "wrap" around your map such that there is only a very small/zero amount of space between the play-space and the skybox itself, though it's usually not necessary to have the skybox "hugging" the bounds of the map to achieve reasonable compile times. Leaving some visible space between the playable space and the skybox can improve gameplay and world believableness.}}
{{warning|You should avoid making a skybox by drawing a big hollowed out cube with the SKY texture around your map. This can drastically increase VIS compile times.}}

== Changing the displayed skybox ==
[[Image:Sky_change_JACK.png|right|350px]]

By default, no skybox is defined, so GoldSrc defaults to the {{code|desert}} skybox. You can change it by setting the skybox name in Hammer's Map Properties dialog. With the correct map opened, follow these steps:
# Go to the [[Hammer Map Menu|Map menu]] 
# Choose '''Map Properties...''' from the drop down list
# In the Object Properties window, select the '''enviroment map (cl_skyname)''' field.
# Enter the name of the skybox you wish to display. 
{{clr}}

== Creating a Custom 2D Skybox Texture ==
Skybox textures in GoldSrc MUST be 256x256, and they follow the same naming convention as Source, as so:
 <skyname>BK
 <skyname>DN
 <skyname>FT
 <skyname>LF
 <skyname>RT
 <skyname>UP
Both TGA and BMP images are supported, but TGA is recommended for quality and compatibility reasons.<br>
Software mode defaults to BMP skyboxes, and reads the TGA version if a BMP version is not present.<br>
OpenGL mode defaults to TGA skyboxes. It will attempt to use the BMP version if a TGA version is not present, but not all modern GPUs support this.<br>
Skybox textures must be encoded using the following settings
{| class="wikitable"
|-
! Format 
| TGA  || BMP
|-
! Resolution
| 256 x 256 || 256 x 256
|-
! Color depth 
| 24-bit (true color) || 8-bit (256 colors, no fewer)
|-
! Compression 
| Uncompressed or RLE compression || Uncompressed
|-
! Additional settings
| Image origin: Bottom-Left || Compatibility: No color space information
|}
Skybox textures must be put in {{code|$moddir\gfx\env\}}.
{{confirm|RLE-compressed TGA skyboxes work in OpenGL mode, but do they work in software mode?}}

== Creating a skybox for GoldSrc, using [[Source]] ==
It is possible to create an area of a Source map into a Skybox to be used in GoldSrc. Here's an simple example:
# Create a large outdoor area with some displacement maps and treelines, and fog to hide the edges. Lets call it ''' ''carrotjuice'' '''.
# Load the map ingame and turn cheats on ( ''sv_cheats 1'' ).
# Activate the noclip mode by simply opening the console and enter "'''noclip'''" and hit Enter.
# Fly to the center of where you want the skybox.
# Open up the console and type "'''mat_envmaptgasize 256'''", hit Enter.
# Now type "'''envmap'''" and press Enter. Now, 6 TGA files are now created and saved into a folder named "cubemap_screenshots" in your modfolder ( i.e. for Portal 2: ''Steam\SteamApps\common\Portal 2\portal2'' ).
Since the mapname was '' '''carrotjuice''' '', the name of the 6 TGA-files are as following:

 carrotjuicert.tga ''(Right)''
 carrotjuiceft.tga ''(Front)''
 carrotjuicelf.tga ''(Left)''
 carrotjuicebk.tga ''(Back)''
 carrotjuiceup.tga ''(Up)''
 carrotjuicedn.tga ''(Down)''

You can now copy or move these to your HL1-mods gfx\env-folder, to use it as skybox in a level.

== See also ==
* [[Skybox (2D)]]

== External links ==
* [http://the303.org/tutorials/gold_texture_p8.htm Custom Skies tutorial by The303]

[[Category:GoldSrc]]
[[Category:Glossary]]
[[Category:Skybox]]