2D Skybox

A 2D skybox is a skybox that lacks geometrical depth, consisting only of a skybox texture (without using the sky_camera entity to display a 3D miniature model).

A 2D skybox is a skybox that lacks geometrical depth, consisting only of a skybox texture (without using the sky_camera entity to display a 3D miniature model).

Adding sky to a map

Simply texture a world brush (not a brush entity) with the tools/toolsskybox or (if you are mapping for the Orange box) the tools/toolsskybox2d material.

In-game, the skybox will be seen through each surface that toolsskybox is applied to.

toolsskybox Brushes do not need to be box-shaped.

**Note:**In HL2 the default skybox has visible seams. This is not your fault. See the next section for how to change the default.

**Note:**You should avoid making a skybox by drawing a big hollowed out cube with the Skybox texture around your map.

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Changing the displayed skybox

See also Sky List

If you don't like the standard "sky_day01_01" sky, you can change it by setting the skybox name in Hammer's Map Properties dialog. With the correct map opened, follow these steps:

1. Go to the Map menu
2. Choose Map Properties... from the drop down list

3. In the Object Properties window, select the Skybox Texture Name field.

4. Replace the sky listed there with the name of the skybox you wish to display.

Skybox Lighting

Skybox Lighting enters the map through every toolsskybox-textured brush, representing direct sun/moonlight and diffuse skylight. Its basic properties are controlled by three entities used in combination (four in some games):

• light_environment defines the direction, color and intensity of the direct sunlight, and the color and intensity of the diffuse skylight.
• shadow_control defines the color, direction, and attenuation distance of the dynamic shadows that are created by light_environment. Dynamic shadows will be buggy and unconfigurable without this entity.
• env_sun places a glowing sprite in the skybox to represent the Sun's apparent position in the sky.
• env_cascade_light casts harsh, real-time shadows onto the map, usually copying settings from the light_environment. only.

To make sense of it all, just make sure you have only one of each of these entities in your map, and that the Pitch and Yaw <angles> are set the same for all three of them. (Pitch is equivalent to the Sun's angle of elevation from the ground, and Yaw is its compass bearing.)

These lighting settings - direction, color, brightness, etc are fairly specific to the actual image used for the 2D skybox. The Sky List article suggests some settings for official game skyboxes. The worldspawn entity defines which skybox to use. Also note that fog will look wrong if env_fog_controller's settings don't correspond to the particular skybox in use. Note:Pitch can be overriden for light_environment and env_sun, but not shadow_control. The Pitch override also cannot be switched off and its rotation is measured counter-clockwise from the horizontal (so straight down is -90°) whereas the **<angles> Pitch'**s rotation is clockwise (so straight down is +90°). The workaround for this is to make sure your Pitch override merely repeats the <angles> value; for example, if your shadow_control, light_environment and env_sun <angles> are "45 -60 0", set the Pitch override to "-45".

Creating a Custom 2D Skybox Texture

1. Prepare your image files. You need six images of the same resolution:

   • <skyname>BK

   • <skyname>DN

   • <skyname>FT

   • <skyname>LF

   • <skyname>RT

   • <skyname>UP

2. Convert them to VTF. Make sure that you enable "Clamp S" and "Clamp T" flags or you'll see seams when running with lower texture detail.
3. Create materials for each texture in \materials\skybox\, using the following template:

unlitgeneric
{
	$basetexture "<VTF>"
	$hdrcompressedtexture "<VTF>"
	$nofog 1
	$ignorez 1
}

Now, in Hammer, go to Map > Map Properties > Skybox Texture Name and type in your skybox name without any side tags.

Creating a 2D skybox for Goldsource, using Source

It is possible to create an area of your map into a 2D Skybox to be used in Goldsource (the HL1-engine). Here's an simple example:

1. Create a large outdoor area with some displacement maps and treelines, and fog to hide the edges. Lets call it carrotjuice .

2. Load the map ingame and turn cheats on ( sv_cheats 1 ).

3. Activate the noclip-mode by simply opening the console and enter "noclip" and hit Enter.

4. Fly to the center of where you want the skybox.

5. Open up the console and type "mat_envmaptgasize 256", hit Enter.

6. 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.

Source & reference

Source: https://developer.valvesoftware.com/wiki/Skybox_(2D)