Sky (Source 1 shader)

Source Engine

Source 2

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Sky is a shader for materials in Source meant for 2D skyboxes. The old method of making skyboxes before Source 2007 involved using the UnlitGeneric shader with $ignorez 1. This shader expands the amount of usable parameters and also allows for HDR skyboxes.

Tip: (in all games since ) $basetexture is not necessary for games that are HDR-only, as only the $hdrbasetexture or $hdrcompressedtexture will be used.

Note: This shader always ignores fog. Skyboxes with UnlitGeneric (and without $nofog 1) are affected by fog.

Warning: The  Counter-Strike 2 import script doesn't like $hdrcompressedtexture; change it to $basetexture, then decompress to EXR with no_vtf and use that instead^[Clarify].

Warning: While rare, mat_fullbright set to 1 might sometimes break the rendering of this shader.

With an uncompressed HDR skybox texture

If the skybox texture uses uncompressed BGRA16f16f16f16f, then the VMT should look something like this:

sky
{
	$basetexture skybox/sky_wasteland_00up // Sky texture to use for LDR
	$hdrbasetexture skybox/sky_wasteland_00_hdrup // Uncompressed HDR Sky texture to use for HDR-enabled maps
	$nofog 1
	$ignorez 1
	$nomip 1
}

With a compressed HDR skybox texture

If the skybox has been compressed using BGRA8888, then $hdrcompressedtexture should be used instead:

sky
{
	$basetexture skybox/sky_wasteland_00up // Sky texture to use for LDR
	$hdrcompressedtexture skybox/sky_wasteland_00_hdrup // Compressed HDR Sky texture to use for HDR-enabled maps
	$nofog 1
	$ignorez 1
	$nomip 1
}

Todo: Figure out what the "HDR compression method B" mentioned in sky_hdr_dx9.cpp does differently, as it asks for $hdrcompressedtexture0, $hdrcompressedtexture1, and $hdrcompressedtexture2 instead of a single $hdrcompressedtexture.

Without an HDR skybox texture

If an HDR version of the skybox texture is not available, $hdrbasetexture can use the same VTF as $basetexture:

sky
{
	$basetexture skybox/sky_wasteland_00up // Sky texture to use for LDR
	$hdrbasetexture skybox/sky_wasteland_00up // Sky texture to use for HDR, if the texture has NOT been specifically compiled for HDR
	$nofog 1
	$ignorez 1
	$nomip 1
}

Issues

This article or section needs to be cleaned up to conform to a higher standard of quality because:

Reason 

See HDR Skybox Creation for better explanation of when $basetexturetransform may be necessary.

You might find that skyboxes sometimes fit the entire projection area of a level. To re-scale the material to fit, use $basetexturetransform or add the following line:

	$basetexturetransform "center 0 0 scale 1 2 rotate 0 translate 0 0" // For cutting off the bottom halves of the skybox

The scale 1 2 segment will maintain the fill-sizing of the X-axis, while locking the texture to the center line of the Y-axis (i.e. the absolute horizon line).