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Creating env_cubemap_fog in older Source2 Games.

This guide explains how to create a functional env_cubemap_fog in older Source 2 games. This applies to Half-Life: Alyx iconHalf-Life: Alyx and Steam VR iconSteam VR.

warning

For Steam VR iconSteam VR, Method 1 is the way to go, since resourcecompiler has a bug where .vtex files, regardless of their settings, do not generate mipmaps, which are required for env_cubemap_fog to work properly.

Method 1​

info

If you change the texture in MaterialEditor, a new .vtex file will be generated, so you will need to set the new .vtex file again in the env_cubemap_fog entity in Hammer.

  1. Create your 2D skybox in MaterialEditor.
    met1

  2. Go to the AssetBrowser and search for your 2D skybox material. Right-click, then left-click on Asset Info, then left-click on Parent or Child assets, and copy the asset name.
    assetbrowsersrch
    assetbrowsersrch1
    assetbrowsersrch2

  3. Finally, copy the compiled asset name into the env_cubemap_fog entity in Hammer.
    hammercbmpfg1

Method 2​

  1. Create a .vtex file and set the
    "m_fileName" "string" "name_of_your_texture"
    to the relative path of your 2D skybox texture.
info

Your "m_outputFormat" "string" "compression_format" should always be BC7 (HDR block compression) or BC6H (high‑quality RGB or RGBA block compression), since skyboxes are normally 16‑bit or 32‑bit images.

<!-- dmx encoding keyvalues2_noids 1 format vtex 1 -->
"CDmeVtex"
{
    "m_inputTextureArray" "element_array" 
    [
        "CDmeInputTexture"
        {
            "m_name" "string" "InputTexture0"
            "m_fileName" "string" "materials/my_textures/my_texture.png"    // Replace this string
            "m_colorSpace" "string" "srgb"
            "m_typeString" "string" "2D"
            "m_imageProcessorArray" "element_array" 
            [
                "CDmeImageProcessor"
                {
                    "m_algorithm" "string" "None"
                    "m_stringArg" "string" ""
                    "m_vFloat4Arg" "vector4" "0 0 0 0"
                }
            ]
        }
    ]
    "m_outputTypeString" "string" "2D"
    "m_outputFormat" "string" "BC7"
    "m_outputClearColor" "vector4" "0 0 0 0"
    "m_nOutputMinDimension" "int" "0"
    "m_nOutputMaxDimension" "int" "0"
    "m_textureOutputChannelArray" "element_array" 
    [
        "CDmeTextureOutputChannel"
        {
            "m_inputTextureArray" "string_array" [ "InputTexture0" ]
            "m_srcChannels" "string" "rgba"
            "m_dstChannels" "string" "rgba"
            "m_mipAlgorithm" "CDmeImageProcessor"
            {
                "m_algorithm" "string" "Box"
                "m_stringArg" "string" ""
                "m_vFloat4Arg" "vector4" "0 0 0 0"
            }
            "m_outputColorSpace" "string" "srgb"
        }
    ]
    "m_vClamp" "vector3" "0 0 0"
    "m_bNoLod" "bool" "0"
}

  1. Compile your material. This is done automatically. If not, go to the Asset Browser, search for your texture, right‑click, and select Full Recompile.
    vtexcompile

  2. Finally, copy the compiled asset name into the env_cubemap_fog entity in Hammer.

Which method is better?​

It depends on your case. If your skybox has no modifications in MaterialEditor—such as brightness or exposure—then Method 2 is the better option, since it allows more control over the texture if you need to adjust lighting, resolution, etc.

Usually, you won’t need such tweaks, so Method 1 is recommended, and it is also more efficient since you only need one texture.

Preview in Hammer​

previewhammer