VTEX (Valve Texture)

VTEX is the proprietary texture format use by the Source 2 engine. The VTEX format includes a .vtex source file that describes how to compile the texture, and the actual compiled .vtex_c texture file.

For most uses the .vtex_c file is compiled automatically by the tools, and no .vtex source file is generated. In some cases, such as when creating sprites for particle effects, no automated tool exists and the .vtex file has to be created manually.

Source file format

The .vtex file is a DMX file usually created in the keyvalues2_noids text format. It describes how to compile a texture from a set of image inputs. Placing a .vtex file in the content directory of the current add-on will cause the tools to compile it when referenced.

Template file

<!-- 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"
			"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" "DXT1"
	"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"
}

File data format

Todo:  The lists are incomplete.

The .vtex file is structures as a CDmeVtex list with arrays for CDmeInputTexture input textures and CDmeTextureOutputChannel output channel sets.

CDmeVtex root keys

Attribute	Type	Description
m_inputTextureArray	element_array	Array of CDmeInputTexture entries describing each input image.
m_textureOutputChannelArray	element_array	Array of CDmeTextureOutputChannel entries describing sets of output channels.
m_outputTypeString	string	Type of texture to generate: 2D, 3D, CUBE, CUBEARRAY
m_outputFormat	string	Image data format to generate.
m_outputClearColor	vector4	Todo: Initial color before input textures are applied to the output.
m_nOutputMinDimension	int	The minimum size of a side of the output texture in pixels .
m_nOutputMaxDimension	int	The maximum size of a side of the output texture in pixels.
m_nOutputDimensionReduce	int	[Todo]
m_vClamp	vector3	Whether to clamp the S, T and U coordinates respectively.
m_bNoLod	bool	Disables Level of Detail.
m_bHiddenAssetFlag	bool	Marks the output file as a hidden asset.
m_bCreateLinearColorSpaceApiTexture	bool	[Todo]
m_nDisplayRectWidth	int	[Todo]
m_nDisplayRectHeight	int	[Todo]
m_nMotionVectorsMaxDistanceInPixels	int	[Todo]

CDmeInputTexture keys

Attribute	Type	Description
m_name	string	Name to refer to this input by.
m_fileName	string	Filename for the input image.
m_colorSpace	string	Image color space: linear or srgb
m_fileExt	string	[Todo]
m_nMinBitsPerChannel	int	[Todo]
m_typeString	string	Type of input texture: 2D, 3D, CUBE, CUBEARRAY
m_imageProcessorArray	element_array	Array of image processor algorithms to apply to the input.
m_bPassThroughToCompiledVtex	bool	Todo: Pass through the input image directly to the texture file?
m_n3DSliceCount	int	[Todo]
m_n3DSliceWidth	int	[Todo]
m_n3DSliceHeight	int	[Todo]

CDmeTextureOutputChannel keys

Attribute	Type	Description
m_srcChannels	string	Specifies the used channels of the input texture and their order: r, g, b and a
m_dstChannels	string	Specifies what channels of the output textures map to the specified input channels: r, g, b and a
m_mipAlgorithm	CDmeImageProcessor	Image processor algorithm to use for mipmap generation.
m_outputColorSpace	string	Output color space: linear or srgb
m_inputTextureArray	string_array	Array of input textures by their m_name keys.

CDmeImageProcessor keys

Attribute	Type	Description
m_algorithm	string	What algorithm to use for this image processor.
m_stringArg	string	Algorithm specific argument.
m_vFloat4Arg	vector4	Algorithm specific argument.

Image data formats

Format	Description
DXT1
DXT5
I8
RGBA8888
R16
RG1616
RGBA16161616
R16F
RG1616F
RGBA16161616F
R32F
RG3232F
RGB323232F
RGBA32323232F
BC6H
BC7
ATI2N
IA88
R11_EAC
RG11_EAC
ATI1N
BGRA8888

Image processor algorithms

These algorithms can be added to an input m_imageProcessorArray.

Algorithm	Description
None	Do nothing.
Inverse	Invert the image channels.
NormalizeNormals	Normalize the vectors of a normal map to have a length of 1.
FillToPowerOfTwo	Fill the texture to the nearest power of two size.
EncodeRGBM	Encode a HDR texture to RGBM: RGB with a multiplier in the alpha channel.

Mipmap processor algorithms

One of these algorithms can be selected as the mip processing algorithm for the output.

Algorithm	Description
None	Do nothing.
Box	Standard box filtered mipmaps
AlphaWeighted	Todo: Used for transparency masks and color in the same texture.
Normals	Todo: Normal maps?
HemiOctAnisoRoughness	Used with hemi-octahedron normal maps and anisotropic roughness maps packed into the RB and GA channels respectively.
HemiOctIsoRoughness_RG_B	Used with hemi-octahedron normal maps and regular isotropic roughness maps packed into the RB and G channels respectively.
GGXCubeMapBlur	Blur cubemap mips to use for variable roughness reflections with the GGX BRDF.
GGXCubeMapBlur_RGBM	Blur cubemap mips to use for variable roughness reflections with the GGX BRDF. For RGBM encoded textures.
RGBM	Generate mips for RGBM encoded textures.

Unknown processor algorithms

Todo: It is unknown if these algorithms work or if they can be invoked in any way.

Algorithm	Description
Brightness
GenerateSheetData

Compiled file format

^[Todo]

The compiled .vtex_c format can be extracted with the third party tool Valve Resource Viewer.