Valve Texture Format

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Abstract

VTF (Valve Texture File) is proprietary texture format of the Source engine. These files contain not only the basic source data (colors, refraction, surface normals, etc.), but also mip-levels used for rendering the texture over varying distances.

Storing capabilities

The VTF image format can store single frame textures, multiple frame textures, single frame environment maps, multiple frame environment maps, single frame volumetric textures and multiple frame volumetric textures.

Environment maps consist of a six face cubemap and optional (deprecated) single face spheremap (v7.1 and up).

For each frame and face, additional mipmaps, a collection of several automatically generated variants of the original texture, are also stored.

Additional data contained within the VTF image format includes several flags, the start frame for animated VTFs, the bump map scale for the VTF, the reflectivity vector of the VTF and a low resolution copy of the VTF (for color sampling by the engine).

Hierarchy within the material system

Valve Texture Files are just one part of the Material System.

They are created from targa (.tga) images, and in turn referred to in Valve Materials, which can consist of several of these.

Image formats

The VTF image format can store image data in a variety of formats. Some formats were meant for the engine, some as an intermittent format for conversions. The uncompressed formats are not lossy and the compressed (DXT) formats are.

Image format table

Format Red Bits Green Bits Blue Bits Alpha Bits Total Bits Compressed Supported Comment
A8 0 0 0 8 8 False True
ABGR8888 8 8 8 8 32 False True
ARGB8888 8 8 8 8 32 False True
BGR565 5 6 5 0 16 False True
BGR888 8 8 8 0 24 False True
BGR888_BLUESCREEN 8 8 8 0 24 False True
BGRA4444 4 4 4 4 16 False True
BGRA5551 5 5 5 1 16 False True
BGRA8888 8 8 8 8 32 False True
BGRX5551 5 5 5 0 16 False True
BGRX8888 8 8 8 0 32 False True
DXT1 N/A N/A N/A 0 4 True True
DXT1_ONEBITALPHA N/A N/A N/A 1 4 True True
DXT3 N/A N/A N/A 4 8 True True Uninterpolated Alpha
DXT5 N/A N/A N/A 4 8 True True Interpolated Alpha
I8 N/A N/A N/A N/A 8 False True Luminance (Grayscale)
IA88 N/A N/A N/A 8 16 False True Luminance (Grayscale)
P8 N/A N/A N/A N/A 8 False False Paletted
RGB565 5 6 5 0 16 False True
RGB888 8 8 8 0 24 False True
RGB888_BLUESCREEN 8 8 8 0 24 False True
RGBA16161616 16 16 16 16 64 False True HDR Format
RGBA16161616F 16 16 16 16 64 False True Floating Point HDR Format
RGBA8888 8 8 8 8 32 False True
UV88 N/A N/A N/A N/A 16 False True
UVLX8888 N/A N/A N/A N/A 32 False True
UVWQ8888 N/A N/A N/A N/A 32 False True
Comparison of how DXTn compression affects different types of images

Choosing an image format

Though the VTF image format provides support for a wide range of image data formats, there are only a handful of image data formats you are likely to use. These formats and their criteria are described below:

  • BGR888: use this format for textures with no alpha channel and very fine gradients (i.e. normal maps or light halos).
  • BGRA8888: use this format for textures with an alpha channel and very fine gradients (i.e. normal maps or light halos).
  • DXT1: use this format for typical textures with no alpha channel.
  • DXT3: use this format for typical textures with an alpha channel with sharp gradients.
  • DXT5: use this format for typical textures with an alpha channel with smooth gradients.
  • I8: use this format for black and white textures with no alpha channel and very fine gradients (i.e. light halos).
  • IA88: use this format for black and white textures with an alpha channel and very fine gradients (i.e. smoke or light halos).
  • RGBA16161616F: use this format for HDR textures.
  • UV88: use this format for DuDv maps.

Image flags

The VTF image format can contain the following flags:

Flag Value Comment
Point Sampling 0x0001 Low quality texture filtering.
Trilinear Sampling 0x0002 Medium quality texture filtering.
Clamp S 0x0004 Clamp S coordinates.
Clamp T 0x0008 Clamp T coordinates.
Anisotropic Sampling 0x0010 High quality texture filtering.
Hint DXT5 0x0020 Used in skyboxes. Makes sure edges are seamless.
No Compress 0x0040 No DXT compression used.
NORMAL 0x0080 Texture is a normal map.
No Mipmaps 0x0100 Render largest mipmap only.
No LOD 0x0200 Use largest mipmap set, even on old hardware.
Min Mipmap 0x0400
Procedural 0x0800 Texture is an procedural texture (code can modify it).
One Bit Alpha 0x1000 One bit alpha channel used.
Eight Bit Alpha 0x2000 Eight bit alpha channel used.
Environment Map 0x4000 Texture is an environment map.
Render Target 0x8000 Texture is a render target.
Depth Render Target 0x10000 Texture is a depth render target.
No Debug Override 0x20000
Single Copy 0x40000
One Over Mipmap Level In Alpha 0x80000 Fill the alpha channel with 1/Mipmap Level. (Internal to VTEX?)
Premultiply Color By One Over Mipmap Level 0x100000 (Internal to VTEX?)
Normal To DuDv 0x200000 Texture is a DuDv map. (Internal to VTEX?)
Alpha Test Mipmap Generation 0x400000 (Internal to VTEX?)
No Depth Buffer 0x800000
Nice Filtered 0x1000000 Use the nice filter to generate mipmaps. (Internal to VTEX?)
Clamp U 0x2000000 Clamp U coordinates (for volumetric textures).

File format

The VTF image format is described as follows.

VTF layout

VTF Header
VTF Low Resolution Image Data
For Each Mipmap (Smallest to Largest)
  For Each Frame (First to Last)
    For Each Face (First to Last)
      For Each Z Slice (Min to Max; Varies with Mipmap)
        VTF High Resolution Image Data

VTF enumerations

enum
{
	IMAGE_FORMAT_NONE = -1,
	IMAGE_FORMAT_RGBA8888 = 0,
	IMAGE_FORMAT_ABGR8888,
	IMAGE_FORMAT_RGB888,
	IMAGE_FORMAT_BGR888,
	IMAGE_FORMAT_RGB565,
	IMAGE_FORMAT_I8,
	IMAGE_FORMAT_IA88,
	IMAGE_FORMAT_P8,
	IMAGE_FORMAT_A8,
	IMAGE_FORMAT_RGB888_BLUESCREEN,
	IMAGE_FORMAT_BGR888_BLUESCREEN,
	IMAGE_FORMAT_ARGB8888,
	IMAGE_FORMAT_BGRA8888,
	IMAGE_FORMAT_DXT1,
	IMAGE_FORMAT_DXT3,
	IMAGE_FORMAT_DXT5,
	IMAGE_FORMAT_BGRX8888,
	IMAGE_FORMAT_BGR565,
	IMAGE_FORMAT_BGRX5551,
	IMAGE_FORMAT_BGRA4444,
	IMAGE_FORMAT_DXT1_ONEBITALPHA,
	IMAGE_FORMAT_BGRA5551,
	IMAGE_FORMAT_UV88,
	IMAGE_FORMAT_UVWQ8888,
	IMAGE_FORMAT_RGBA16161616F,
	IMAGE_FORMAT_RGBA16161616,
	IMAGE_FORMAT_UVLX8888
};
enum
{
	TEXTUREFLAGS_POINTSAMPLE = 0x00000001,
	TEXTUREFLAGS_TRILINEAR = 0x00000002,
	TEXTUREFLAGS_CLAMPS = 0x00000004,
	TEXTUREFLAGS_CLAMPT = 0x00000008,
	TEXTUREFLAGS_ANISOTROPIC = 0x00000010,
	TEXTUREFLAGS_HINT_DXT5 = 0x00000020,
	TEXTUREFLAGS_NOCOMPRESS = 0x00000040,
	TEXTUREFLAGS_NORMAL = 0x00000080,
	TEXTUREFLAGS_NOMIP = 0x00000100,
	TEXTUREFLAGS_NOLOD = 0x00000200,
	TEXTUREFLAGS_MINMIP = 0x00000400,
	TEXTUREFLAGS_PROCEDURAL = 0x00000800,
	TEXTUREFLAGS_ONEBITALPHA = 0x00001000,
	TEXTUREFLAGS_EIGHTBITALPHA = 0x00002000,
	TEXTUREFLAGS_ENVMAP = 0x00004000,
	TEXTUREFLAGS_RENDERTARGET = 0x00008000,
	TEXTUREFLAGS_DEPTHRENDERTARGET = 0x00010000,
	TEXTUREFLAGS_NODEBUGOVERRIDE = 0x00020000,
	TEXTUREFLAGS_SINGLECOPY = 0x00040000,
	TEXTUREFLAGS_ONEOVERMIPLEVELINALPHA = 0x00080000,
	TEXTUREFLAGS_PREMULTCOLORBYONEOVERMIPLEVEL = 0x00100000,
	TEXTUREFLAGS_NORMALTODUDV = 0x00200000,
	TEXTUREFLAGS_ALPHATESTMIPGENERATION = 0x00400000,
	TEXTUREFLAGS_NODEPTHBUFFER = 0x00800000,
	TEXTUREFLAGS_NICEFILTERED = 0x01000000,
	TEXTUREFLAGS_CLAMPU = 0x02000000
};

VTF header

typedef struct tagVTFHEADER
{
	char		signature[4];		// File signature ("VTF\0").
	unsigned int	version[2];		// version[0].version[1] (currently 7.2).
	unsigned int	headerSize;		// Size of the header struct (16 byte aligned; currently 80 bytes).
	unsigned short	width;			// Width of the largest mipmap in pixels. Must be a power of 2.
	unsigned short	height;			// Height of the largest mipmap in pixels. Must be a power of 2.
	unsigned int	flags;			// VTF flags.
	unsigned short	frames;			// Number of frames, if animated (1 for no animation).
	unsigned short	firstFrame;		// First frame in animation (0 based).
	unsigned char	padding0[4];		// reflectivity padding (16 byte alignment).
	float		reflectivity[3];	// reflectivity vector.
	unsigned char	padding1[4];		// reflectivity padding (8 byte packing).
	float		bumpmapScale;		// Bumpmap scale.
	unsigned int	highResImageFormat;	// High resolution image format.
	unsigned char	mipmapCount;		// Number of mipmaps.
	unsigned int	lowResImageFormat;	// Low resolution image format (always DXT1).
	unsigned char	lowResImageWidth;	// Low resolution image width.
	unsigned char	lowResImageHeight;	// Low resolution image height.
	unsigned short	depth;			// Depth of the largest mipmap in pixels. Must be a power of 2.  Can be 0 or 1 for a 2D texture.  v7.2 only.
} VTFHEADER;

VTF lo-res image data

Tightly packed low resolution image data in the format described in the header. The low resolution image data is always stored in the DXT1 compressed image format. Its dimensions are that of the largest mipmap with a width or height that does not exceed 16 pixels. i.e. for a 256x256 pixel VTF: 16x16, for a 256x64 pixel VTF: 16x4, for a 1x32 pixel VTF: 1x16, for a 4x4 pixel VTF: 4x4.

VTF hi-res image data

Tightly packed interleaved high resolution image data in the format described in the header. Common image formats include DXT1, DXT5, BGR888, BGRA8888 and UV88. All dimensions must be a power of two.

Version history

v7.4

  • Released October 10th, 2007 as part of The Orange Box.
  • Bitwise equivalent to v7.3.

v7.3

  • Added an extensible resource orientated structure.
  • Added CRC, Texture LOD Control and Sheet resources, along with backwards compatible Image and Low Resolution Image resources.
  • Added several vendor specific depth-stencil formats (for internal engine use), along with normal map formats and linear uncompressed formats.
  • Released September 18th, 2007 as part of the Team Fortress 2 beta.

v7.2

  • Added volumetric texture support.
  • Released September 23rd, 2005 as a Steam engine update.

v7.1

  • Added spheremap support to environment maps. (This was intended for DirectX 6 support which was later cut.)

v7.0

  • Initial release. (Internal release only, however, some v7.0 textures made it to the published title.)

Implementation

An example Steam independent implementation of the VTF image file format can be found in the LGPL C/C++ library VTFLib.

Utilities

3DSMax VTF plugin
3D Studio Max 6/7/8 VTF Plug-in.
IrfanView
General purpose image viewer with optional VTF support (see PlugIns section).
Leadwerks Image Viewer
General purpose image viewer with VTF support.
Paint.NET Plug-in
Paint.NET VTF Plug-in.
Photoshop Plug-in
Photoshop 6 (and up) VTF Plug-in.
Shell Extension
Windows XP/2000 VTF shell extension.
VTFTool
Windows based VTEX and VTF2TGA replacement.
vmtCreate
VTEX frontend GUI.
VTFCmd
VTF and VMT command line editing tool (VTEX clone).
VTFEdit
VTF and VMT viewer and editing GUI.
VTF Explorer
VTF and VMT viewer\explorer GUI. Easy and extensible VMT creation. Can browse GCF files.