VTF (Valve Texture Format)

The Valve Texture Format (VTF) is the proprietary texture format used by the Source engine.

VTF files are just one layer in the Material System. VTFs ("Textures") can only be applied to Geometry via a VMT ("Material") File. VMTs can assign several VTFs to the same surface, and specify which Shader and Shader Parameters to use when rendering the textures.

VTF files can be compiled from TGA images using the Source SDK Tool Vtex, or a third-party VTF utility. VTFs and VMTs are stored in subfolders of the game_dir/materials directory.

To be valid, all textures must have dimensions that are powers of two (see the note about mipmaps under Storage capabilities below):

1
2
4
8
16
32
64
128
256
512
1024
2048
4096

Storage capabilities

The VTF image format can store either a Texture, an Environment Map, or a Volumetric Texture; and each of these may have multiple frames.

• An Environment Map may be a six faced cubemap or a (deprecated) single faced spheremap (v7.1 and up).

• For each frame and face, the VTF file contains both the basic original source-image data (pixel map) and a series of mipmaps used for rendering the texture over varying distances. Because each successive mipmap is exactly 1/2 the dimension (height and width) of the previous one, the source-image dimensions must be powers of 2. Although the source-image may be rectangular, square mipmaps are stored more efficiently in the VTF.

• VTF file data may also include several keyvalues:
  • the start frame for an animated VTF,
  • the bumpmap scale for the VTF,
  • the reflectivity vector of the VTF,
  • and a low resolution copy of the VTF (for color sampling by the engine).

Image data formats

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

Image data 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

A VTF file 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 NICE filtering 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.
• Addresses issues related to how gamma-correction is performed on textures for TV-output on XBOX 360 combined with hunting down OS Paged Pool Memory.

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.

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.

studiocompiler

includes VTF and VMT compile & decompile GUI.