Valve Texture Format

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The Valve Texture Format (VTF) is the proprietary texture format used by the Source engine. VTF files are generally referenced in a Material instead of being accessed directly, which allows re-use in different ways.

VTF files can be created from TGA images using the Source SDK Tool VTEX, or from most common image formats with third-party tools. Both textures and materials are stored in subfolders of game_dir/materials/.

Note:VTF files must have dimensions that are powers of two.

Storage capabilities

The VTF image format can store either a flat texture, an environment map, or a volumetric texture.Each of these can have multiple frames.

  • An environment map is a six-faced cube map
  • A volumetric texture is a texture with depth, where each frame is a "layer" which are layered in the third dimension. So a 16x16x16 volumetric texture has 16 separate 16x16 textures stacked to give depth. This format is used internally by Source, and you shouldn't have any need to actually create one yourself.
  • 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.
  • Start frame (for animations)
  • Bump map scale
  • A Reflectivity value for use by VRAD
  • A very low resolution copy of the VTF for color sampling by the engine.

Resources

VTF 7.3 added an extensible "resource data" system. Anything can be added, but Source will recognise only the following:

  • A CRC value, for detecting data corruption.
  • An U/V LOD control. This is the highest mipmap which should be loaded when game's Texture Detail setting is "High" (mat_picmip 0). An U LOD Control value of 11 selects the mipmap which is 2048 pixels (211) across.
    Note:Since users are currently only presented with one texture detail setting above High, there is little point setting this value to anything except 50% or 100% of your texture's size.
  • Animated particle sheet data.
  • Expanded texture settings. This is a collection of 32 flags, none of which are in use by Valve. Unlike the built-in VTF flags these can be defined on a game-by-game basis.

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 Comments
A8 0 0 0 8 8 False True
ABGR8888 8 8 8 8 32 False True Uncompressed texture with alpha
ARGB8888 8 8 8 8 32 False True
BGR565 5 6 5 0 16 False True Uncompressed texture, limited color depth
BGR888 8 8 8 0 24 False True Uncompressed texture
BGR888_BLUESCREEN 8 8 8 0 24 False True
BGRA4444 4 4 4 4 16 False True Uncompressed texture with alpha, half color depth
BGRA5551 5 5 5 1 16 False True
BGRA8888 8 8 8 8 32 Either True Also used for compressed HDR
BGRX5551 5 5 5 1 16 False True
BGRX8888 8 8 8 8 32 False True
DXT1 N/A N/A N/A 0 4 True True Standard compression, no alpha
DXT1_ONEBITALPHA N/A N/A N/A 1 4 True True Standard compression, one bit alpha
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 (recommended)
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 Integer 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 Uncompressed du/dv Format
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

HDR compression

HDR textures can be stored in compressed form using the BGRA8888 format.

The formula to convert these colors back to integer HDR is:

RGB = RGB * (A * 16)

and for floating point HDR:

RGB = (RGB * (A * 16)) / 262144

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). It can also be used to produce Very High quality textures.
  • 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.

Find technical details on the various DXT compression formats here.

Image flags

Tip:Most shader settings are configured as material parameters, not texture flags.

A VTF file can contain the following flags (version 7.5):

Flag Value Comment
Point Sampling 0x0001 Low quality, "pixel art" 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.
PWL Corrected 0x0040 Purpose unknown.
SRGB n/a Uses space RGB. Uself for High Gamuts. Deprecated in 7.5.
No Compress 0x0040 No DXT compression used. Depreciated
Normal Map 0x0080 Texture is a normal map.
No Mipmaps 0x0100 Render largest mipmap only. (Does not delete existing mipmaps, just disables them.)
No Level Of Detail 0x0200 Not affected by texture resolution settings.
No Minimum 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
Pre SRGB 0x80000 SRGB correction has already been applied
One Over Mipmap Level In Alpha 0x80000 Fill the alpha channel with 1/Mipmap Level. Depreciated (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 Do not buffer for Video Processing, generally render distance.
Nice Filtered 0x1000000 Use NICE filtering to generate mipmaps. (Internal to VTEX?)
Clamp U 0x2000000 Clamp U coordinates (for volumetric textures).
Vertex Texture 0x4000000 Usable as a vertex texture
SSBump 0x8000000 Texture is a SSBump. (SSB)
Border 0x20000000 Clamp to border colour on all texture coordinates

File format

The VTF image format is described as follows.

VTF layout

7.2 7.3 +
  1. VTF Header
  2. VTF Low Resolution Image Data
  3. 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
  1. VTF Header
  2. Resource entries
    • VTF Low Resolution Image Data
    • Other resource 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
{
	// Flags from the *.txt config file
	TEXTUREFLAGS_POINTSAMPLE = 0x00000001,
	TEXTUREFLAGS_TRILINEAR = 0x00000002,
	TEXTUREFLAGS_CLAMPS = 0x00000004,
	TEXTUREFLAGS_CLAMPT = 0x00000008,
	TEXTUREFLAGS_ANISOTROPIC = 0x00000010,
	TEXTUREFLAGS_HINT_DXT5 = 0x00000020,
	TEXTUREFLAGS_PWL_CORRECTED = 0x00000040,
	TEXTUREFLAGS_NORMAL = 0x00000080,
	TEXTUREFLAGS_NOMIP = 0x00000100,
	TEXTUREFLAGS_NOLOD = 0x00000200,
	TEXTUREFLAGS_ALL_MIPS = 0x00000400,
	TEXTUREFLAGS_PROCEDURAL = 0x00000800,
 
	// These are automatically generated by vtex from the texture data.
	TEXTUREFLAGS_ONEBITALPHA = 0x00001000,
	TEXTUREFLAGS_EIGHTBITALPHA = 0x00002000,
 
	// Newer flags from the *.txt config file
	TEXTUREFLAGS_ENVMAP = 0x00004000,
	TEXTUREFLAGS_RENDERTARGET = 0x00008000,
	TEXTUREFLAGS_DEPTHRENDERTARGET = 0x00010000,
	TEXTUREFLAGS_NODEBUGOVERRIDE = 0x00020000,
	TEXTUREFLAGS_SINGLECOPY	= 0x00040000,
	TEXTUREFLAGS_PRE_SRGB = 0x00080000,
 
        TEXTUREFLAGS_UNUSED_00100000 = 0x00100000,
	TEXTUREFLAGS_UNUSED_00200000 = 0x00200000,
	TEXTUREFLAGS_UNUSED_00400000 = 0x00400000,
 
	TEXTUREFLAGS_NODEPTHBUFFER = 0x00800000,
 
	TEXTUREFLAGS_UNUSED_01000000 = 0x01000000,
 
	TEXTUREFLAGS_CLAMPU = 0x02000000,
	TEXTUREFLAGS_VERTEXTEXTURE = 0x04000000,
	TEXTUREFLAGS_SSBUMP = 0x08000000,			
 
	TEXTUREFLAGS_UNUSED_10000000 = 0x10000000,
 
	TEXTUREFLAGS_BORDER = 0x20000000,
 
	TEXTUREFLAGS_UNUSED_40000000 = 0x40000000,
	TEXTUREFLAGS_UNUSED_80000000 = 0x80000000,
};

VTF header

typedef struct tagVTFHEADER
{
	char		signature[4];		// File signature ("VTF\0"). (or as little-endian integer, 0x00465456)
	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

v7.5

  • Released July 19th, 2010 as part of Alien Swarm
  • Bitwise equivalent to v7.4.
  • Redefines and revises two texture flags.
  • Spheremaps now officially redundant.
  • Most changes internal to the VTF creation process with VTEX, e.g. MipMap fading, Alpha decay and XBox360 formats.

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

Viewing
Windows thumbnail handler (Windows XP+)
VTF Explorer (Windows; can explore inside GCFs)
gdk-pixbuf-vtf (Gnome\Nautilus\Eog)
IrfanView plugin
Viewing & creating
VTFEdit (GUI) and VTFCmd (command line)
Photoshop Plug-in (6 and up)
GIMP Plug-in
Paint.NET Plug-in
3DSMax plugin (versions 6 to 2009)

See also

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