Valve Texture File: Difference between revisions

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== Abstract ==
#REDIRECT [[VTF]]
Source's proprietary texture format. 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 regardless of whether they are used by the Engine.
 
Additional data contained within the VTF image format includes several flags, the start frame for animated VTFs, 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).
 
VTF files are just one part of the [[:Category:Material System|Material System]], a [[VMT]] file (and possibly other VTF files) are also needed to complete the material.
 
== 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 ||
|}
 
[[Image:Dxtn_comparison.jpg|right|100px|thumb|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 ||
|-
| 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 ||
|-
| Premultiply Color By One Over Mipmap Level  || 0x100000 ||
|-
| Normal To DuDv  || 0x200000 || Texture is a DuDv map.
|-
| Alpha Test Mipmap Generation  || 0x400000 ||
|-
| No Depth Buffer  || 0x800000 ||
|-
| Nice Filtered  || 0x1000000 ||
|-
| 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 Low Resolution 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 High Resolution 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 2.
 
=== Version History ===
 
'''v7.2'''
* Added volumetric texture support. (September 23rd, 2005 [[Steam]] 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 | 3DSMax VTF plugin]]:3D Studio Max 6/7 VTF Plug-in.
;[http://nemesis.thewavelength.net/index.php?p=39 Photoshop Plug-in]:Photoshop 6 (and up) VTF Plug-in.
;[[VTF_Shell_Extensions | Shell Extension]]:Windows XP/2000 VTF shell extension.
;[[VTFTool]]:Windows based VTEX and VTF2TGA replacement.
;[http://www.electrofiction.com/ vmtCreate]:VTEX frontend GUI.
;[[VTFCmd]]:VTF and VMT command line editing tool (VTEX clone).
;[[VTFEdit]]:VTF and VMT viewer and editing GUI.
;[http://www.hl2source.com/?content=projects&id=vtftool VTF Explorer]:VTF viewer GUI.
 
 
[[category:Glossary]]
[[category:Material_System]]

Revision as of 06:14, 11 October 2005

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