Creates a texture from a file.

HRESULT D3DXCreateTextureFromFile(
  LPDIRECT3DDEVICE9 pDevice,
  LPCTSTR pSrcFile,
  LPDIRECT3DTEXTURE9 * ppTexture
);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device to be associated with the texture.

pSrcFile

[in] Pointer to a string that specifies the filename. If the compiler settings require Unicode, the data type LPCTSTR resolves to LPCWSTR. Otherwise, the string data type resolves to LPCSTR. See Remarks.

ppTexture

[out] Address of a pointer to an IDirect3DTexture9 interface, representing the created texture object.

Return Values

If the function succeeds, the return value is D3D_OK. If the function fails, the return value can be one of the following:

Remarks

The compiler setting also determines the function version. If Unicode is defined, the function call resolves to D3DXCreateTextureFromFileW. Otherwise, the function call resolves to D3DXCreateTextureFromFileA because ANSI strings are being used.

This function supports the following file formats: .bmp, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga. See D3DXIMAGE_FILEFORMAT.

The function is equivalent to D3DXCreateTextureFromFileEx(pDevice, pSrcFile, D3DX_DEFAULT, D3DX_DEFAULT, D3DX_DEFAULT, 0, D3DFMT_UNKNOWN, D3DPOOL_MANAGED, D3DX_DEFAULT, D3DX_DEFAULT, 0, NULL, NULL, ppTexture).

Mipmapped textures automatically have each level filled with the loaded texture.

When loading images into mipmapped textures, some devices are unable to go to a 1x1 image and this function will fail. If this happens, the images need to be loaded manually.

Note that a resource created with this function will be placed in the memory class denoted by D3DPOOL_MANAGED.

Filtering is automatically applied to a texture created using this method. The filtering is equivalent to D3DX_FILTER_TRIANGLE | D3DX_FILTER_DITHER in D3DX_FILTER.

For the best performance when using D3DXCreateTextureFromFile:

1. Doing image scaling and format conversion at load time can be slow. Store images in the format and resolution they will be used. If the target hardware requires power of two dimensions, create and store images using power of two dimensions.
2. Consider using DirectDraw surface (DDS) files. Because DDS files can be used to represent any Direct3D 9 texture format, they are very easy for D3DX to read. Also, they can store mipmaps, so any mipmap-generation algorithms can be used to author the images.

可以使用更高級(jí)的函數(shù)D3DXCreateTextureFromFileEx來(lái)創(chuàng)建紋理對(duì)象。
 

Creates a texture from a file. This is a more advanced function than D3DXCreateTextureFromFile.

HRESULT D3DXCreateTextureFromFileEx(
  LPDIRECT3DDEVICE9 pDevice,
  LPCTSTR pSrcFile,
  UINT Width,
  UINT Height,
  UINT MipLevels,
  DWORD Usage,
  D3DFORMAT Format,
  D3DPOOL Pool,
  DWORD Filter,
  DWORD MipFilter,
  D3DCOLOR ColorKey,
  D3DXIMAGE_INFO * pSrcInfo,
  PALETTEENTRY * pPalette,
  LPDIRECT3DTEXTURE9 * ppTexture
);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device to be associated with the texture.

pSrcFile

[in] Pointer to a string that specifies the filename. If the compiler settings require Unicode, the data type LPCTSTR resolves to LPCWSTR. Otherwise, the string data type resolves to LPCSTR. See Remarks.

Width

[in] Width in pixels. If this value is zero or D3DX_DEFAULT, the dimensions are taken from the file and rounded up to a power of two. If the device supports non-power of 2 textures and D3DX_DEFAULT_NONPOW2 is specified, the size will not be rounded.

Height

[in] Height, in pixels. If this value is zero or D3DX_DEFAULT, the dimensions are taken from the file and rounded up to a power of two. If the device supports non-power of 2 textures and D3DX_DEFAULT_NONPOW2 is sepcified, the size will not be rounded.

MipLevels

[in] Number of mip levels requested. If this value is zero or D3DX_DEFAULT, a complete mipmap chain is created. If D3DX_FROM_FILE, the size will be taken exactly as it is in the file, and the call will fail if this violates device capabilities.

Usage

[in] 0, D3DUSAGE_RENDERTARGET, or D3DUSAGE_DYNAMIC. Setting this flag to D3DUSAGE_RENDERTARGET indicates that the surface is to be used as a render target. The resource can then be passed to the pNewRenderTarget parameter of the IDirect3DDevice9::SetRenderTarget method. If either D3DUSAGE_RENDERTARGET or D3DUSAGE_DYNAMIC is specified, Pool must be set to D3DPOOL_DEFAULT, and the application should check that the device supports this operation by calling IDirect3D9::CheckDeviceFormat. D3DUSAGE_DYNAMIC indicates that the surface should be handled dynamically. See Using Dynamic Textures.

Format

[in] Member of the D3DFORMAT enumerated type, describing the requested pixel format for the texture. The returned texture might have a different format from that specified by Format. Applications should check the format of the returned texture. If D3DFMT_UNKNOWN, the format is taken from the file. If D3DFMT_FROM_FILE, the format is taken exactly as it is in the file, and the call will fail if this violates device capabilities.

Pool

[in] Member of the D3DPOOL enumerated type, describing the memory class into which the texture should be placed.

Filter

[in] A combination of one or more D3DX_FILTER constants controlling how the image is filtered. Specifying D3DX_DEFAULT for this parameter is the equivalent of specifying D3DX_FILTER_TRIANGLE | D3DX_FILTER_DITHER.

MipFilter

[in] A combination of one or more D3DX_FILTER constants controlling how the image is filtered. Specifying D3DX_DEFAULT for this parameter is the equivalent of specifying D3DX_FILTER_BOX. In addition, use bits 27-31 to specify the number of mip levels to be skipped (from the top of the mipmap chain) when a .dds texture is loaded into memory; this allows you to skip up to 32 levels.

ColorKey

[in] D3DCOLOR value to replace with transparent black, or 0 to disable the color key. This is always a 32-bit ARGB color, independent of the source image format. Alpha is significant and should usually be set to FF for opaque color keys. Thus, for opaque black, the value would be equal to 0xFF000000.

pSrcInfo

[in, out] Pointer to a D3DXIMAGE_INFO structure to be filled in with a description of the data in the source image file, or NULL.

pPalette

[out] Pointer to a PALETTEENTRY structure, representing a 256-color palette to fill in, or NULL.

ppTexture

[out] Address of a pointer to an IDirect3DTexture9 interface, representing the created texture object.

Return Values

If the function succeeds, the return value is D3D_OK. If the function fails, the return value can be one of the following: D3DERR_INVALIDCALL.

Remarks

The compiler setting also determines the function version. If Unicode is defined, the function call resolves to D3DXCreateTextureFromFileExW. Otherwise, the function call resolves to D3DXCreateTextureFromFileExA because ANSI strings are being used.

Use D3DXCheckTextureRequirements to determine if your device can support the texture given the current state.

This function supports the following file formats: .bmp, .dds, .dib, .hdr, .jpg, .pfm, .png, .ppm, and .tga. See D3DXIMAGE_FILEFORMAT.

Mipmapped textures automatically have each level filled with the loaded texture. When loading images into mipmapped textures, some devices are unable to go to a 1x1 image and this function will fail. If this happens, then the images need to be loaded manually.

For the best performance when using D3DXCreateTextureFromFileEx:

1. Doing image scaling and format conversion at load time can be slow. Store images in the format and resolution they will be used. If the target hardware requires power of 2 dimensions, then create and store images using power of 2 dimensions.
2. For mipmap image creation at load time, filter using D3DX_FILTER_BOX. A box filter is much faster than other filter types such as D3DX_FILTER_TRIANGLE.
3. Consider using DDS files. Since DDS files can be used to represent any Direct3D 9 texture format, they are very easy for D3DX to read. Also, they can store mipmaps, so any mipmap-generation algorithms can be used to author the images.

When skipping mipmap levels while loading a .dds file, use the D3DX_SKIP_DDS_MIP_LEVELS macro to generate the MipFilter value. This macro takes the number of levels to skip and the filter type and returns the filter value, which would then be passed into the MipFilter parameter.
 

當(dāng)然也可以通過(guò)IDirect3DDevice9::CreateTexture來(lái)創(chuàng)建一個(gè)紋理對(duì)象。
 

Creates a texture resource.

HRESULT CreateTexture(
  UINT Width,
  UINT Height,
  UINT Levels,
  DWORD Usage,
  D3DFORMAT Format,
  D3DPOOL Pool,
  IDirect3DTexture9** ppTexture,
  HANDLE* pSharedHandle
);

Parameters

Width

[in] Width of the top-level of the texture, in pixels. The pixel dimensions of subsequent levels will be the truncated value of half of the previous level's pixel dimension (independently). Each dimension clamps at a size of 1 pixel. Thus, if the division by 2 results in 0, 1 will be taken instead.

Height

[in] Height of the top-level of the texture, in pixels. The pixel dimensions of subsequent levels will be the truncated value of half of the previous level's pixel dimension (independently). Each dimension clamps at a size of 1 pixel. Thus, if the division by 2 results in 0, 1 will be taken instead.

Levels

[in] Number of levels in the texture. If this is zero, Direct3D will generate all texture sublevels down to 1 by 1 pixels for hardware that supports mipmapped textures. Call IDirect3DBaseTexture9::GetLevelCount to see the number of levels generated.

Usage

[in] Usage can be 0, which indicates no usage value. However, if usage is desired, use a combination of one or more D3DUSAGE constants. It is good practice to match the usage parameter with the behavior flags in IDirect3D9::CreateDevice.

Format

[in] Member of the D3DFORMAT enumerated type, describing the format of all levels in the texture.

Pool

[in] Member of the D3DPOOL enumerated type, describing the memory class into which the texture should be placed.

ppTexture

[out, retval] Pointer to an IDirect3DTexture9 interface, representing the created texture resource.

pSharedHandle

[in] Reserved. Set this parameter to NULL.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be one of the following: D3DERR_INVALIDCALL, D3DERR_OUTOFVIDEOMEMORY, E_OUTOFMEMORY.

Remarks

An application can discover support for Automatic Generation of Mipmaps (Direct3D 9) in a particular format by calling IDirect3D9::CheckDeviceFormat with D3DUSAGE_AUTOGENMIPMAP. If IDirect3D9::CheckDeviceFormat returns D3DOK_NOAUTOGEN, IDirect3DDevice9::CreateTexture will succeed but it will return a one-level texture.

通過(guò)IDirect3DTexture9::LockRect創(chuàng)建完IDirect3DTexture9對(duì)象后，可以通過(guò)IDirect3DTexture9::LockRect獲得紋理數(shù)據(jù)。

Locks a rectangle on a texture resource.

HRESULT LockRect(
  UINT Level,
  D3DLOCKED_RECT * pLockedRect,
  CONST RECT * pRect,
  DWORD Flags
);

Parameters

Level

[in] Specifies the level of the texture resource to lock.

pLockedRect

[out] Pointer to a D3DLOCKED_RECT structure, describing the locked region.

pRect

[in] Pointer to a rectangle to lock. Specified by a pointer to a RECT structure. Specifying NULL for this parameter expands the dirty region to cover the entire texture.

Flags

[in] Combination of zero or more locking flags that describe the type of lock to perform. For this method, the valid flags are:

• D3DLOCK_DISCARD
• D3DLOCK_NO_DIRTY_UPDATE
• D3DLOCK_NOSYSLOCK
• D3DLOCK_READONLY

You may not specify a subrect when using D3DLOCK_DISCARD. For a description of the flags, see D3DLOCK.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.

Remarks

Textures created with D3DPOOL_DEFAULT are not lockable. Textures created in video memory are lockable when created with USAGE_DYNAMIC.

For performance reasons, dirty regions are recorded only for level zero of a texture. Dirty regions are automatically recorded when IDirect3DTexture9::LockRect is called without D3DLOCK_NO_DIRTY_UPDATE or D3DLOCK_READONLY. See IDirect3DDevice9::UpdateTexture for more information.

The only lockable format for a depth-stencil texture is D3DLOCK_D16_LOCKABLE.

Video memory textures cannot be locked, but must be modified by calling IDirect3DDevice9::UpdateSurface or IDirect3DDevice9::UpdateTexture. There are exceptions for some proprietary driver pixel formats that Direct3D 9 does not recognize. These can be locked.

This method cannot retrieve data from a texture resource created with D3DUSAGE_RENDERTARGET because such a texture must be assigned to D3DPOOL_DEFAULT memory and is therefore not lockable. In this case, use instead IDirect3DDevice9::GetRenderTargetData to copy texture data from device memory to system memory.

鎖定之后，必須通過(guò)IDirect3DTexture9::UnlockRect來(lái)對(duì)IDirect3DTexture9對(duì)象進(jìn)行解鎖。

Unlocks a rectangle on a texture resource.

HRESULT UnlockRect(
  UINT Level
);

Parameters

Level

[in] Specifies the level of the texture resource to unlock.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.

利用IDirect3DDevice9接口提供的SetTexture函數(shù)進(jìn)行紋理設(shè)置，由于可進(jìn)行多次紋理蒙皮，將紋理對(duì)象設(shè)置給固定渲染管道流水線時(shí)，必須提供所在的采樣器序號(hào)或紋理狀態(tài)序號(hào)，以區(qū)別不同的紋理處理。
 

Sets a texture.

HRESULT SetTexture(
  D3DXHANDLE hParameter,
  LPDIRECT3DBASETEXTURE9 pTexture
);

Parameters

hParameter

[in] Unique identifier. See Handles.

pTexture

[in] Texture object. See IDirect3DBaseTexture9.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.
 

可以通過(guò)GetLevelDesc來(lái)獲取特定采樣級(jí)別的紋理表面描述信息：
 

Retrieves a level description of a texture resource.

HRESULT GetLevelDesc(
  UINT Level,
  D3DSURFACE_DESC * pDesc
);

Parameters

Level

[in] Identifies a level of the texture resource. This method returns a surface description for the level specified by this parameter.

pDesc

[out] Pointer to a D3DSURFACE_DESC structure, describing the returned level.

Return Values

If the method succeeds, the return value is D3D_OK. D3DERR_INVALIDCALL is returned if one of the arguments is invalid.

pDesc為一個(gè)指向D3DSURFACE_DESC數(shù)據(jù)類(lèi)型的指針，來(lái)看看它的具體定義：
 

Describes a surface.

typedef struct D3DSURFACE_DESC {
    D3DFORMAT Format;
    D3DRESOURCETYPE Type;
    DWORD Usage;
    D3DPOOL Pool;
    D3DMULTISAMPLE_TYPE MultiSampleType;
    DWORD MultiSampleQuality;
    UINT Width;
    UINT Height;
} D3DSURFACE_DESC, *LPD3DSURFACE_DESC;

Members

Format

Member of the D3DFORMAT enumerated type, describing the surface format.

Type

Member of the D3DRESOURCETYPE enumerated type, identifying this resource as a surface.

Usage

Either the D3DUSAGE_DEPTHSTENCIL or D3DUSAGE_RENDERTARGET values. For more information, see D3DUSAGE.

Pool

Member of the D3DPOOL enumerated type, specifying the class of memory allocated for this surface.

MultiSampleType

Member of the D3DMULTISAMPLE_TYPE enumerated type, specifying the levels of full-scene multisampling supported by the surface.

MultiSampleQuality

Quality level. The valid range is between zero and one less than the level returned by pQualityLevels used by IDirect3D9::CheckDeviceMultiSampleType. Passing a larger value returns the error, D3DERR_INVALIDCALL. The MultisampleQuality values of paired render targets, depth stencil surfaces and the MultiSample type must all match.

Width

Width of the surface, in pixels.

Height

Height of the surface, in pixels.
 

Defines resource types.

typedef enum D3DRESOURCETYPE
{
    D3DRTYPE_SURFACE = 1,
    D3DRTYPE_VOLUME = 2,
    D3DRTYPE_TEXTURE = 3,
    D3DRTYPE_VOLUMETEXTURE = 4,
    D3DRTYPE_CubeTexture = 5,
    D3DRTYPE_VERTEXBUFFER = 6,
    D3DRTYPE_INDEXBUFFER = 7,
    D3DRTYPE_FORCE_DWORD = 0x7fffffff,
} D3DRESOURCETYPE, *LPD3DRESOURCETYPE;

Constants

D3DRTYPE_SURFACE

Surface resource.

D3DRTYPE_VOLUME

Volume resource.

D3DRTYPE_TEXTURE

Texture resource.

D3DRTYPE_VOLUMETEXTURE

Volume texture resource.

D3DRTYPE_CubeTexture

Cube texture resource.

D3DRTYPE_VERTEXBUFFER

Vertex buffer resource.

D3DRTYPE_INDEXBUFFER

Index buffer resource.

D3DRTYPE_FORCE_DWORD

Forces this enumeration to compile to 32 bits in size. Without this value, some compilers would allow this enumeration to compile to a size other than 32 bits. This value is not used.

Sets the sampler state value.

HRESULT SetSamplerState(
  DWORD Sampler,
  D3DSAMPLERSTATETYPE Type,
  DWORD Value
);

Parameters

Sampler

[in] The sampler stage index.

Type

[in] This parameter can be any member of the D3DSAMPLERSTATETYPE enumerated type.

Value

[in] State value to set. The meaning of this value is determined by the Type parameter.

Return Values

If the method succeeds, the return value is D3D_OK. If the method fails, the return value can be D3DERR_INVALIDCALL.

來(lái)看看D3DSAMPLERSTATETYPE的具體定義：

Sampler states define texture sampling operations such as texture addressing and texture filtering. Some sampler states set-up vertex processing, and some set-up pixel processing. Sampler states can be saved and restored using stateblocks (see State Blocks Save and Restore State (Direct3D 9)).

typedef enum D3DSAMPLERSTATETYPE
{
    D3DSAMP_ADDRESSU = 1,
    D3DSAMP_ADDRESSV = 2,
    D3DSAMP_ADDRESSW = 3,
    D3DSAMP_BORDERCOLOR = 4,
    D3DSAMP_MAGFILTER = 5,
    D3DSAMP_MINFILTER = 6,
    D3DSAMP_MIPFILTER = 7,
    D3DSAMP_MIPMAPLODBIAS = 8,
    D3DSAMP_MAXMIPLEVEL = 9,
    D3DSAMP_MAXANISOTROPY = 10,
    D3DSAMP_SRGBTEXTURE = 11,
    D3DSAMP_ELEMENTINDEX = 12,
    D3DSAMP_DMAPOFFSET = 13,
    D3DSAMP_FORCE_DWORD = 0x7fffffff,
} D3DSAMPLERSTATETYPE, *LPD3DSAMPLERSTATETYPE;

Constants

D3DSAMP_ADDRESSU

Texture-address mode for the u coordinate. The default is D3DTADDRESS_WRAP. For more information, see D3DTEXTUREADDRESS.

D3DSAMP_ADDRESSV

Texture-address mode for the v coordinate. The default is D3DTADDRESS_WRAP. For more information, see D3DTEXTUREADDRESS.

D3DSAMP_ADDRESSW

Texture-address mode for the w coordinate. The default is D3DTADDRESS_WRAP. For more information, see D3DTEXTUREADDRESS.

D3DSAMP_BORDERCOLOR

Border color or type D3DCOLOR. The default color is 0x00000000.

D3DSAMP_MAGFILTER

Magnification filter of type D3DTEXTUREFILTERTYPE. The default value is D3DTEXF_POINT.

D3DSAMP_MINFILTER

Minification filter of type D3DTEXTUREFILTERTYPE. The default value is D3DTEXF_POINT.

D3DSAMP_MIPFILTER

Mipmap filter to use during minification. See D3DTEXTUREFILTERTYPE. The default value is D3DTEXF_NONE.

D3DSAMP_MIPMAPLODBIAS

Mipmap level-of-detail bias. The default value is zero.

D3DSAMP_MAXMIPLEVEL

level-of-detail index of largest map to use. Values range from 0 to (n - 1) where 0 is the largest. The default value is zero.

D3DSAMP_MAXANISOTROPY

DWORD maximum anisotropy. The default value is 1.

D3DSAMP_SRGBTEXTURE

Gamma correction value. The default value is 0, which means gamma is 1.0 and no correction is required. Otherwise, this value means that the sampler should assume gamma of 2.2 on the content and convert it to linear (gamma 1.0) before presenting it to the pixel shader.

D3DSAMP_ELEMENTINDEX

When a multielement texture is assigned to the sampler, this indicates which element index to use. The default value is 0.

D3DSAMP_DMAPOFFSET

Vertex offset in the presampled displacement map. This is a constant used by the tessellator, its default value is 0.

D3DSAMP_FORCE_DWORD

Forces this enumeration to compile to 32 bits in size. Without this value, some compilers would allow this enumeration to compile to a size other than 32 bits. This value is not used.

對(duì)于過(guò)濾技術(shù)來(lái)說(shuō)，Type參數(shù)可取值D3DSAMP_MIPFILTER，D3DSAMP_MAGFILTER和 D3DSAMP_MINFILTER，而Value參數(shù)可取如下類(lèi)型的枚舉值。

Defines texture filtering modes for a texture stage.

typedef enum D3DTEXTUREFILTERTYPE
{
    D3DTEXF_NONE = 0,
    D3DTEXF_POINT = 1,
    D3DTEXF_LINEAR = 2,
    D3DTEXF_ANISOTROPIC = 3,
    D3DTEXF_PYRAMIDALQUAD = 6,
    D3DTEXF_GAUSSIANQUAD = 7,
    D3DTEXF_FORCE_DWORD = 0x7fffffff,
} D3DTEXTUREFILTERTYPE, *LPD3DTEXTUREFILTERTYPE;

Constants

D3DTEXF_NONE

Mipmapping disabled. The rasterizer should use the magnification filter instead.

D3DTEXF_POINT

Point filtering used as a texture magnification or minification filter. The texel with coordinates nearest to the desired pixel value is used. The texture filter to be used between mipmap levels is nearest-point mipmap filtering. The rasterizer uses the color from the texel of the nearest mipmap texture.

D3DTEXF_LINEAR

Bilinear interpolation filtering used as a texture magnification or minification filter. A weighted average of a 2 x 2 area of texels surrounding the desired pixel is used. The texture filter to use between mipmap levels is trilinear mipmap interpolation. The rasterizer linearly interpolates pixel color, using the texels of the two nearest mipmap textures.

D3DTEXF_ANISOTROPIC

Anisotropic texture filtering used as a texture magnification or minification filter. Compensates for distortion caused by the difference in angle between the texture polygon and the plane of the screen.

D3DTEXF_PYRAMIDALQUAD

A 4-sample tent filter used as a texture magnification or minification filter.

D3DTEXF_GAUSSIANQUAD

A 4-sample Gaussian filter used as a texture magnification or minification filter.

D3DTEXF_FORCE_DWORD

Forces this enumeration to compile to 32 bits in size. Without this value, some compilers would allow this enumeration to compile to a size other than 32 bits. This value is not used.

Remarks

To check if a format supports texture filter types other than D3DTEXF_POINT (which is always supported), call IDirect3D9::CheckDeviceFormat with D3DUSAGE_QUERY_FILTER.

Set a texture stage's magnification filter by calling IDirect3DDevice9::SetSamplerState with the D3DSAMP_MAGFILTER value as the second parameter and one member of this enumeration as the third parameter.

Set a texture stage's minification filter by calling IDirect3DDevice9::SetSamplerState with the D3DSAMP_MINFILTER value as the second parameter and one member of this enumeration as the third parameter.

Set the texture filter to use between-mipmap levels by calling IDirect3DDevice9::SetSamplerState with the D3DSAMP_MIPFILTER value as the second parameter and one member of this enumeration as the third parameter.

Not all valid filtering modes for a device will apply to volume maps. In general, D3DTEXF_POINT and D3DTEXF_LINEAR magnification filters will be supported for volume maps. If D3DPTEXTURECAPS_MIPVOLUMEMAP is set, then the D3DTEXF_POINT mipmap filter and D3DTEXF_POINT and D3DTEXF_LINEAR minification filters will be supported for volume maps. The device may or may not support the D3DTEXF_LINEAR mipmap filter for volume maps. Devices that support anisotropic filtering for 2D maps do not necessarily support anisotropic filtering for volume maps. However, applications that enable anisotropic filtering will receive the best available filtering (probably linear) if anisotropic filtering is not supported.

紋理地址模式

紋理源圖像的像素點(diǎn)都用紋理坐標(biāo)系的[0, 1] x [0, 1]范圍內(nèi)的坐標(biāo)來(lái)量度，如果選定的頂點(diǎn)紋理坐標(biāo)u和v大于1或小于0時(shí)，那么對(duì)應(yīng)的紋理像素點(diǎn)在紋理源圖上是不存在的。因此需要用相應(yīng)的紋理地址模式來(lái)尋址，確定該頂點(diǎn)顏色值應(yīng)該采用的紋理像素顏色值。由此可見(jiàn)，當(dāng)選定的待渲染三角形面頂點(diǎn)的紋理坐標(biāo)超出[0, 1]區(qū)間時(shí)，可獲得一些特別的渲染效果。

紋理地址模式具有包裝模式（Wrap），鏡像模式(Mirror)，夾子模式(Clamp)，邊界模式(Border)和一次鏡像模式(MirrorOnce)等多種尋址控制方式，來(lái)看看這些模式的枚舉定義：

Defines constants that describe the supported texture-addressing modes.

typedef enum D3DTEXTUREADDRESS
{
    D3DTADDRESS_WRAP = 1,
    D3DTADDRESS_MIRROR = 2,
    D3DTADDRESS_CLAMP = 3,
    D3DTADDRESS_BORDER = 4,
    D3DTADDRESS_MIRRORONCE = 5,
    D3DTADDRESS_FORCE_DWORD = 0x7fffffff,
} D3DTEXTUREADDRESS, *LPD3DTEXTUREADDRESS;

Constants

D3DTADDRESS_WRAP

Tile the texture at every integer junction. For example, for u values between 0 and 3, the texture is repeated three times; no mirroring is performed.

D3DTADDRESS_MIRROR

Similar to D3DTADDRESS_WRAP, except that the texture is flipped at every integer junction. For u values between 0 and 1, for example, the texture is addressed normally; between 1 and 2, the texture is flipped (mirrored); between 2 and 3, the texture is normal again; and so on.

D3DTADDRESS_CLAMP

Texture coordinates outside the range [0.0, 1.0] are set to the texture color at 0.0 or 1.0, respectively.

D3DTADDRESS_BORDER

Texture coordinates outside the range [0.0, 1.0] are set to the border color.

D3DTADDRESS_MIRRORONCE

Similar to D3DTADDRESS_MIRROR and D3DTADDRESS_CLAMP. Takes the absolute value of the texture coordinate (thus, mirroring around 0), and then clamps to the maximum value. The most common usage is for volume textures, where support for the full D3DTADDRESS_MIRRORONCE texture-addressing mode is not necessary, but the data is symmetric around the one axis.

D3DTADDRESS_FORCE_DWORD

Forces this enumeration to compile to 32 bits in size. Without this value, some compilers would allow this enumeration to compile to a size other than 32 bits. This value is not used.