对一些特殊的应用需要对纹理坐标进行处理，主要包括纹理坐标自动生成和纹理坐标变换。下图显示了纹理坐标的来源、处理过程以及到达光栅处理器的过程。

纹理坐标自动生成

在Direct3D程序中，不仅可以在模型载入阶段或渲染阶段指定物体的纹理坐标，还可以通过Direct3D渲染引擎自动生成纹理坐标，用于诸如环境映射等特殊的视觉效果。与手动设置纹理坐标相比，纹理坐标自动生成在Direct3D坐标 变换和光照流水线中完成，执行速度更快。

Direct3D系统可以使用经过变换的摄像机空间顶点位置坐标、法线信息来生成纹理坐标。如果使用纹理坐标自动生成，那么在顶点中就可以不用包含纹理坐标数据，从而可以降低图形渲染时的数据传输量。纹理坐标自动生成主要用于产生一些特殊效果，在大多数情况下还是手工为每个顶点指定纹理坐标。

通过调用SetTextureStageState()并将第二个参数设置为D3DTSS_TEXCOORDINDEX来控制Direct3D系统如何自动生成纹理坐标。

D3DTSS_TEXCOORDINDEX

Index of the texture coordinate set to use with this texture stage. You can specify up to eight sets of texture coordinates per vertex. If a vertex does not include a set of texture coordinates at the specified index, the system defaults to the u and v coordinates (0,0).

When rendering using vertex shaders, each stage's texture coordinate index must be set to its default value. The default index for each stage is equal to the stage index. Set this state to the zero-based index of the coordinate set for each vertex that this texture stage uses.

Additionally, applications can include, as logical OR with the index being set, one of the constants to request that Direct3D automatically generate the input texture coordinates for a texture transformation. For a list of all the constants, see D3DTSS_TCI.

With the exception of D3DTSS_TCI_PASSTHRU, which resolves to zero, if any of the following values is included with the index being set, the system uses the index strictly to determine texture wrapping mode. These flags are most useful when performing environment mapping.

其中第三个参数可以设为下列列表中的成员：

D3DTSS_TCI

Driver texture coordinate capability flags.

These constants are used by D3DTSS_TEXCOORDINDEX.

D3DTSS_TEXCOORDINDEX用于指定特定纹理层使用顶点中的第几组纹理坐标，但如果指定了上表中的成员值，Direct3D将忽略顶点中的纹理坐标，转而使用自动生成的纹理坐标。

D3DTSS_TEXTURETRANSFORMFLAGS用来控制生成的纹理坐标的输出，在大多数情况下纹理坐标是二维的，即将D3DTSS_TEXTURETRANSFORMFLAGS设置为D3DTTFF_COUNT2。但当绘制线段或三维纹理时，纹理坐标可能是一维或三维的。

D3DTSS_TEXTURETRANSFORMFLAGS

Member of the D3DTEXTURETRANSFORMFLAGS enumerated type that controls the transformation of texture coordinates for this texture stage. The default value is D3DTTFF_DISABLE.

输出的纹理坐标维数由枚举类型D3DTSS_TEXTURETRANSFORMFLAGS指定，其定义如下：

Defines texture coordinate transformation values.

typedef enum D3DTEXTURETRANSFORMFLAGS
{
    D3DTTFF_DISABLE = 0,
    D3DTTFF_COUNT1 = 1,
    D3DTTFF_COUNT2 = 2,
    D3DTTFF_COUNT3 = 3,
    D3DTTFF_COUNT4 = 4,
    D3DTTFF_PROJECTED = 256,
    D3DTTFF_FORCE_DWORD = 0x7fffffff,
} D3DTEXTURETRANSFORMFLAGS, *LPD3DTEXTURETRANSFORMFLAGS;

Constants

D3DTTFF_DISABLE

Texture coordinates are passed directly to the rasterizer.

D3DTTFF_COUNT1

The rasterizer should expect 1D texture coordinates. This value is used by fixed function vertex processing; it should be set to 0 when using a programmable vertex shader.

D3DTTFF_COUNT2

The rasterizer should expect 2D texture coordinates. This value is used by fixed function vertex processing; it should be set to 0 when using a programmable vertex shader.

D3DTTFF_COUNT3

The rasterizer should expect 3D texture coordinates. This value is used by fixed function vertex processing; it should be set to 0 when using a programmable vertex shader.

D3DTTFF_COUNT4

The rasterizer should expect 4D texture coordinates. This value is used by fixed function vertex processing; it should be set to 0 when using a programmable vertex shader.

D3DTTFF_PROJECTED

This flag is honored by the fixed function pixel pipeline, as well as the programmable pixel pipeline in versions ps_1_1 to ps_1_3. When texture projection is enabled for a texture stage, all four floating point values must be written to the corresponding texture register. Each texture coordinate is divided by the last element before being passed to the rasterizer. For example, if this flag is specified with the D3DTTFF_COUNT3 flag, the first and second texture coordinates are divided by the third coordinate before being passed to the rasterizer.

D3DTTFF_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

Texture coordinates can be transformed using a 4 x 4 matrix before the results are passed to the rasterizer. The texture coordinate transforms are set by calling IDirect3DDevice9::SetTextureStageState, and by passing in the D3DTSS_TEXTURETRANSFORMFLAGS texture stage state and one of the values from D3DTEXTURETRANSFORMFLAGS. For more information about texture transforms, see Texture Coordinate Transformations (Direct3D 9).

首先，我们定义顶点结构和格式：

struct sCustomVertex
{
	float x, y, z;
};

#define D3DFVF_CUSTOM_VERTEX	D3DFVF_XYZ

接着生成顶点数据，顶点数据中没有包含纹理坐标：

// create vertex buffer and fill data

sCustomVertex vertices[] = 	
{
    { -1.0f, -1.0f,  0.0f},
    { -1.0f,  1.0f,  0.0f},
    {  1.0f, -1.0f,  0.0f},
    {  1.0f,  1.0f,  0.0f}
};

pd3dDevice->CreateVertexBuffer(sizeof(vertices), 0, D3DFVF_CUSTOM_VERTEX, D3DPOOL_MANAGED, &g_vertex_buffer, NULL);

void* ptr;
g_vertex_buffer->Lock(0, sizeof(vertices), (void**)&ptr, 0);
memcpy(ptr, vertices, sizeof(vertices));
g_vertex_buffer->Unlock();

然后让Direct3D自动生成纹理坐标：

// create texture coordinate using vertex position in camera space 
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, D3DTSS_TCI_CAMERASPACEPOSITION);
pd3dDevice->SetTextureStageState(0, D3DTSS_TEXTURETRANSFORMFLAGS, D3DTTFF_COUNT2);

运行效果：

若设置D3DTSS_TEXCOORDINDEX为以下D3DTSS_TCI_CAMERASPACEREFLECTIONVECTOR，则效果为：

若设置D3DTSS_TEXCOORDINDEX为以下D3DTSS_TCI_SPHEREMAP，则效果为：

主程序：

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