高级着色语言HLSL入门（2）

16.2 编译HLSL 着色器

16.2.1 常量表

每个着色器有一个常量表，用来保存它的变量。D3DX库通过ID3DXConstantTable接口，提供给应用程序访问着色器的常量表。通过这个接口我们能够在应用程序中设置着色器源代码中的变量。

我们现在描述ID3DXConstantTable接口的方法列表的实现，全部的列表请查阅Direct3D文档。

16.2.1.1 取得常量句柄

为了在应用程序中设置着色器中的一个特定变量，需要有一种方法去引用它，我们能够在应用程序中用D3DXHANDLE引用一个在着色器中的变量，下面的方法返回一个着色器中的变量的D3DXHANDLE，使用时，需要传递一个变量的名字作为参数：

D3DXHANDLE ID3DXConstantTable::GetConstantByName(

D3DXHANDLE hConstant, // scope of constant

LPCSTR pName // name of constant

);

Hconstant——我们要取得的父结构中变量句柄的D3DXHANDLE标识。例如，如果我们想获得一个特定数据结构中单一数据成员的句柄，我们可以传递结构实例的句柄。如果我们获得一个顶级变量的句柄，给这个参数设为NULL。

PName——我们想获得的句柄的着色器代码中的变量的名字。

Gets a constant by looking up its name.

D3DXHANDLE GetConstantByName(  D3DXHANDLE hConstant,  LPCSTR pName);

Parameters

hConstant

[in] Unique identifier to the parent data structure. If the constant is a top-level parameter (there is no parent data structure), use NULL.

pName

[in] Name of the constant.

Return Values

Returns a unique identifier to the constant.

例如，如果在着色器中变量的名字为ViewProjMatrix，并且这是顶级变量，我们这么写：

// 取得着色器中ViewProjMatrix变量的句柄

D3DXHANDLE h0;

h0 = ConstTable->GetConstantByName(0, "ViewProjMatrix");

16.2.1.2 设置常量

一旦应用程序有了一个D3DXHANDLE，要引用着色器代码中的具体变量，我们可以在应用程序中使用ID3DXConstantTable::SetXXX方法设置变量。如果我们想设置一个向量数组类型的变量，方法名是SetVectorArray。

ID3DXConstantTable::SetXXX的一般语法是：

HRESULT ID3DXConstantTable::SetXXX(

LPDIRECT3DDEVICE9 pDevice,

D3DXHANDLE hConstant,

XXX value

);

PDevice：常量表所关联的设备的指针。

HConstant：我们正在设置的变量句柄的引用。

Value：我们要把变量设置成的值，XXX是我们设置的要替换的变量类型名，对于有些类型（bool, int, float），传递变量值的COPY，另外一些类型（vectors, matrices, structures），传递值的指针。

下面的列表描述了我们能用ID3DXConstantTable接口设置的类型列表。这里假定我们有一个有效的设备，和一个有效句柄。

SetBool—Used to set a Boolean value. Sample call:

bool b = true;

ConstTable->SetBool(Device, handle, b);

Sets a Boolean value.

HRESULT SetBool(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  BOOL b);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the constant. See D3DXHANDLE.

[in] Boolean value.

Return Values

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

SetBoolArray—Used to set a Boolean array. Sample call:

bool b[3] = {true, false, true};

ConstTable->SetBoolArray(Device, handle, b, 3);

Sets an array of Boolean values.

HRESULT SetBoolArray(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  CONST BOOL* pB,  UINT Count);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the array of constants. See D3DXHANDLE.

[in] Array of Boolean values.

Count

[in] Number of Boolean values in the array.

Return Values

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

SetFloat—Used to set a float. Sample call:

float f = 3.14f;

ConstTable->SetFloat(Device, handle, f);

Sets a floating-point number.

HRESULT SetFloat(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  FLOAT f);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the constant. See D3DXHANDLE.

[in] Floating-point number.

Return Values

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

SetFloatArray—Used to set a float array. Sample call:

float f[2] = {1.0f, 2.0f};

ConstTable->SetFloatArray(Device, handle, f, 2);

Sets an array of floating-point numbers.

HRESULT SetFloatArray(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  CONST FLOAT* pf,  UINT Count);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the array of constants. See D3DXHANDLE.

[in] Array of floating-point numbers.

Count

[in] Number of floating-point values in the array.

Return Values

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

SetInt—Used to set an integer. Sample call:

int x = 4;

ConstTable->SetInt(Device, handle, x);

Sets an integer value.

HRESULT SetInt(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  INT n);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the constant. See D3DXHANDLE.

[in] Integer.

Return Values

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

SetMatrix—Used to set a 4 × 4 matrix. Sample call:

D3DXMATRIX M(…);

ConstTable->SetMatrix(Device, handle, &M);

Sets a nontransposed matrix.

HRESULT SetMatrix(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  CONST D3DXMATRIX* pMatrix);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the matrix of constants. See D3DXHANDLE.

pMatrix

[in] Pointer to a nontransposed matrix. See D3DXMATRIX.

Return Values

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

SetMatrixArray—Used to set a 4 × 4 matrix array. Sample call:

D3DXMATRIX M[4];

// ...Initialize matrices

ConstTable->SetMatrixArray(Device, handle, M, 4);

Sets an array of nontransposed matrices.

HRESULT SetMatrixArray(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  CONST D3DXMATRIX* pMatrix,  UINT Count);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to the array of constant matrices.

pMatrix

[in] Array of nontransposed matrices.

Count

[in] Number of matrices in the array.

Return Values

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

SetMatrixPointerArray—Used to set an array of 4 × 4 matrix pointers. Sample call:

D3DXMATRIX* M[4];

// ...Allocate and initialize matrix pointers

ConstTable->SetMatrixPointerArray(Device, handle, M, 4);

Sets an array of pointers to nontransposed matrices.

HRESULT SetMatrixPointerArray(  LPDIRECT3DDEVICE9 pDevice,  D3DXHANDLE hConstant,  CONST D3DXMATRIX ** ppMatrix,  UINT Count);

Parameters

pDevice

[in] Pointer to an IDirect3DDevice9 interface, representing the device associated with the constant table.

hConstant

[in] Unique identifier to an array of constant matrices.

ppMatrix

[in] Array of pointers to nontransposed matrices.

Count

[in] Number of matrices in the array.

Return Values

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

Remarks

A nontransposed matrix contains row-major data; that is, each vector is contained in a row.