D3D中的Alpha颜色混合（4）

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Each valid filter must contain exactly one of the following flags: D3DX_FILTER_NONE, D3DX_FILTER_POINT, D3DX_FILTER_LINEAR, D3DX_FILTER_TRIANGLE, or D3DX_FILTER_BOX. In addition, you can use the OR operator to specify zero or more of the following optional flags with a valid filter: D3DX_FILTER_MIRROR_U, D3DX_FILTER_MIRROR_V, D3DX_FILTER_MIRROR_W, D3DX_FILTER_MIRROR, D3DX_FILTER_DITHER, D3DX_FILTER_SRGB_IN, D3DX_FILTER_SRGB_OUT or D3DX_FILTER_SRGB.

Specifying D3DX_DEFAULT for this parameter is usually the equivalent of specifying D3DX_FILTER_TRIANGLE | D3DX_FILTER_DITHER. However, D3DX_DEFAULT can have different meanings, depending on which method uses the filter. For example:

• When using D3DXCreateTextureFromFileEx, D3DX_DEFAULT maps to D3DX_FILTER_TRIANGLE | D3DX_FILTER_DITHER.
• When using D3DXFilterTexture, D3DX_DEFAULT maps to D3DX_FILTER_BOX if the texture size is a power of two, and D3DX_FILTER_BOX | D3DX_FILTER_DITHER otherwise.

Reference each method to check for information about how D3DX_DEFAULT filter is mapped.

参数pSrcInfo的类型D3DXIMAGE_INFO详细说明：

Returns a description of the original contents of an image file.

typedef struct D3DXIMAGE_INFO {
    UINT Width;
    UINT Height;
    UINT Depth;
    UINT MipLevels;
    D3DFORMAT Format;
    D3DRESOURCETYPE ResourceType;
    D3DXIMAGE_FILEFORMAT ImageFileFormat;
} D3DXIMAGE_INFO, *LPD3DXIMAGE_INFO;

Members

Width

Width of original image in pixels.

Height

Height of original image in pixels.

Depth

Depth of original image in pixels.

MipLevels

Number of mip levels in original image.

Format

A value from the D3DFORMAT enumerated type that most closely describes the data in the original image.

ResourceType

Represents the type of the texture stored in the file. It is either D3DRTYPE_TEXTURE, D3DRTYPE_VOLUMETEXTURE, or D3DRTYPE_CubeTexture.

ImageFileFormat

Represents the format of the image file.

参数pPalette的类型PALETTEENTRY的详细说明：

Specifies the color and usage of an entry in a logical palette.

typedef struct PALETTEENTRY {
    BYTE peRed;
    BYTE peGreen;
    BYTE peBlue;
    BYTE peFlags;
} PALETTEENTRY, *LPPALETTEENTRY;

Members

peRed

The red intensity value for the palette entry.

peGreen

The green intensity value for the palette entry.

peBlue

The blue intensity value for the palette entry.

peFlags

The alpha intensity value for the palette entry. Note that as of DirectX 8, this member is treated differently than documented in the Platform SDK.

当背景色为透明黑色的纹理创建以后，就可以将该纹理对象所表示的图象透明地显示在其他图象的上面。

此时，需要设置渲染管道流水线的D3DRS_ALPHATESTENABLE状态值为TRUE，以开启Alpha测试。

D3DRS_ALPHATESTENABLE

TRUE to enable per pixel alpha testing. If the test passes, the pixel is processed by the frame buffer. Otherwise, all frame-buffer processing is skipped for the pixel.
The test is done by comparing the incoming alpha value with the reference alpha value, using the comparison function provided by the D3DRS_ALPHAFUNC render state. The reference alpha value is determined by the value set for D3DRS_ALPHAREF. For more information, see Alpha Testing State (Direct3D 9).

The default value of this parameter is FALSE.

// enable per pixel alpha testing
_d3d_device->SetRenderState(D3DRS_ALPHATESTENABLE, TRUE);

接着设置D3DRS_ALPHAREF的状态为一个0~255范围内的整数值。

// specifies a reference alpha value against which pixels are tested
_d3d_device->SetRenderState(D3DRS_ALPHAREF, 0x01);

再接着设置3DRS_ALPHAFUNC状态为D3DCMPFUNC的枚举值，决定测试将使用比较方式。

Defines the supported compare functions.

typedef enum D3DCMPFUNC
{
    D3DCMP_NEVER = 1,
    D3DCMP_LESS = 2,
    D3DCMP_EQUAL = 3,
    D3DCMP_LESSEQUAL = 4,
    D3DCMP_GREATER = 5,
    D3DCMP_NOTEQUAL = 6,
    D3DCMP_GREATEREQUAL = 7,
    D3DCMP_ALWAYS = 8,
    D3DCMP_FORCE_DWORD = 0x7fffffff,
} D3DCMPFUNC, *LPD3DCMPFUNC;

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Constants

D3DCMP_NEVER

Always fail the test.

D3DCMP_LESS

Accept the new pixel if its value is less than the value of the current pixel.

D3DCMP_EQUAL

Accept the new pixel if its value equals the value of the current pixel.

D3DCMP_LESSEQUAL

Accept the new pixel if its value is less than or equal to the value of the current pixel.

D3DCMP_GREATER

Accept the new pixel if its value is greater than the value of the current pixel.

D3DCMP_NOTEQUAL

Accept the new pixel if its value does not equal the value of the current pixel.

D3DCMP_GREATEREQUAL

Accept the new pixel if its value is greater than or equal to the value of the current pixel.

D3DCMP_ALWAYS

Always pass the test.

D3DCMP_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

The values in this enumerated type define the supported compare functions for the D3DRS_ZFUNC, D3DRS_ALPHAFUNC, and D3DRS_STENCILFUNC render states.

// Accept the new pixel if its value is greater than the value of the current pixel
_d3d_device->SetRenderState(D3DRS_ALPHAFUNC, D3DCMP_GREATEREQUAL);

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好了，该死的DirectX API 使用说明介绍终于可以结束了，来看一个具体的例子。

需要在工程中设置链接d3dx9.lib d3d9.lib dinput8.lib dxguid.lib。
由于文件中用到了GE_APP和GE_INPUT这两个类，它的具体使用说明请参阅 主窗口和DirectInput的封装。

若发现代码中存在错误，敬请指出。

源码及素材下载

来看看头文件TransparentBlend.h的定义：

/*************************************************************************************
[Include File]

PURPOSE:
Defines for Transparent blend.
*************************************************************************************/

#ifndef TRANSPARENT_BLEND_H
#define TRANSPARENT_BLEND_H

struct CUSTOM_VERTEX
{
float x, y, z, rhw;
float u, v;
};

#define CUSTOM_VERTEX_FVF (D3DFVF_XYZRHW | D3DFVF_TEX1)

class TRANSPARENT_BLEND
{
private:
IDirect3D9* _d3d;
IDirect3DDevice9* _d3d_device;
IDirect3DVertexBuffer9* _tiger_vertex_buffer;
IDirect3DVertexBuffer9* _gun_vertex_buffer;
IDirect3DTexture9* _tiger_texture;
IDirect3DTexture9* _gun_texture;

public:
float m_gun_pos_x, m_gun_pos_y;

public:
TRANSPARENT_BLEND();
~TRANSPARENT_BLEND();

bool Create_D3D_Device(HWND hwnd, bool full_screen = true);
bool Init_Tiger_Vertex_Buffer();
bool Init_Gun_Vertex_Buffer();
bool Create_All_Texture();
void Render();
void Release_COM_Object();
};

#endif

再来看看TransparentBlend.cpp的定义：

/*************************************************************************************
[Implement File]

PURPOSE:
Defines for Transparent blend.
*************************************************************************************/

#include "GE_COMMON.h"
#include "TransparentBlend.h"

//------------------------------------------------------------------------------------
// Constructor, initialize data.
//------------------------------------------------------------------------------------
TRANSPARENT_BLEND::TRANSPARENT_BLEND()
{
_d3d = NULL;
_d3d_device = NULL;
_tiger_vertex_buffer = NULL;
_gun_vertex_buffer = NULL;
_tiger_texture = NULL;
_gun_texture = NULL;

m_gun_pos_x = 500.0f;
m_gun_pos_y = 180.0f;
}

//------------------------------------------------------------------------------------
// Destructor, release COM object.
//------------------------------------------------------------------------------------
TRANSPARENT_BLEND::~TRANSPARENT_BLEND()
{
Release_COM_Object();
}