D3D中的Alpha颜色混合（1）

提示：

阅读本文需要一定的3D图形学和DirectX9基础，如果你发现阅读困难，请参阅D3D中的材质和光照处理 。
本文用到的坐标系统变换函数请参阅DirectX 9的坐标系统变换。

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渲染管道流水线通常需要将来自顶点的颜色，纹理像素的颜色，光照颜色以及物体表面材质反射光颜色进行混合，生成计算机屏幕的像素颜色。将多种颜色混合在一起，必须考虑各种颜色的成分比例，这个比例由Alpha因子决定。对于游戏开发来说，利用Alpha颜色混合可产生背景透明的渲染效果。

颜色混合原理

一般的，屏幕像素的当前颜色值SrcColor可与目标像素颜色值DestColor进行如下运算，然后将获得的颜色值Color作为该像素的新颜色，以实现像素的目标颜色与源颜色的混合。

Color = SrcColor * SrcBlend + DestColor * DestBlend

这里，SrcBlend和DestBlend为源混合因子和目标混合因子，分别乘以源颜色和目标颜色。SrcColor ，SrcBlend ， DestColor ，DestBlend都是一个4维向量，而乘法运算 * 则是一个一个向量点积运算。

假设4维向量SrcColor=(Rs, Gs, Bs, As)，SrcBlend=(S1, S2, S3, S4), DestColor=(Rd, Gd, Bd, Ad)，DestBlend(D1, D2, D3, D4)，则混合颜色Color可用4维向量表示为：

Color = (Rs * S1 + Rd * D1, Gs * S2 + Gd * D2, Bs * S3 + Bd * D3, As * S4 + Ad * D4)

利用Direct3D设备接口提供的SetRenderState函数可将所要使用的混合因子设置给渲染管道流水线。此时，函数的第一个参数必须指定为D3DRS_SRCBLEND或D3DRS_DESTBLEND，分别表示设置源混合因子和目标混合因子，如下所示：
 

// IDirect3DDevice9* _d3d_device;

// set alpha blend for source color
 _d3d_device->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);

 // set alpha blend for dest color
  _d3d_device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

D3DBLEND_SRCALPHA和D3DBLEND_INVSRCALPHA均为DirectX预定义的混合因子宏，来看看具体定义：

Defines the supported blend mode.

typedef enum D3DBLEND
{
    D3DBLEND_ZERO = 1,
    D3DBLEND_ONE = 2,
    D3DBLEND_SRCCOLOR = 3,
    D3DBLEND_INVSRCCOLOR = 4,
    D3DBLEND_SRCALPHA = 5,
    D3DBLEND_INVSRCALPHA = 6,
    D3DBLEND_DESTALPHA = 7,
    D3DBLEND_INVDESTALPHA = 8,
    D3DBLEND_DESTCOLOR = 9,
    D3DBLEND_INVDESTCOLOR = 10,
    D3DBLEND_SRCALPHASAT = 11,
    D3DBLEND_BOTHSRCALPHA = 12,
    D3DBLEND_BOTHINVSRCALPHA = 13,
    D3DBLEND_BLENDFACTOR = 14,
    D3DBLEND_INVBLENDFACTOR = 15,
    D3DBLEND_FORCE_DWORD = 0x7fffffff,
} D3DBLEND, *LPD3DBLEND;

Constants

D3DBLEND_ZERO

Blend factor is (0, 0, 0, 0).

D3DBLEND_ONE

Blend factor is (1, 1, 1, 1).

D3DBLEND_SRCCOLOR

Blend factor is (R_s, G_s, B_s, A_s).

D3DBLEND_INVSRCCOLOR

Blend factor is (1 - R_s, 1 - G_s, 1 - B_s, 1 - A_s).

D3DBLEND_SRCALPHA

Blend factor is (A_s, A_s, A_s, A_s).

D3DBLEND_INVSRCALPHA

Blend factor is ( 1 - A_s, 1 - A_s, 1 - A_s, 1 - A_s).

D3DBLEND_DESTALPHA

Blend factor is (A_d A_d A_d A_d).

D3DBLEND_INVDESTALPHA

Blend factor is (1 - A_d 1 - A_d 1 - A_d 1 - A_d).

D3DBLEND_DESTCOLOR

Blend factor is (R_d, G_d, B_d, A_d).

D3DBLEND_INVDESTCOLOR

Blend factor is (1 - R_d, 1 - G_d, 1 - B_d, 1 - A_d).

D3DBLEND_SRCALPHASAT

Blend factor is (f, f, f, 1); where f = min(A_s, 1 - A_d).

D3DBLEND_BOTHSRCALPHA

Obsolete. Starting with DirectX 6, you can achieve the same effect by setting the source and destination blend factors to D3DBLEND_SRCALPHA and D3DBLEND_INVSRCALPHA in separate calls.

D3DBLEND_BOTHINVSRCALPHA

Source blend factor is (1 - A_s, 1 - A_s, 1 - A_s, 1 - A_s), and destination blend factor is (A_s, A_s, A_s, A_s); the destination blend selection is overridden. This blend mode is supported only for the D3DRS_SRCBLEND render state.

D3DBLEND_BLENDFACTOR

Constant color blending factor used by the frame-buffer blender. This blend mode is supported only if D3DPBLENDCAPS_BLENDFACTOR is set in the SrcBlendCaps or DestBlendCaps members of D3DCAPS9.

D3DBLEND_INVBLENDFACTOR

Inverted constant color-blending factor used by the frame-buffer blender. This blend mode is supported only if the D3DPBLENDCAPS_BLENDFACTOR bit is set in the SrcBlendCaps or DestBlendCaps members of D3DCAPS9.

D3DBLEND_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

In the preceding member descriptions, the RGBA values of the source and destination are indicated by the s and d subscripts.

The values in this enumerated type are used by the following render states:

• D3DRS_DESTBLEND
• D3DRS_SRCBLEND
• D3DRS_DESTBLENDALPHA
• D3DRS_SRCBLENDALPHA

由于渲染管道流水线的默认Alpha颜色混合功能是禁用的，因此必须调用SetRenderState函数设置D3DRS_ALPHABLENDENABLE为true.
 

// enable alpha-blended transparency
_d3d_device->SetRenderState(D3DRS_ALPHABLENDENABLE, true);

 

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来看一个具体的例子：

需要在工程中设置链接d3dx9.lib d3d9.lib。
由于文件中用到了GE_APP这个类，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。

源码下载

来看看AlphaBlend.h的定义:

 

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

 PURPOSE: 
    Define for alpha blend.
*************************************************************************************/

#ifndef ALPHA_BLEND_H
#define ALPHA_BLEND_H

struct CUSTOM_VERTEX
{
    float x, y, z;
    float nx, ny, nz;
};

#define CUSTOM_VERTEX_FVF   (D3DFVF_XYZ | D3DFVF_NORMAL)

class ALPHA_BLEND
{
private:
    IDirect3D9* _d3d;
    IDirect3DDevice9* _d3d_device;
    IDirect3DVertexBuffer9* _vertex_buffer1;
    IDirect3DVertexBuffer9* _vertex_buffer2;

public:
    ALPHA_BLEND();
    ~ALPHA_BLEND();

    bool Create_D3D_Device(HWND hwnd, bool full_screen = true);
    bool Init_Vertex_Buffer1();
    bool Init_Vertex_Buffer2();
    void Compute_Triangle_Normal(D3DXVECTOR3& v1, D3DXVECTOR3& v2, D3DXVECTOR3& v3, D3DVECTOR& normal);
    void Set_Camera();
    void Set_Point_Light();
    void Set_Object_Material(D3DCOLORVALUE& dif, D3DCOLORVALUE& amb, D3DCOLORVALUE& spe, 
                             D3DCOLORVALUE& emi, float power);
    void Render();
    void Release_COM_Object();
};

#endif

以上的头文件定义了两个三棱锥的顶点格式和顶点结构体，函数Init_Vertex_Buffer1个Init_Vertex_Buffer2分别用来装入这两个三棱锥的顶点数据，Render函数则设置了渲染管道流水线的 Alpha颜色混合状态值。

再来看看AlphaBlend.cpp的定义：

 

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

 PURPOSE: 
    Define for alpha blend.
*************************************************************************************/

#include "GE_COMMON.h"
#include "AlphaBlend.h"

//------------------------------------------------------------------------------------
// Constructor, initialize all pointer with NULL.
//------------------------------------------------------------------------------------
ALPHA_BLEND::ALPHA_BLEND()
{
    _d3d            = NULL;
    _d3d_device     = NULL;
    _vertex_buffer1 = NULL;
    _vertex_buffer2 = NULL;
}

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

//------------------------------------------------------------------------------------
// Create direct3D interface and direct3D device.
//------------------------------------------------------------------------------------
bool ALPHA_BLEND::Create_D3D_Device(HWND hwnd, bool full_screen)
{
    // Create a IDirect3D9 object and returns an interace to it.
    _d3d = Direct3DCreate9(D3D_SDK_VERSION);
    if(_d3d == NULL)
        return false;

    // retrieve adapter capability
    D3DCAPS9 d3d_caps;    
    _d3d->GetDeviceCaps(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, &d3d_caps);
    
    bool hardware_process_enable = (d3d_caps.DevCaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT ? true : false);

    // Retrieves the current display mode of the adapter.
    D3DDISPLAYMODE display_mode;
    if(FAILED(_d3d->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &display_mode)))
        return false;

    // set present parameter for direct3D device
    D3DPRESENT_PARAMETERS present_param;

    ZeroMemory(&present_param, sizeof(present_param));

    present_param.BackBufferWidth      = WINDOW_WIDTH;
    present_param.BackBufferHeight     = WINDOW_HEIGHT;
    present_param.BackBufferFormat     = display_mode.Format;
    present_param.BackBufferCount      = 1;
    present_param.hDeviceWindow        = hwnd;
    present_param.Windowed             = !full_screen;
    present_param.SwapEffect           = D3DSWAPEFFECT_FLIP;
    present_param.PresentationInterval = D3DPRESENT_INTERVAL_DEFAULT;

    // Creates a device to represent the display adapter.
    DWORD behavior_flags;

    behavior_flags = hardware_process_enable ?
 D3DCREATE_HARDWARE_VERTEXPROCESSING : D3DCREATE_SOFTWARE_VERTEXPROCESSING;

    if(FAILED(_d3d->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hwnd, behavior_flags, 
                                 &present_param, &_d3d_device)))
    {
        return false;
    }
    
    // create successfully
    return true;
}

//------------------------------------------------------------------------------------
// Initialize vertex buffer for cone.
//------------------------------------------------------------------------------------
bool ALPHA_BLEND::Init_Vertex_Buffer1()
{
    CUSTOM_VERTEX custom_vertex[12];
    
    D3DXVECTOR3 v[] = 
    {
        D3DXVECTOR3(5.0f, 6.0f, 5.0f),    // left triangle
        D3DXVECTOR3(6.0f, 0.0f, 3.0f),
        D3DXVECTOR3(1.0f, 0.0f, 7.0f),  
        D3DXVECTOR3(5.0f, 6.0f, 5.0f),    // right triangle
        D3DXVECTOR3(10.0f, 0.0f, 8.0f),
        D3DXVECTOR3(6.0f, 0.0f, 3.0f), 
        D3DXVECTOR3(5.0f, 6.0f, 5.0f),    // back triangle
        D3DXVECTOR3(1.0f, 0.0f, 7.0f),
        D3DXVECTOR3(10.0f, 0.0f, 8.0f),
        D3DXVECTOR3(1.0f, 0.0f, 7.0f),    // bottom triangle
        D3DXVECTOR3(6.0f, 0.0f, 3.0f),
        D3DXVECTOR3(10.0f, 0.0f, 8.0f)      
    };

    D3DVECTOR normal;

    // compute all triangle normal
    for(int i = 0; i < 12; i += 3)
    {
        // compute current triangle's normal
        Compute_Triangle_Normal(v[i], v[i+1], v[i+2], normal);

        // assign current vertex coordinate and current triangle normal to custom vertex array
        for(int j = 0; j < 3; j++)
        {
            int k = i + j;

            custom_vertex[k].x  = v[k].x;
            custom_vertex[k].y  = v[k].y;
            custom_vertex[k].z  = v[k].z;
            custom_vertex[k].nx = normal.x;
            custom_vertex[k].ny = normal.y;
            custom_vertex[k].nz = normal.z;
        }
    }

    BYTE* vertex_data;

    // create vertex buffer
    if(FAILED(_d3d_device->CreateVertexBuffer(12 * sizeof(CUSTOM_VERTEX), 0, CUSTOM_VERTEX_FVF,
                            D3DPOOL_DEFAULT, &_vertex_buffer1, NULL)))
    {
        return false;
    }

    // get data pointer to vertex buffer
    if(FAILED(_vertex_buffer1->Lock(0, 0, (void **) &vertex_data, 0)))
        return false;

    // copy custom vertex data into vertex buffer
    memcpy(vertex_data, custom_vertex, sizeof(custom_vertex));

    // unlock vertex buffer
    _vertex_buffer1->Unlock();

    return true;
}

//------------------------------------------------------------------------------------
// Initialize vertex buffer for cone.
//------------------------------------------------------------------------------------
bool ALPHA_BLEND::Init_Vertex_Buffer2()
{
    CUSTOM_VERTEX custom_vertex[12];

    float add = 1.3f;
    
    D3DXVECTOR3 v[] = 
    {
        D3DXVECTOR3(5.0f + add, 6.0f + add, 5.0f + add),    // left triangle
        D3DXVECTOR3(6.0f + add, 0.0f + add, 3.0f + add),
        D3DXVECTOR3(1.0f + add, 0.0f + add, 7.0f + add),  
        D3DXVECTOR3(5.0f + add, 6.0f + add, 5.0f + add),    // right triangle
        D3DXVECTOR3(10.0f + add, 0.0f + add, 8.0f + add),
        D3DXVECTOR3(6.0f + add, 0.0f + add, 3.0f + add), 
        D3DXVECTOR3(5.0f + add, 6.0f + add, 5.0f + add),    // back triangle
        D3DXVECTOR3(1.0f + add, 0.0f + add, 7.0f + add),
        D3DXVECTOR3(10.0f + add, 0.0f + add, 8.0f + add),
        D3DXVECTOR3(1.0f + add, 0.0f + add, 7.0f + add),    // bottom triangle
        D3DXVECTOR3(6.0f + add, 0.0f + add, 3.0f + add),
        D3DXVECTOR3(10.0f + add, 0.0f + add, 8.0f + add)      
    };

    D3DVECTOR normal;

    // compute all triangle normal
    for(int i = 0; i < 12; i += 3)
    {
        // compute current triangle's normal
        Compute_Triangle_Normal(v[i], v[i+1], v[i+2], normal);

        // assign current vertex coordinate and current triangle normal to custom vertex array
        for(int j = 0; j < 3; j++)
        {
            int k = i + j;

            custom_vertex[k].x  = v[k].x;
            custom_vertex[k].y  = v[k].y;
            custom_vertex[k].z  = v[k].z;
            custom_vertex[k].nx = normal.x;
            custom_vertex[k].ny = normal.y;
            custom_vertex[k].nz = normal.z;
        }
    }

    BYTE* vertex_data;

    // create vertex buffer
    if(FAILED(_d3d_device->CreateVertexBuffer(12 * sizeof(CUSTOM_VERTEX), 0, CUSTOM_VERTEX_FVF,
                            D3DPOOL_DEFAULT, &_vertex_buffer2, NULL)))
    {
        return false;
    }

    // get data pointer to vertex buffer
    if(FAILED(_vertex_buffer2->Lock(0, 0, (void **) &vertex_data, 0)))
        return false;

    // copy custom vertex data into vertex buffer
    memcpy(vertex_data, custom_vertex, sizeof(custom_vertex));

    // unlock vertex buffer
    _vertex_buffer2->Unlock();

    return true;
}

//------------------------------------------------------------------------------------
// Set camera position.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Set_Camera()
{
    D3DXVECTOR3 eye(-6.0, 1.5, 10.0);
    D3DXVECTOR3 at(6.0, 2.0, 3.0);
    D3DXVECTOR3 up(0.0, 1.0, 0.0);

    D3DXMATRIX view_matrix;

    // Builds a left-handed, look-at matrix.
    D3DXMatrixLookAtLH(&view_matrix, &eye, &at, &up);

    // Sets d3d device view transformation state.
    _d3d_device->SetTransform(D3DTS_VIEW, &view_matrix);

    D3DXMATRIX proj_matrix;

    // Builds a left-handed perspective projection matrix based on a field of view.
    D3DXMatrixPerspectiveFovLH(&proj_matrix, D3DX_PI/2, WINDOW_WIDTH / WINDOW_HEIGHT, 1.0, 1000.0);
    
    // Sets d3d device projection transformation state.
    _d3d_device->SetTransform(D3DTS_PROJECTION, &proj_matrix);
    // enable automatic normalization of vertex normals
    _d3d_device->SetRenderState(D3DRS_NORMALIZENORMALS, true);
}

//------------------------------------------------------------------------------------
// Set point light.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Set_Point_Light()
{
    D3DLIGHT9 light;

    // clear memory with 0
    ZeroMemory(&light, sizeof(D3DLIGHT9));

    light.Type          = D3DLIGHT_POINT;

    light.Diffuse.r     = 1.0;
    light.Diffuse.g     = 0.0;
    light.Diffuse.b     = 0.0;

    light.Ambient.r     = 0.0;
    light.Ambient.g     = 1.0;
    light.Ambient.b     = 0.0;

    light.Specular.r    = 0.0;
    light.Specular.g    = 0.0;
    light.Specular.b    = 0.0;
    
    light.Position.x    = 5.0;
    light.Position.y    = 6.0;
    light.Position.z    = -20.0;

    light.Attenuation0  = 1.0;
    light.Attenuation1  = 0.0;
    light.Attenuation2  = 0.0;

    light.Range         = 1000.0;

    // Assigns point lighting properties for this device
    _d3d_device->SetLight(0, &light);
    // enable point light
    _d3d_device->LightEnable(0, TRUE);
    // enable light 
    _d3d_device->SetRenderState(D3DRS_LIGHTING, TRUE);
    // add ambient light
    _d3d_device->SetRenderState(D3DRS_AMBIENT, D3DCOLOR_XRGB(50, 50, 50));
}

//------------------------------------------------------------------------------------
// Sets the material properties for the device.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Set_Object_Material(D3DCOLORVALUE& dif, D3DCOLORVALUE& amb, D3DCOLORVALUE& spe, 
                                       D3DCOLORVALUE& emi, float power)
{
    D3DMATERIAL9 material;

    material.Diffuse  = dif;
    material.Ambient  = amb;
    material.Specular = spe;
    material.Emissive = emi;
    material.Power    = power;

    // Sets the material properties for the device.
    _d3d_device->SetMaterial(&material);
}

//------------------------------------------------------------------------------------
// Compute triangle normal.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Compute_Triangle_Normal(D3DXVECTOR3& v1, D3DXVECTOR3& v2, D3DXVECTOR3& v3, D3DVECTOR& normal)
{
    D3DXVECTOR3 vec1 = v1 - v2;
    D3DXVECTOR3 vec2 = v1 - v3;
    D3DXVECTOR3 normal_vec;

    D3DXVec3Cross(&normal_vec, &vec1, &vec2);
    D3DXVec3Normalize(&normal_vec, &normal_vec);

    normal = (D3DVECTOR) normal_vec;
}

//------------------------------------------------------------------------------------
// Draw cones.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Render()
{
    if(_d3d_device == NULL)
        return;

    // clear surface with black
    _d3d_device->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0, 0);

    // begin scene
    _d3d_device->BeginScene();

    // 1) draw cone 1

    // Binds a vertex buffer to a device data stream.
    _d3d_device->SetStreamSource(0, _vertex_buffer1, 0, sizeof(CUSTOM_VERTEX));

    // Sets the current vertex stream declaration.
    _d3d_device->SetFVF(CUSTOM_VERTEX_FVF);

    // Renders a sequence of nonindexed, geometric primitives of the specified type from the current 
    // set of data input streams.
    _d3d_device->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 4);

    // enable alpha-blended transparency
    _d3d_device->SetRenderState(D3DRS_ALPHABLENDENABLE, true);
    
    // set alpha blend for source cone
    _d3d_device->SetRenderState(D3DRS_SRCBLEND, D3DBLEND_SRCALPHA);
    // set alpha blend for dest cone
    _d3d_device->SetRenderState(D3DRS_DESTBLEND, D3DBLEND_INVSRCALPHA);

    // 2) draw cone 2

    // Binds a vertex buffer to a device data stream. 
    _d3d_device->SetStreamSource(0, _vertex_buffer2, 0, sizeof(CUSTOM_VERTEX));

    // Sets the current vertex stream declaration.
    _d3d_device->SetFVF(CUSTOM_VERTEX_FVF);

    // draw square
    _d3d_device->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 4);

    // disable alpha blend for d3d device
    _d3d_device->SetRenderState(D3DRS_ALPHABLENDENABLE, false);

    // end scene
    _d3d_device->EndScene();

    // Presents the contents of the next buffer in the sequence of back buffers owned by the device.
    _d3d_device->Present(NULL, NULL, NULL, NULL);
}

//------------------------------------------------------------------------------------
// Release all COM object.
//------------------------------------------------------------------------------------
void ALPHA_BLEND::Release_COM_Object()
{
    Safe_Release(_vertex_buffer1);
    Safe_Release(_vertex_buffer2);
    Safe_Release(_d3d_device);
    Safe_Release(_d3d);
}

main.cpp的实现很简单，它首先调用类ALPHA_BLEND的函数创建两个三棱锥的顶点缓冲区，然后进行取景并设置材质光源，最后调用Render函数进行混色渲染。

 

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

 PURPOSE: 
    Test for alpha blending.
*************************************************************************************/

#define DIRECTINPUT_VERSION 0x0800

#include "GE_COMMON.h"
#include "GE_APP.h"
#include "AlphaBlend.h"

#pragma warning(disable : 4305 4996)

int WINAPI WinMain(HINSTANCE instance, HINSTANCE, LPSTR cmd_line, int cmd_show)
{
    GE_APP ge_app;
    ALPHA_BLEND alpha_blend;

    MSG msg = {0};

    // create window
    if(! ge_app.Create_Window("Alpha blending test", instance, cmd_show))
        return false;

    HWND hwnd = ge_app.Get_Window_Handle();    

    SetWindowPos(hwnd, 0, 0,0,0,0, SWP_NOSIZE);
    SetCursorPos(0, 0);
    
    // Create direct3D interface and direct3D device.
    if(! alpha_blend.Create_D3D_Device(hwnd, false))
        return false;

    // Initialize cone 1 vertex buffer with curstom vertex structure.
    if(! alpha_blend.Init_Vertex_Buffer1())
        return false;

    // Initialize cone 2 vertex buffer with curstom vertex structure.
    if(! alpha_blend.Init_Vertex_Buffer2())
        return false;
    
    // Set camera position.
    alpha_blend.Set_Camera();

    D3DCOLORVALUE dif = {1.0f, 1.0f, 1.0f, 0.6f};
    D3DCOLORVALUE amb = {1.0f, 1.0f, 1.0f, 0.0f};
    D3DCOLORVALUE spe = {0.0f, 0.0f, 0.0f, 0.0f};
    D3DCOLORVALUE emi = {0.0f, 0.0f, 0.0f, 0.0f};

    // Sets the material properties for the device.
    alpha_blend.Set_Object_Material(dif, amb, spe, emi, 0);

    // Set point light.
    alpha_blend.Set_Point_Light();

    // Draw all cones
    alpha_blend.Render();

    while(msg.message != WM_QUIT)
    {
        if(PeekMessage(&msg, NULL, 0,0 , PM_REMOVE))
        {
            TranslateMessage(&msg);
            DispatchMessage(&msg);
        }
    }    

    UnregisterClass(WINDOW_CLASS_NAME, instance);

    return true;
}
 

运行效果：