19. 多纹理贴图

多纹理贴图的基本要素就是使用多个纹理。创建和加载多个Direct3D纹理对象即可实现。当使用硬件多纹理渲染纹理时，要为每个顶点指定两套纹理坐标。这只需在顶点结构中另外添加两个浮点成员变量即可完成，即在FVF中用D3DFVF_TEX2替换D3DFVF_TEX。

code:

#include<d3d9.h>
#include<d3dx9.h>

#define WINDOW_CLASS    "UGPDX"
#define WINDOW_NAME     "D3D Multi-Texture Mapping"
#define WINDOW_WIDTH    640
#define WINDOW_HEIGHT   480

// Function Prototypes...
bool InitializeD3D(HWND hWnd, bool fullscreen);
bool InitializeObjects();
void RenderScene();
void Shutdown();


// Direct3D object and device.
LPDIRECT3D9 g_D3D = NULL;
LPDIRECT3DDEVICE9 g_D3DDevice = NULL;

// Matrices.
D3DXMATRIX g_projection;
D3DXMATRIX g_ViewMatrix;

// Vertex buffer to hold the geometry.
LPDIRECT3DVERTEXBUFFER9 g_VertexBuffer = NULL;

// Holds a texture image.
LPDIRECT3DTEXTURE9 g_Texture = NULL;
LPDIRECT3DTEXTURE9 g_Texture2 = NULL;

// A structure for our custom vertex type
struct stD3DVertex
{
    float x, y, z;
    unsigned long color;
    float tu, tv;
    float tu2, tv2;
};

// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_VERTEX (D3DFVF_XYZ | D3DFVF_DIFFUSE | D3DFVF_TEX2)


LRESULT WINAPI MsgProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    switch(msg)
    {
    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
        break;

    case WM_KEYUP:
        if(wParam == VK_ESCAPE) PostQuitMessage(0);
        break;
    }

    return DefWindowProc(hWnd, msg, wParam, lParam);
}


int WINAPI WinMain(HINSTANCE hInst, HINSTANCE prevhInst, LPSTR cmdLine, int show)
{
    // Register the window class
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
        GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
        WINDOW_CLASS, NULL };
    RegisterClassEx(&wc);

    // Create the application's window
    HWND hWnd = CreateWindow(WINDOW_CLASS, WINDOW_NAME, WS_OVERLAPPEDWINDOW,
        100, 100, WINDOW_WIDTH, WINDOW_HEIGHT,
        GetDesktopWindow(), NULL, wc.hInstance, NULL);

    // Initialize Direct3D
    if(InitializeD3D(hWnd, false))
    {
        // Show the window
        ShowWindow(hWnd, SW_SHOWDEFAULT);
        UpdateWindow(hWnd);

        // Enter the message loop
        MSG msg;
        ZeroMemory(&msg, sizeof(msg));

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

    // Release any and all resources.
    Shutdown();

    // Unregister our window.
    UnregisterClass(WINDOW_CLASS, wc.hInstance);
    return 0;
}


bool InitializeD3D(HWND hWnd, bool fullscreen)
{
    D3DDISPLAYMODE displayMode;

    // Create the D3D object.
    g_D3D = Direct3DCreate9(D3D_SDK_VERSION);
    if(g_D3D == NULL) return false;

    // Get the desktop display mode.
    if(FAILED(g_D3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &displayMode)))
        return false;

    // Set up the structure used to create the D3DDevice
    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory(&d3dpp, sizeof(d3dpp));

    if(fullscreen)
    {
        d3dpp.Windowed = FALSE;
        d3dpp.BackBufferWidth = WINDOW_WIDTH;
        d3dpp.BackBufferHeight = WINDOW_HEIGHT;
    }
    else
        d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = displayMode.Format;

    // Create the D3DDevice
    if(FAILED(g_D3D->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
        D3DCREATE_SOFTWARE_VERTEXPROCESSING, &d3dpp, &g_D3DDevice)))
    {
        return false;
    }

    // Initialize any objects we will be displaying.
    if(!InitializeObjects()) return false;

    return true;
}


bool InitializeObjects()
{
    // Fill in our structure to draw an object.
    // x, y, z, color, texture coords.
    stD3DVertex objData[] =
    {
        {-0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 1.0f, 0.0f, 1.0f},
        {0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 1.0f, 1.0f, 1.0f},
        {0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 0.0f, 1.0f, 0.0f},

        {0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 1.0f, 0.0f, 1.0f, 0.0f},
        {-0.3f, 0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 0.0f, 0.0f, 0.0f},
        {-0.3f, -0.4f, 0.0f, D3DCOLOR_XRGB(255,255,255), 0.0f, 1.0f, 0.0f, 1.0f}
    };

    // Create the vertex buffer.
    if(FAILED(g_D3DDevice->CreateVertexBuffer(sizeof(objData), 0,
        D3DFVF_VERTEX, D3DPOOL_DEFAULT,
        &g_VertexBuffer, NULL))) return false;

    // Fill the vertex buffer.
    void *ptr;

    if(FAILED(g_VertexBuffer->Lock(0, sizeof(objData),
        (void**)&ptr, 0))) return false;

    memcpy(ptr, objData, sizeof(objData));

    g_VertexBuffer->Unlock();


    // Load the texture image from file.
    if(D3DXCreateTextureFromFile(g_D3DDevice, "Image1.bmp",
        &g_Texture) != D3D_OK) return false;

    if(D3DXCreateTextureFromFile(g_D3DDevice, "Image2.bmp",
        &g_Texture2) != D3D_OK) return false;


    // Set default rendering states.
    g_D3DDevice->SetRenderState(D3DRS_LIGHTING, FALSE);
    g_D3DDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_NONE);


    // Set the projection matrix.
    D3DXMatrixPerspectiveFovLH(&g_projection, 45.0f,
        WINDOW_WIDTH/WINDOW_HEIGHT, 0.1f, 1000.0f);

    g_D3DDevice->SetTransform(D3DTS_PROJECTION, &g_projection);


    // Define camera information.
    D3DXVECTOR3 cameraPos(0.0f, 0.0f, -1.0f);
    D3DXVECTOR3 lookAtPos(0.0f, 0.0f, 0.0f);
    D3DXVECTOR3 upDir(0.0f, 1.0f, 0.0f);

    // Build view matrix.
    D3DXMatrixLookAtLH(&g_ViewMatrix, &cameraPos,
        &lookAtPos, &upDir);

    return true;
}


void RenderScene()
{
    // Clear the backbuffer.
    g_D3DDevice->Clear(0, NULL, D3DCLEAR_TARGET,
        D3DCOLOR_XRGB(0,0,0), 1.0f, 0);

    // Begin the scene.  Start rendering.
    g_D3DDevice->BeginScene();

    // Apply the view (camera).
    g_D3DDevice->SetTransform(D3DTS_VIEW, &g_ViewMatrix);

    // Set the texture stages for the first texture unit (image).
    g_D3DDevice->SetSamplerState(0, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
    g_D3DDevice->SetSamplerState(0, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);

    //设置索引为0的Texture的Stage的颜色混合操作（RGB混合）为MODULATE（各颜色分量相乘）
    //COLORARG1与COLORARG2分别指代该Texture Stage要混合的两个纹理（或一个纹理和一个顶点集）
    //的颜色部分（RGB）
    //该纹理使用纹理坐标的索引设置为0(共有2套纹理坐标)
    g_D3DDevice->SetTextureStageState(0, D3DTSS_TEXCOORDINDEX, 0);
    //纹理的颜色混合方式设置为D3DTOP_MODULATE（将参数的每个成分相乘） 
    g_D3DDevice->SetTextureStageState(0, D3DTSS_COLOROP,   D3DTOP_MODULATE);
    //颜色混合的第一个参数设置为D3DTA_TEXTURE(D3DTA_TEXTURE就是取该纹理本身的颜色)
    g_D3DDevice->SetTextureStageState(0, D3DTSS_COLORARG1, D3DTA_TEXTURE);
    //颜色混合的第二个参数设置为D3DTA_DIFFUSE是取按顶点间插值计算出的散射光颜色
    g_D3DDevice->SetTextureStageState(0, D3DTSS_COLORARG2, D3DTA_DIFFUSE);

    // Set the texture stages for the second texture unit (image).
    g_D3DDevice->SetSamplerState(1, D3DSAMP_MINFILTER, D3DTEXF_LINEAR);
    g_D3DDevice->SetSamplerState(1, D3DSAMP_MAGFILTER, D3DTEXF_LINEAR);

    g_D3DDevice->SetTextureStageState(1, D3DTSS_TEXCOORDINDEX, 1);
    g_D3DDevice->SetTextureStageState(1, D3DTSS_COLOROP, D3DTOP_MODULATE);
    g_D3DDevice->SetTextureStageState(1, D3DTSS_COLORARG1, D3DTA_TEXTURE);
    // D3DTA_CURRENT是取上一个Texture Stage计算出的颜色值
    g_D3DDevice->SetTextureStageState(1, D3DTSS_COLORARG2, D3DTA_CURRENT);

    // Draw square.
    g_D3DDevice->SetTexture(0, g_Texture);
    g_D3DDevice->SetTexture(1, g_Texture2);
    g_D3DDevice->SetStreamSource(0, g_VertexBuffer, 0, sizeof(stD3DVertex));
    g_D3DDevice->SetFVF(D3DFVF_VERTEX);
    g_D3DDevice->DrawPrimitive(D3DPT_TRIANGLELIST, 0, 2);

    // End the scene.  Stop rendering.
    g_D3DDevice->EndScene();

    // Display the scene.
    g_D3DDevice->Present(NULL, NULL, NULL, NULL);
}


void Shutdown()
{
    if(g_D3DDevice != NULL) g_D3DDevice->Release();
    g_D3DDevice = NULL;

    if(g_D3D != NULL) g_D3D->Release();
    g_D3D = NULL;

    if(g_VertexBuffer != NULL) g_VertexBuffer->Release();
    g_VertexBuffer = NULL;

    if(g_Texture != NULL) g_Texture->Release();
    g_Texture = NULL;

    if(g_Texture2 != NULL) g_Texture2->Release();
    g_Texture2 = NULL;
}

/*
HRESULT SetTextureStageState(
DWORD Stage,   //   //当前设置的多级纹理的索引(指第几层纹理)0,1,2,3,4,5,6,7
D3DTEXTURESTAGESTATETYPE Type, // 纹理渲染状态的类型(所设置的纹理阶段),定义对该纹理的哪个属进行设置，值很多。
DWORD Value    //设置阶段的标识符,指的是前面所选属性的值
);

*/

　　

　　

  InitializeObjects()函数首先创建了一个对象，它指定了顶点位置、颜色和两套纹理坐标。当谈到硬件多纹理贴图时，即使这两套纹理坐标的值相同，也必须指定。使用两套纹理坐标可以为每个顶点使用不同的坐标。这是希望出现的特征，尤其是在采用如光照映射这样的使用不同纹理坐标的技术时，更是如此。

        对象被创建和放置在顶点缓存中以后，加载了两个纹理对象。同样可以使用在第一个纹理映射演示程序中的方式实现多纹理贴图，而这一次是在两个纹理对象而不是一个纹理对象上使用纹理贴图。加载纹理文件后，就采用以前的方式调用该函数。

RenderScene()函数也用于清屏、启动新场景和设置视图矩阵。之后程序调用SetTextureStageState()函数为第一个纹理设置多纹理状态。这里的Stage参数是要处理的纹理索引，Type是所设置的纹理阶段，Value是设置阶段的标识符。在谈到纹理索引时，第一个纹理单元为0，第二个为1，依次类推。

HRESULT SetTextureStageState(
DWORD Stage,   //   //当前设置的多级纹理的索引(指第几层纹理)0,1,2,3,4,5,6,7
D3DTEXTURESTAGESTATETYPE Type, // 纹理渲染状态的类型(所设置的纹理阶段),定义对该纹理的哪个属进行设置，值很多。
DWORD Value    //设置阶段的标识符,指的是前面所选属性的值
);

　　为了给第一个纹理单元设置多纹理贴图，先要将D3DTSS_TEXCOORDINDEX的纹理索引设为0，这样Direct3D就会知道正在处理第一个索引。接下来告诉Direct3D通过将D3DTSS_COLORARG2分别设置参数1和参数2。方法是使用D3DTA_TEXTURE将纹理发送给参数1，使用D3DTA_DIFFUSE将对象颜色发送给参数2。

        所要做的全部工作就是设置第一个纹理单元。以完全相同的方式处理第二个纹理，但是调整纹理时所用的第二个参数，就是用第二个纹理调整第一个纹理的结果。这样可以如期望的那样用第一个纹理和顶点颜色混合第二个纹理。

        设置纹理阶段之后，使用SetTexture()函数绑定这两个纹理。如所知道的一样，SetTexture()函数的参数包括纹理单位以及要设置的纹理对象。这之后，对程序的其余内容像以往一样进行处理。