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高級紋理映射技術（11）

要渲染看起來真實的場景，最好是使用高分辨率而且顏色豐富的紋理，但這樣的紋理可能會耗費大量的內存，例如，一張每像素16位顏色的256 x 256紋理將使用128KB的內存。如果在該紋理中使用多級漸進紋理，還需要額外的43KB內存。一個使用50張這種紋理的場景將需要8MB的內存，如果需要更強的真實性，可以使用每像素32位顏色的512 x 512紋理，但那就需要8倍的內存。

為了減少紋理消耗的系統帶寬和內存空間，Direct3D支持紋理壓縮和實時解壓，即DXT紋理壓縮。壓縮后的紋理被存儲在Direct3D紋理指針中，當Direct3D渲染物體時，Direct3D引擎自動對紋理進行解壓。應用DXT壓縮紋理不僅可以節省內存空間，而且能有效地降低紋理傳輸帶寬，提高圖形系統的整體性能。

隨著DirectX對紋理壓縮格式的推廣，目前大部分顯卡都支持DXT壓縮紋理，而且DXT壓縮紋理在圖形質量和運行速度之間取得了很好的平衡。

DXT紋理壓縮格式

DXT是一種DirectDraw表面，它以壓縮形式存儲圖形數據，該表面可以節省大量的系統帶寬和內存。即使不直接使用DXT表面渲染，也可以通過DXT格式創建紋理的方法節省磁盤空間。Direct3D提供了D3DFMT_DXT1 ~ D3DFMT_DXT5共5種壓縮紋理格式。其中，D3DFMT_DXT1支持15位RGB和1位alpha圖形格式，D3DFMT_DXT2、D3DFMT_DXT3支持12位RGB和4位alpha，D3DFMT_DXT4、D3DFMT_DXT5則采取了線性插值方式生成alpha。

DXT1格式的壓縮比例是4 : 1（4x4塊16位RGB紋理元素可壓縮為64位，2個16位RGB565值和16個2位索引），這樣的壓縮比并不很高，但足以有效地將3D加速卡用于存儲紋理的容量提高4倍，如下圖所示：

Direct3D支持5中DXT格式壓縮：

FOURCC	Description	Alpha premultiplied?
DXT1	Opaque/1-bit alpha	N/A
DXT2	Explicit alpha	Yes
DXT3	Explicit alpha	No
DXT4	Interpolated alpha	Yes
DXT5	Interpolated alpha	No

使用DXT壓縮紋理

使用DXT壓縮紋理前，必須先調用IDirect3D9::CheckDeviceFormat()，將表面格式設置為D3DFMT_DXT1 ~ D3DFMT_DXT5中的任意值，查詢當前設備是否支持DXT壓縮紋理：

// check whether device support DXT compressed texture
if(FAILED(pD3D->CheckDeviceFormat(pCaps->AdapterOrdinal, pCaps->DeviceType, AdapterFormat, 0, D3DRTYPE_TEXTURE, 
								   D3DFMT_DXT1)))
	return false;

如果當前設備支持DXT壓縮紋理，就可以直接創建DXT壓縮紋理，并可以通過IDirect3DDevice9::SetTexture()函數設置DXT壓縮紋理，將其映射到物體表面。如果當前設備不支持DXT壓縮紋理，仍然可以DXT壓縮格式存儲紋理，但在使用該紋理渲染圖形前，必須將DXT壓縮格式的紋理轉換為當前設備支持的格式。

在使用函數IDirect3DDevice9::CreateTexture()創建紋理時，將參數Format設置為壓縮紋理格式D3DFMT_DXT1 ~ D3DFMT_DXT5中的任意值，可以創建指定壓縮格式的紋理，也可以通過函數D3DXCreateTextureFromFileEx()從磁盤文件中生成DXT壓縮紋理：

V_RETURN(D3DXCreateTextureFromFileExW(pd3dDevice, L"texture.jpg", 0, 0, 5, 0, D3DFMT_DXT1, D3DPOOL_MANAGED,
D3DX_DEFAULT, D3DX_DEFAULT, 0xFF000000, NULL, NULL, &g_texture));

可以通過DirectX SDK提供的紋理編輯工具"DirectX Texture Editor"，創建壓縮格式的紋理文件（后綴為DDS的紋理文件），或將其他格式的紋理文件轉換為壓縮格式的紋理文件。

在創建好壓縮紋理之后，就可以和前面一樣設置紋理及各項紋理渲染狀態，最后進行渲染。如果當前設備支持DXT壓縮紋理，那么在使用DXT紋理渲染圖形時，Direct3D引擎會自動進行紋理壓縮，如果當前設備不支持DXT壓縮紋理，這時使用DXT壓縮紋理和使用普通的非壓縮紋理完全相同。

當使用大量紋理貼圖渲染復雜場景時，通過使用DXT壓縮紋理可以有效提高程序運行性能。

紋理管理

如果顯卡中只有64MB的視頻內存，就應該考慮將哪些紋理加載和保留在內存中。可以編寫一個算法讓計算機來自動考慮這些問題，那么這個算法的任務是什么呢？它需要跟蹤可用的紋理內存總數，并了解哪些紋理是經常用到的，而哪些紋理是很少用到的。至少，這個紋理管理算法必須能決定哪些現有的紋理資源可以通過一張紋理圖來重新加載，以及應該銷毀哪些表面，然后由新的紋理資源取而代之。

Direct3D有一個自動的紋理管理系統，當通過CreateTexture()創建一個紋理對象時，將Pool參數指定為D3DPOOL_MANAGED，就是向Direct3D請求該系統的支持。紋理管理器通過一個時間戳來跟蹤紋理的使用情況，這個時間戳用于記錄每個紋理對象最后被使用的時間。紋理管理器通過"最近最少使用"算法來決定哪些紋理應從視頻內存中移除，若有兩個紋理對象同時滿足移除條件，則根據紋理屬性來做進一步的判斷。如果它們具有相同的優先級，則移除最近最少使用的紋理，如果它們具有相同的時間戳，則移除低優先級的紋理。

通過為紋理表面調用IDirect3DResource9::SetPriority()函數，可以給托管的紋理賦予一個優先級，該函數聲明如下：

Assigns the resource-management priority for this resource.

DWORD SetPriority(
  DWORD PriorityNew
);

Parameters

PriorityNew: [in] DWORD value that specifies the new resource-management priority for the resource.

Return Values

Returns the previous priority value for the resource.

Remarks

SetPriority is used for priority control of managed resources. This method returns 0 on non-managed resources.

Priorities are used to determine when managed resources are to be removed from memory. A resource assigned a low priority is removed before a resource with a high priority. If two resources have the same priority, the resource that was used more recently is kept in memory; the other resource is removed. Managed resources have a default priority of 0.

原圖：

DXT壓縮后：

主程序:

#include "dxstdafx.h"
#include "resource.h"

#pragma warning(disable : 4127)

#define IDC_TOGGLE_FULLSCREEN        1
#define IDC_TOGGLE_REF                2
#define IDC_CHANGE_DEVICE            3

#define release_com(p)    do { if(p) { (p)->Release(); (p) = NULL; } } while(0)

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

#define D3DFVF_CUSTOM_VERTEX    (D3DFVF_XYZ | D3DFVF_TEX1)

ID3DXFont*                    g_font;
ID3DXSprite*                g_text_sprite;
bool                        g_show_help;

CDXUTDialogResourceManager    g_dlg_resource_manager;
CD3DSettingsDlg                g_settings_dlg;
CDXUTDialog                    g_button_dlg;

IDirect3DVertexBuffer9*        g_vertex_buffer;
IDirect3DTexture9*            g_texture;

//--------------------------------------------------------------------------------------
// Rejects any devices that aren't acceptable by returning false
//--------------------------------------------------------------------------------------
bool CALLBACK IsDeviceAcceptable( D3DCAPS9* pCaps, D3DFORMAT AdapterFormat,
                                  D3DFORMAT BackBufferFormat, bool bWindowed, void* pUserContext )
{
    // Typically want to skip backbuffer formats that don't support alpha blending

    IDirect3D9* pD3D = DXUTGetD3DObject();

    if( FAILED( pD3D->CheckDeviceFormat( pCaps->AdapterOrdinal, pCaps->DeviceType, AdapterFormat,
                    D3DUSAGE_QUERY_POSTPIXELSHADER_BLENDING, D3DRTYPE_TEXTURE, BackBufferFormat ) ) )
        return false;

    // check whether device support DXT compressed texture
    if(FAILED(pD3D->CheckDeviceFormat(pCaps->AdapterOrdinal, pCaps->DeviceType, AdapterFormat, 0, D3DRTYPE_TEXTURE,
                                       D3DFMT_DXT1)))
        return false;

    return true;
}

//--------------------------------------------------------------------------------------
// Before a device is created, modify the device settings as needed.
//--------------------------------------------------------------------------------------
bool CALLBACK ModifyDeviceSettings( DXUTDeviceSettings* pDeviceSettings, const D3DCAPS9* pCaps, void* pUserContext )
{
    // If video card does not support hardware vertex processing, then uses sofaware vertex processing.
    if((pCaps->DevCaps & D3DDEVCAPS_HWTRANSFORMANDLIGHT) == 0)
        pDeviceSettings->BehaviorFlags = D3DCREATE_SOFTWARE_VERTEXPROCESSING;

    static bool is_first_time = true;

    if(is_first_time)
    {
        is_first_time = false;

        // if using reference device, then pop a warning message box.
        if(pDeviceSettings->DeviceType == D3DDEVTYPE_REF)
            DXUTDisplaySwitchingToREFWarning();
    }

    return true;
}

//--------------------------------------------------------------------------------------
// Create any D3DPOOL_MANAGED resources here
//--------------------------------------------------------------------------------------
HRESULT CALLBACK OnCreateDevice( IDirect3DDevice9* pd3dDevice,
                                 const D3DSURFACE_DESC* pBackBufferSurfaceDesc,
                                 void* pUserContext )
{
    HRESULT    hr;

    V_RETURN(g_dlg_resource_manager.OnCreateDevice(pd3dDevice));
    V_RETURN(g_settings_dlg.OnCreateDevice(pd3dDevice));

    D3DXCreateFont(pd3dDevice, 18, 0, FW_BOLD, 1, FALSE, DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, DEFAULT_QUALITY,
                   DEFAULT_PITCH | FF_DONTCARE, L"Arial", &g_font);

    V_RETURN(D3DXCreateTextureFromFileExW(pd3dDevice, L"texture.jpg", 0, 0, 5, 0, D3DFMT_DXT1, D3DPOOL_MANAGED,
                                          D3DX_DEFAULT, D3DX_DEFAULT, 0xFF000000, NULL, NULL, &g_texture));

    // create vertex buffer and fill data

    sCustomVertex vertices[] =
    {
        { -3,   -3,  0.0f,  0.0f, 1.0f },
        { -3,    3,  0.0f,  0.0f, 0.0f },
        {  3,   -3,  0.0f,  1.0f, 1.0f },
        {  3,    3,  0.0f,  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();

    return S_OK;
}

//--------------------------------------------------------------------------------------
// Create any D3DPOOL_DEFAULT resources here
//--------------------------------------------------------------------------------------
HRESULT CALLBACK OnResetDevice( IDirect3DDevice9* pd3dDevice,
                                const D3DSURFACE_DESC* pBackBufferSurfaceDesc,
                                void* pUserContext )
{
    HRESULT hr;

    V_RETURN(g_dlg_resource_manager.OnResetDevice());
    V_RETURN(g_settings_dlg.OnResetDevice());
    V_RETURN(g_font->OnResetDevice());
    V_RETURN(D3DXCreateSprite(pd3dDevice, &g_text_sprite));

    // set dialog position and size

    g_button_dlg.SetLocation(pBackBufferSurfaceDesc->Width - 170, 0);
    g_button_dlg.SetSize(170, 170);

    // setup view matrix

    D3DXMATRIX mat_view;
    D3DXVECTOR3 eye(0.0f, 0.0f, -8.0f);
    D3DXVECTOR3  at(0.0f, 0.0f,  0.0f);
    D3DXVECTOR3  up(0.0f, 1.0f,  0.0f);

    D3DXMatrixLookAtLH(&mat_view, &eye, &at, &up);
    pd3dDevice->SetTransform(D3DTS_VIEW, &mat_view);

    // set projection matrix
    D3DXMATRIX mat_proj;
    float aspect = (float)pBackBufferSurfaceDesc->Width / pBackBufferSurfaceDesc->Height;
    D3DXMatrixPerspectiveFovLH(&mat_proj, D3DX_PI/4, aspect, 1.0f, 100.0f);
    pd3dDevice->SetTransform(D3DTS_PROJECTION, &mat_proj);

    // set texture and texture stage state and sample state
    pd3dDevice->SetTexture(0, g_texture);
    pd3dDevice->SetTextureStageState(0, D3DTSS_COLORARG1,    D3DTA_TEXTURE);
    pd3dDevice->SetTextureStageState(0, D3DTSS_COLOROP,        D3DTOP_SELECTARG1);
    pd3dDevice->SetTextureStageState(0, D3DTSS_ALPHAOP,        D3DTOP_DISABLE);
    pd3dDevice->SetSamplerState(0, D3DSAMP_MIPFILTER, D3DTEXF_LINEAR);

    pd3dDevice->SetStreamSource(0, g_vertex_buffer, 0, sizeof(sCustomVertex));
    pd3dDevice->SetFVF(D3DFVF_CUSTOM_VERTEX);

    return S_OK;
}

//--------------------------------------------------------------------------------------
// Release resources created in the OnResetDevice callback here
//--------------------------------------------------------------------------------------
void CALLBACK OnLostDevice( void* pUserContext )
{
    g_dlg_resource_manager.OnLostDevice();
    g_settings_dlg.OnLostDevice();
    g_font->OnLostDevice();

    release_com(g_text_sprite);
}

//--------------------------------------------------------------------------------------
// Release resources created in the OnCreateDevice callback here
//--------------------------------------------------------------------------------------
void CALLBACK OnDestroyDevice( void* pUserContext )
{
    g_dlg_resource_manager.OnDestroyDevice();
    g_settings_dlg.OnDestroyDevice();

    release_com(g_font);
    release_com(g_vertex_buffer);
    release_com(g_texture);
}

//--------------------------------------------------------------------------------------
// Handle updates to the scene
//--------------------------------------------------------------------------------------
void CALLBACK OnFrameMove( IDirect3DDevice9* pd3dDevice, double fTime, float fElapsedTime, void* pUserContext )
{
}

//--------------------------------------------------------------------------------------
// Render the helper information
//--------------------------------------------------------------------------------------
void RenderText()
{
    CDXUTTextHelper text_helper(g_font, g_text_sprite, 20);

    text_helper.Begin();

    // show frame and device states
    text_helper.SetInsertionPos(5, 5);
    text_helper.SetForegroundColor( D3DXCOLOR(1.0f, 0.475f, 0.0f, 1.0f) );
    text_helper.DrawTextLine( DXUTGetFrameStats(true) );
    text_helper.DrawTextLine( DXUTGetDeviceStats() );

    // show helper information

    const D3DSURFACE_DESC* surface_desc = DXUTGetBackBufferSurfaceDesc();

    if(g_show_help)
    {
        text_helper.SetInsertionPos(10, surface_desc->Height - 15 * 6);
        text_helper.SetForegroundColor( D3DXCOLOR(1.0f, 0.475f, 0.0f, 1.0f) );
        text_helper.DrawTextLine(L"Controls (F1 to hide):");

        text_helper.SetInsertionPos(40, surface_desc->Height - 15 * 4);
        text_helper.DrawTextLine(L"Quir: ESC");
    }
    else
    {
        text_helper.SetInsertionPos(10, surface_desc->Height - 15 * 4);
        text_helper.SetForegroundColor( D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f) );
        text_helper.DrawTextLine(L"Press F1 for help");
    }

    text_helper.End();
}

//--------------------------------------------------------------------------------------
// Render the scene
//--------------------------------------------------------------------------------------
void CALLBACK OnFrameRender( IDirect3DDevice9* pd3dDevice, double fTime, float fElapsedTime, void* pUserContext )
{
    HRESULT hr;

    if(g_settings_dlg.IsActive())
    {
        g_settings_dlg.OnRender(fElapsedTime);
        return;
    }

    // Clear the render target and the zbuffer
    V( pd3dDevice->Clear(0, NULL, D3DCLEAR_TARGET | D3DCLEAR_ZBUFFER, D3DCOLOR_ARGB(0, 0, 0, 0), 1.0f, 0) );

    // Render the scene
    if( SUCCEEDED( pd3dDevice->BeginScene() ) )
    {
        pd3dDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, 2);
        RenderText();
        V(g_button_dlg.OnRender(fElapsedTime));

        V( pd3dDevice->EndScene() );
    }
}

//--------------------------------------------------------------------------------------
// Handle messages to the application
//--------------------------------------------------------------------------------------
LRESULT CALLBACK MsgProc( HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam,
                          bool* pbNoFurtherProcessing, void* pUserContext )
{
    *pbNoFurtherProcessing = g_dlg_resource_manager.MsgProc(hWnd, uMsg, wParam, lParam);
    if(*pbNoFurtherProcessing)
        return 0;

    if(g_settings_dlg.IsActive())
    {
        g_settings_dlg.MsgProc(hWnd, uMsg, wParam, lParam);
        return 0;
    }

    *pbNoFurtherProcessing = g_button_dlg.MsgProc(hWnd, uMsg, wParam, lParam);
    if(*pbNoFurtherProcessing)
        return 0;

    return 0;
}

//--------------------------------------------------------------------------------------
// Handle keybaord event
//--------------------------------------------------------------------------------------
void CALLBACK OnKeyboardProc(UINT charater, bool is_key_down, bool is_alt_down, void* user_context)
{
    if(is_key_down)
    {
        switch(charater)
        {
        case VK_F1:
            g_show_help = !g_show_help;
            break;
        }
    }
}

//--------------------------------------------------------------------------------------
// Handle events for controls
//--------------------------------------------------------------------------------------
void CALLBACK OnGUIEvent(UINT event, int control_id, CDXUTControl* control, void* user_context)
{
    switch(control_id)
    {
    case IDC_TOGGLE_FULLSCREEN:
        DXUTToggleFullScreen();
        break;

    case IDC_TOGGLE_REF:
        DXUTToggleREF();
        break;

    case IDC_CHANGE_DEVICE:
        g_settings_dlg.SetActive(true);
        break;
    }
}

//--------------------------------------------------------------------------------------
// Initialize dialogs
//--------------------------------------------------------------------------------------
void InitDialogs()
{
    g_settings_dlg.Init(&g_dlg_resource_manager);
    g_button_dlg.Init(&g_dlg_resource_manager);

    g_button_dlg.SetCallback(OnGUIEvent);

    int x = 35, y = 10, width = 125, height = 22;

    g_button_dlg.AddButton(IDC_TOGGLE_FULLSCREEN, L"Toggle full screen", x, y,         width, height);
    g_button_dlg.AddButton(IDC_TOGGLE_REF,          L"Toggle REF (F3)",     x, y += 24, width, height);
    g_button_dlg.AddButton(IDC_CHANGE_DEVICE,      L"Change device (F2)", x, y += 24, width, height, VK_F2);
}

//--------------------------------------------------------------------------------------
// Initialize everything and go into a render loop
//--------------------------------------------------------------------------------------
INT WINAPI WinMain( HINSTANCE, HINSTANCE, LPSTR, int )
{
    // Enable run-time memory check for debug builds.
#if defined(DEBUG) | defined(_DEBUG)
    _CrtSetDbgFlag( _CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF );
#endif

    // Set the callback functions
    DXUTSetCallbackDeviceCreated( OnCreateDevice );
    DXUTSetCallbackDeviceReset( OnResetDevice );
    DXUTSetCallbackDeviceLost( OnLostDevice );
    DXUTSetCallbackDeviceDestroyed( OnDestroyDevice );
    DXUTSetCallbackMsgProc( MsgProc );
    DXUTSetCallbackFrameRender( OnFrameRender );
    DXUTSetCallbackFrameMove( OnFrameMove );
    DXUTSetCallbackKeyboard(OnKeyboardProc);

    // TODO: Perform any application-level initialization here
    InitDialogs();

    // Initialize DXUT and create the desired Win32 window and Direct3D device for the application
    DXUTInit( true, true, true ); // Parse the command line, handle the default hotkeys, and show msgboxes
    DXUTSetCursorSettings( true, true ); // Show the cursor and clip it when in full screen
    DXUTCreateWindow( L"TEX Compressed Texture" );
    DXUTCreateDevice( D3DADAPTER_DEFAULT, true, 800, 600, IsDeviceAcceptable, ModifyDeviceSettings );

    // Start the render loop
    DXUTMainLoop();

    // TODO: Perform any application-level cleanup here

    return DXUTGetExitCode();
}

下載示例工程

posted on 2008-05-22 18:08 lovedday 閱讀(3930) 評論(1) 編輯收藏引用

# re: 高級紋理映射技術（11） 2011-08-12 00:25 頁碼件

青青草原综合久久大伊人导航_色综合久久天天综合_日日噜噜夜夜狠狠久久丁香五月_热久久这里只有精品

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高級紋理映射技術（11）

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青青草原综合久久大伊人导航_色综合久久天天综合_日日噜噜夜夜狠狠久久丁香五月_热久久这里只有精品

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高級紋理映射技術（11）

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# re: 高級紋理映射技術（11） 2011-08-12 00:25 頁碼件

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