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directx学习之在屏幕上画一个三角形

2024-08-08 16:16:05   219人阅读

前一张已经输出了一个背景为紫色的屏幕，这一节的目标是在该屏幕上输出一个三角形。下面将逐一介绍建立一个三角形的过程。


一个三角形有三个点，叫做顶点。三个点的不同的集合可以建立不同的三角形。能让GPU创建一个三角形，必须将三个顶点的位置告诉它。下面是一个2D的例子。


怎么将三个点的数据传给GPU？

在d3d10中，顶点数据被存在一个缓存资源中。但是应该申请多大的缓存，这就是接下来的问题。

一个顶点就是一个位置，通常也包含一些其他的属性，比如颜色，纹理协调等。顶点结构就定义了那些属性在内存中的位置。

类似C语言的结构体，一个顶点通常被一个结构体来表示。顶点的大小就是结构体的大小。

在这里，我们只关心顶点的位置，因此我们定义我们自己的结构体仅有一个D3DXVECTOR3。整个类型是3个float点的容器，代表位置。

struct SimpleVertex

{

    D3DXVECTOR3 pos;//position

};


现在如果将上面的结构传给GPU，对它来讲，这就是一块内存区域。为了从缓存中提取有用的属性信息，GPU必须知道我们设置的结构体的布局，为了达到这个目的，我们使用输入布局。

在D3D10中，输入布局也是一个描述结构体的D3D10对象。

每一个顶点的属性可以被D3D10_INPUT_ELEMENT_DESC来描述，应用程序定义一个数组包含一个或者多个D3D10_INPUT_ELEMENT_DESC，然后用该数组作为输入布局来描述顶点。

<span style="font-family:KaiTi_GB2312;font-size:18px;">typedef struct D3D10_INPUT_ELEMENT_DESC {
  LPCSTR                     SemanticName;
  UINT                       SemanticIndex;
  DXGI_FORMAT                Format;
  UINT                       InputSlot;
  UINT                       AlignedByteOffset;
  D3D10_INPUT_CLASSIFICATION InputSlotClass;
  UINT                       InstanceDataStepRate;
} D3D10_INPUT_ELEMENT_DESC;</span>
Semant icName Semantic name is a string containing a word that describes the nature or purpose (or semantics) of this element. The word can be in any form that a C identifier can, and can be anything that we choose. For instance, a good semantic name for the vertex‘s position is POSITION. Semantic names are not case-sensitive.
SemanticIndex Semantic index supplements semantic name. A vertex may have multiple attributes of the same nature. For example, it may have 2 sets of texture coordinates or 2 sets of colors. Instead of using semantic names that have numbers appended, such as "COLOR0" and "COLOR1", the two elements can share a single semantic name, "COLOR", with different semantic indices 0 and 1.
Format Format defines the data type to be used for this element. For instance, a format of DXGI_FORMAT_R32G32B32_FLOAT has three 32-bit floating point numbers, making the element 12-byte long. A format of DXGI_FORMAT_R16G16B16A16_UINT has four 16-bit unsigned integers, making the element 8 bytes long.
InputSlot As mentioned previously, a Direct3D 10 application passes vertex data to the GPU via the use of vertex buffer. In Direct3D 10, multiple vertex buffers can be fed to the GPU simultaneously, 16 to be exact. Each vertex buffer is bound to an input slot number ranging from 0 to 15. The InputSlot field tells the GPU which vertex buffer it should fetch for this element.
AlignedByteOffset A vertex is stored in a vertex buffer, which is simply a chunk of memory. The AlignedByteOffset field tells the GPU the memory location to start fetching the data for this element.
InputSlotClass This field usually has the value D3D10_INPUT_PER_VERTEX_DATA. When an application uses instancing, it can set an input layout‘s InputSlotClass to D3D10_INPUT_PER_INSTANCE_DATA to work with vertex buffer containing instance data. Instancing is an advanced Direct3D topic and will not be discussed here. For ourtutorial, we will use D3D10_INPUT_PER_VERTEX_DATA exclusively. 
现在来定义D3D10_INPUT_ELEMENT_DESC并且创建输入布局：

// Define the input layout
D3D10_INPUT_ELEMENT_DESC layout[] =
{
    { L"POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D10_INPUT_PER_VERTEX_DATA, 0 },  
};
UINT numElements = sizeof(layout)/sizeof(layout[0]);

顶点布局：


// Create the input layout
D3D10_PASS_DESC PassDesc;
g_pTechnique->GetPassByIndex( 0 )->GetDesc( &PassDesc );
if( FAILED( g_pd3dDevice->CreateInputLayout( layout, numElements, PassDesc.pIAInputSignature, 
        PassDesc.IAInputSignatureSize, &g_pVertexLayout ) ) )
    return FALSE;
// Set the input layout
g_pd3dDevice->IASetInputLayout( g_pVertexLayout );

创建顶点缓存

 在初始化过程中另外一件需要完成的工作是为顶点数据创建存储的顶点缓存。在D3D10中创建一个顶点缓存需要填充2个结构体：D3D10_BUFFER_DESC以及D3D10_SUBRESOURSE_DATA,然后调用ID3D10device：：CreatBuffer（）函数。D3D10_BUFFER_DESC描述需要创建的顶点缓存对象，而D3D10_SUBRESOURCE_DATA则描述在创建顶点缓存是确切复制到顶点缓存内的值。

创建和初始化顶点缓存是一起立刻完成的，因此稍后我们不必再去初始化缓存。将要被复制到顶点缓存的是一系列的顶点：一个包含3个SimpleVertex结构体的数组。在这个顶点数组内的坐标系被选取因此我们可以发现一个使用我们着色器渲染的三角形出现在窗口程序的中间。当顶点缓存创建完毕后我们调用ID3D10Device：：IASetVertexBuffers（）函数来把它绑定到设备上去。全部代码如下：

// Create vertex buffer

//创建顶点缓存

SimpleVertex vertices[] =

{

    D3DXVECTOR3( 0.0f, 0.5f, 0.5f ),

    D3DXVECTOR3( 0.5f, -0.5f, 0.5f ),

    D3DXVECTOR3( -0.5f, -0.5f, 0.5f ),

};

D3D10_BUFFER_DESC bd;

bd.Usage = D3D10_USAGE_DEFAULT;

bd.ByteWidth = sizeof( SimpleVertex ) * 3;

bd.BindFlags = D3D10_BIND_VERTEX_BUFFER;

bd.CPUAccessFlags = 0;

bd.MiscFlags = 0;

D3D10_SUBRESOURCE_DATA InitData;

InitData.pSysMem = vertices;

if( FAILED( g_pd3dDevice->CreateBuffer( &bd, &InitData, &g_pVertexBuffer ) ) )

    return FALSE;

// Set vertex buffer

//设置顶点缓存

UINT stride = sizeof( SimpleVertex );

UINT offset = 0;

g_pd3dDevice->IASetVertexBuffers( 0, 1, &g_pVertexBuffer, &stride, &offset );


//--------------------------------------------------------------------------------------
// File: Tutorial02.cpp
//
// This application displays a triangle using Direct3D 10
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//--------------------------------------------------------------------------------------
#include <windows.h>
#include <d3d10.h>
#include <d3dx10.h>
#include "resource.h"


//--------------------------------------------------------------------------------------
// Structures
//--------------------------------------------------------------------------------------
struct SimpleVertex
{
    D3DXVECTOR3 Pos;
};


//--------------------------------------------------------------------------------------
// Global Variables
//--------------------------------------------------------------------------------------
HINSTANCE               g_hInst = NULL;
HWND                    g_hWnd = NULL;
D3D10_DRIVER_TYPE       g_driverType = D3D10_DRIVER_TYPE_NULL;
ID3D10Device*           g_pd3dDevice = NULL;
IDXGISwapChain*         g_pSwapChain = NULL;
ID3D10RenderTargetView* g_pRenderTargetView = NULL;
ID3D10Effect*           g_pEffect = NULL;
ID3D10EffectTechnique*  g_pTechnique = NULL;
ID3D10InputLayout*      g_pVertexLayout = NULL;
ID3D10Buffer*           g_pVertexBuffer = NULL;


//--------------------------------------------------------------------------------------
// Forward declarations
//--------------------------------------------------------------------------------------
HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow );
HRESULT InitDevice();
void CleanupDevice();
LRESULT CALLBACK    WndProc( HWND, UINT, WPARAM, LPARAM );
void Render();


//--------------------------------------------------------------------------------------
// Entry point to the program. Initializes everything and goes into a message processing 
// loop. Idle time is used to render the scene.
//--------------------------------------------------------------------------------------
int WINAPI wWinMain( HINSTANCE hInstance, HINSTANCE hPrevInstance, LPWSTR lpCmdLine, int nCmdShow )
{
    if( FAILED( InitWindow( hInstance, nCmdShow ) ) )
        return 0;

    if( FAILED( InitDevice() ) )
    {
        CleanupDevice();
        return 0;
    }

    // Main message loop
    MSG msg = {0};
    while( WM_QUIT != msg.message )
    {
        if( PeekMessage( &msg, NULL, 0, 0, PM_REMOVE ) )
        {
            TranslateMessage( &msg );
            DispatchMessage( &msg );
        }
        else
        {
            Render();
        }
    }

    CleanupDevice();

    return ( int )msg.wParam;
}


//--------------------------------------------------------------------------------------
// Register class and create window
//--------------------------------------------------------------------------------------
HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow )
{
    // Register class
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof( WNDCLASSEX );
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = hInstance;
    wcex.hIcon = LoadIcon( hInstance, ( LPCTSTR )IDI_TUTORIAL1 );
    wcex.hCursor = LoadCursor( NULL, IDC_ARROW );
    wcex.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );
    wcex.lpszMenuName = NULL;
    wcex.lpszClassName = L"TutorialWindowClass";
    wcex.hIconSm = LoadIcon( wcex.hInstance, ( LPCTSTR )IDI_TUTORIAL1 );
    if( !RegisterClassEx( &wcex ) )
        return E_FAIL;

    // Create window
    g_hInst = hInstance;
    RECT rc = { 0, 0, 640, 480 };
    AdjustWindowRect( &rc, WS_OVERLAPPEDWINDOW, FALSE );
    g_hWnd = CreateWindow( L"TutorialWindowClass", L"Direct3D 10 Tutorial 2: Rendering a Triangle",
                           WS_OVERLAPPEDWINDOW,
                           CW_USEDEFAULT, CW_USEDEFAULT, rc.right - rc.left, rc.bottom - rc.top, NULL, NULL, hInstance,
                           NULL );
    if( !g_hWnd )
        return E_FAIL;

    ShowWindow( g_hWnd, nCmdShow );

    return S_OK;
}


//--------------------------------------------------------------------------------------
// Create Direct3D device and swap chain
//--------------------------------------------------------------------------------------
HRESULT InitDevice()
{
    HRESULT hr = S_OK;

    RECT rc;
    GetClientRect( g_hWnd, &rc );
    UINT width = rc.right - rc.left;
    UINT height = rc.bottom - rc.top;

    UINT createDeviceFlags = 0;
#ifdef _DEBUG
    //createDeviceFlags |= D3D10_CREATE_DEVICE_DEBUG;
#endif

    D3D10_DRIVER_TYPE driverTypes[] =
    {
        D3D10_DRIVER_TYPE_HARDWARE,
        D3D10_DRIVER_TYPE_REFERENCE,
    };
    UINT numDriverTypes = sizeof( driverTypes ) / sizeof( driverTypes[0] );

    DXGI_SWAP_CHAIN_DESC sd;
    ZeroMemory( &sd, sizeof( sd ) );
    sd.BufferCount = 1;
    sd.BufferDesc.Width = width;
    sd.BufferDesc.Height = height;
    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    sd.BufferDesc.RefreshRate.Numerator = 60;
    sd.BufferDesc.RefreshRate.Denominator = 1;
    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    sd.OutputWindow = g_hWnd;
    sd.SampleDesc.Count = 1;
    sd.SampleDesc.Quality = 0;
    sd.Windowed = TRUE;

    for( UINT driverTypeIndex = 0; driverTypeIndex < numDriverTypes; driverTypeIndex++ )
    {
        g_driverType = driverTypes[driverTypeIndex];
        hr = D3D10CreateDeviceAndSwapChain( NULL, g_driverType, NULL, createDeviceFlags,
                                            D3D10_SDK_VERSION, &sd, &g_pSwapChain, &g_pd3dDevice );
        if( SUCCEEDED( hr ) )
            break;
    }
    if( FAILED( hr ) )
        return hr;

    // Create a render target view
    ID3D10Texture2D* pBuffer;
    hr = g_pSwapChain->GetBuffer( 0, __uuidof( ID3D10Texture2D ), ( LPVOID* )&pBuffer );
    if( FAILED( hr ) )
        return hr;

    hr = g_pd3dDevice->CreateRenderTargetView( pBuffer, NULL, &g_pRenderTargetView );
    pBuffer->Release();
    if( FAILED( hr ) )
        return hr;

    g_pd3dDevice->OMSetRenderTargets( 1, &g_pRenderTargetView, NULL );

    // Setup the viewport
    D3D10_VIEWPORT vp;
    vp.Width = width;
    vp.Height = height;
    vp.MinDepth = 0.0f;
    vp.MaxDepth = 1.0f;
    vp.TopLeftX = 0;
    vp.TopLeftY = 0;
    g_pd3dDevice->RSSetViewports( 1, &vp );

    // Create the effect
    DWORD dwShaderFlags = D3D10_SHADER_ENABLE_STRICTNESS;
#if defined( DEBUG ) || defined( _DEBUG )
    // Set the D3D10_SHADER_DEBUG flag to embed debug information in the shaders.
    // Setting this flag improves the shader debugging experience, but still allows 
    // the shaders to be optimized and to run exactly the way they will run in 
    // the release configuration of this program.
    dwShaderFlags |= D3D10_SHADER_DEBUG;
    #endif
    hr = D3DX10CreateEffectFromFile( L"Tutorial02.fx", NULL, NULL, "fx_4_0", dwShaderFlags, 0,
                                         g_pd3dDevice, NULL, NULL, &g_pEffect, NULL, NULL );
    if( FAILED( hr ) )
    {
        MessageBox( NULL,
                    L"The FX file cannot be located.  Please run this executable from the directory that contains the FX file.", L"Error", MB_OK );
        return hr;
    }

    // Obtain the technique
    g_pTechnique = g_pEffect->GetTechniqueByName( "Render" );

    // Define the input layout
    D3D10_INPUT_ELEMENT_DESC layout[] =
    {
        { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D10_INPUT_PER_VERTEX_DATA, 0 },
    };
    UINT numElements = sizeof( layout ) / sizeof( layout[0] );

    // Create the input layout
    D3D10_PASS_DESC PassDesc;
    g_pTechnique->GetPassByIndex( 0 )->GetDesc( &PassDesc );
    hr = g_pd3dDevice->CreateInputLayout( layout, numElements, PassDesc.pIAInputSignature,
                                          PassDesc.IAInputSignatureSize, &g_pVertexLayout );
    if( FAILED( hr ) )
        return hr;

    // Set the input layout
    g_pd3dDevice->IASetInputLayout( g_pVertexLayout );

    // Create vertex buffer
    SimpleVertex vertices[] =
    {
        D3DXVECTOR3( 0.0f, 0.5f, 0.5f ),
        D3DXVECTOR3( 0.5f, -0.5f, 0.5f ),
        D3DXVECTOR3( -0.5f, -0.5f, 0.5f ),
    };
    D3D10_BUFFER_DESC bd;
    bd.Usage = D3D10_USAGE_DEFAULT;
    bd.ByteWidth = sizeof( SimpleVertex ) * 3;
    bd.BindFlags = D3D10_BIND_VERTEX_BUFFER;
    bd.CPUAccessFlags = 0;
    bd.MiscFlags = 0;
    D3D10_SUBRESOURCE_DATA InitData;
    InitData.pSysMem = vertices;
    hr = g_pd3dDevice->CreateBuffer( &bd, &InitData, &g_pVertexBuffer );
    if( FAILED( hr ) )
        return hr;

    // Set vertex buffer
    UINT stride = sizeof( SimpleVertex );
    UINT offset = 0;
    g_pd3dDevice->IASetVertexBuffers( 0, 1, &g_pVertexBuffer, &stride, &offset );

    // Set primitive topology
    g_pd3dDevice->IASetPrimitiveTopology( D3D10_PRIMITIVE_TOPOLOGY_TRIANGLELIST );

    return S_OK;
}


//--------------------------------------------------------------------------------------
// Clean up the objects we've created
//--------------------------------------------------------------------------------------
void CleanupDevice()
{
    if( g_pd3dDevice ) g_pd3dDevice->ClearState();

    if( g_pVertexBuffer ) g_pVertexBuffer->Release();
    if( g_pVertexLayout ) g_pVertexLayout->Release();
    if( g_pEffect ) g_pEffect->Release();
    if( g_pRenderTargetView ) g_pRenderTargetView->Release();
    if( g_pSwapChain ) g_pSwapChain->Release();
    if( g_pd3dDevice ) g_pd3dDevice->Release();
}


//--------------------------------------------------------------------------------------
// Called every time the application receives a message
//--------------------------------------------------------------------------------------
LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam )
{
    PAINTSTRUCT ps;
    HDC hdc;

    switch( message )
    {
        case WM_PAINT:
            hdc = BeginPaint( hWnd, &ps );
            EndPaint( hWnd, &ps );
            break;

        case WM_DESTROY:
            PostQuitMessage( 0 );
            break;

        default:
            return DefWindowProc( hWnd, message, wParam, lParam );
    }

    return 0;
}


//--------------------------------------------------------------------------------------
// Render a frame
//--------------------------------------------------------------------------------------
void Render()
{
    // Clear the back buffer 
    float ClearColor[4] = { 0.0f, 0.125f, 0.3f, 1.0f }; // red,green,blue,alpha
    g_pd3dDevice->ClearRenderTargetView( g_pRenderTargetView, ClearColor );

    // Render a triangle
    D3D10_TECHNIQUE_DESC techDesc;
    g_pTechnique->GetDesc( &techDesc );
    for( UINT p = 0; p < techDesc.Passes; ++p )
    {
        g_pTechnique->GetPassByIndex( p )->Apply( 0 );
        g_pd3dDevice->Draw( 3, 0 );
    }

    // Present the information rendered to the back buffer to the front buffer (the screen)
    g_pSwapChain->Present( 0, 0 );
}













directx学习之在屏幕上画一个三角形


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