06.索引

介绍

本课程直接基于上一课程。我们将学习如何使用索引。索引列表通常是三角形的列表。它们对于绘制几何图形非常有用，并且可以保持顶点计数不变。当我们开始加载模型时，它也非常有用。

指标

如果要绘制一个正方形，而没有索引缓冲区，则需要绘制两个三角形。每个三角形将包含3个顶点，因此顶点缓冲区如下所示：{v0，v1，v2，v3，v4，v5}，其中三角形1由v0，v1，v2定义，三角形2由v3定义，v4，v5。 现在，考虑一个包含数千个三角形的巨大模型，以及您必须制作多少个重复的顶点。使用索引列表定义三角形，我们的顶点缓冲区应类似于：{v0，v1，v2，v3}，其中三角形1由v0，v1，v2定义，三角形2由v0，v2，v3定义。

全球宣言

由于我们在上一课中已经介绍了ID3D11Buffer，因此在此不再赘述。但是正如您所看到的，我们创建了一个新的缓冲区来保存我们的平方索引列表。您还可以看到我们将顶点缓冲区的名称更改为正方形而不是三角形。

ID3D11Buffer* squareIndexBuffer;
ID3D11Buffer* squareVertBuffer;

顶点列表

我们将“顶点”列表修改为看起来像正方形，并添加了一个顶点。这里没有太多要说的。

Vertex v[] =
{
    Vertex( -0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f ),
    Vertex( -0.5f,  0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f ),
    Vertex(  0.5f,  0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f ),
    Vertex(  0.5f, -0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f ),
};

索引缓冲区

这是我们将创建索引缓冲区的地方。首先创建一个DWORD数组来定义两个三角形。然后，我们初始化并填写一个D3D11_BUFFER_DESC对象，该对象将定义索引缓冲区。您可以看到字节宽度是DWORD的大小乘以2乘以3。这是因为索引数组中的每个元素都是DWORD类型，因此我们需要获取DWORD类型的大小，再乘以面数（或三角形），然后将其乘以3，因为每个三角形包含3个顶点或索引数组中的元素。之后，我们将绑定标志设置为D3D11_BIND_INDEX_BUFFER。这将告诉管道的IA阶段这是一个索引缓冲区。

DWORD indices[] = {
    0, 1, 2,
    0, 2, 3,
};

D3D11_BUFFER_DESC indexBufferDesc;
ZeroMemory( &indexBufferDesc, sizeof(indexBufferDesc) );

indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
indexBufferDesc.ByteWidth = sizeof(DWORD) * 2 * 3;
indexBufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
indexBufferDesc.CPUAccessFlags = 0;
indexBufferDesc.MiscFlags = 0;

接下来，我们将索引数组放入D3D11_SUBRESOURCE_DATA，通过调用D3D11DeviceContext :: CreateBuffer（）创建缓冲区，然后通过调用函数D3D11DeviceContext :: IASetIndexBuffer（）将缓冲区绑定到管道的IA阶段。第一个参数是创建的索引缓冲区，第二个参数是格式。我们指定DXGI_FORMAT_R32_UINT，这是一个简单的32位浮点数，但是我们也可以为16位浮点数指定DXGI_FORMAT_R16_UINT。最后一个参数是偏移量，它是在索引数组中使用的第一个索引。也许您的索引缓冲区定义了多个对象，但是您只想绘制一个。在绘制对象之前，可以将索引缓冲区与该对象的起始偏移量绑定。

D3D11_SUBRESOURCE_DATA iinitData;

iinitData.pSysMem = indices;
d3d11Device->CreateBuffer(&indexBufferDesc, &iinitData, &squareIndexBuffer);

d3d11DevCon->IASetIndexBuffer( squareIndexBuffer, DXGI_FORMAT_R32_UINT, 0);

索引缓冲区

由于我们在顶点数组中添加了另一个顶点，因此我们需要将缓冲区更新为4个顶点的大小，而不是最后一个顶点的3个。

vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
vertexBufferDesc.ByteWidth = sizeof( Vertex ) * 4;
vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
vertexBufferDesc.CPUAccessFlags = 0;
vertexBufferDesc.MiscFlags = 0;

不要忘记释放COM对象！

void CleanUp()
{
    //Release the COM Objects we created
    SwapChain->Release();
    d3d11Device->Release();
    d3d11DevCon->Release();
    renderTargetView->Release();
    squareVertBuffer->Release();
    squareIndexBuffer->Release();
    VS->Release();
    PS->Release();
    VS_Buffer->Release();
    PS_Buffer->Release();
    vertLayout->Release();
}

索引缓冲区

最后我们画出正方形。我们可以通过调用D3D11DeviceContext :: DrawIndexed（）方法来绘制索引基元。第一个参数是要绘制的索引数，第二个参数是从索引缓冲区开始到开始绘制的偏移量。如果我们只想绘制第二个三角形，则可以在此处指定“ 4”。第三个参数可能有些混乱，也许不是。这是从顶点缓冲区开始到开始绘制的偏移量。您可能有两个索引缓冲区，一个描述一个球体，一个描述一个盒子。但是，也许两者都在一个顶点缓冲区中，其中球体是顶点缓冲区中的第一组顶点，而框是第二组。因此，要绘制框，您需要将第三个参数设置为球体中的顶点数，

void DrawScene()
{
    //Clear our backbuffer
    float bgColor[4] = {(0.0f, 0.0f, 0.0f, 0.0f)};
    d3d11DevCon->ClearRenderTargetView(renderTargetView, bgColor);

    //Draw the triangle
    d3d11DevCon->DrawIndexed( 6, 0, 0 );

    //Present the backbuffer to the screen
    SwapChain->Present(0, 0);
}

现在我们完成了索引课程！

行使：

1.制作两个索引缓冲区。一个保持一个三角形，另一个保持两个三角形。将所有顶点放入一个缓冲区中，并仅在顶点缓冲区中绘制后两个三角形。提示->>（DrawIndexed方法的第三个参数）

2.执行与第一个练习中相同的操作，但不要有两个索引缓冲区，而要创建两个顶点缓冲区和一个索引缓冲区。提示->>（DrawIndexed方法的第二个参数）

这是最终的代码：

main.cpp

//Include and link appropriate libraries and headers//
#pragma comment(lib, "d3d11.lib")
#pragma comment(lib, "d3dx11.lib")
#pragma comment(lib, "d3dx10.lib")

#include <windows.h>
#include <d3d11.h>
#include <d3dx11.h>
#include <d3dx10.h>
#include <xnamath.h>

//Global Declarations - Interfaces//
IDXGISwapChain* SwapChain;
ID3D11Device* d3d11Device;
ID3D11DeviceContext* d3d11DevCon;
ID3D11RenderTargetView* renderTargetView;
///**************new**************
ID3D11Buffer* squareIndexBuffer;
ID3D11Buffer* squareVertBuffer;
///**************new**************
ID3D11VertexShader* VS;
ID3D11PixelShader* PS;
ID3D10Blob* VS_Buffer;
ID3D10Blob* PS_Buffer;
ID3D11InputLayout* vertLayout;

//Global Declarations - Others//
LPCTSTR WndClassName = L"firstwindow";
HWND hwnd = NULL;
HRESULT hr;

const int Width  = 300;
const int Height = 300;

//Function Prototypes//
bool InitializeDirect3d11App(HINSTANCE hInstance);
void CleanUp();
bool InitScene();
void UpdateScene();
void DrawScene();

bool InitializeWindow(HINSTANCE hInstance,
    int ShowWnd,
    int width, int height,
    bool windowed);
int messageloop();

LRESULT CALLBACK WndProc(HWND hWnd,
    UINT msg,
    WPARAM wParam,
    LPARAM lParam);

//Vertex Structure and Vertex Layout (Input Layout)//
struct Vertex    //Overloaded Vertex Structure
{
    Vertex(){}
    Vertex(float x, float y, float z,
        float cr, float cg, float cb, float ca)
        : pos(x,y,z), color(cr, cg, cb, ca){}

    XMFLOAT3 pos;
    XMFLOAT4 color;
};

D3D11_INPUT_ELEMENT_DESC layout[] =
{
    { "POSITION", 0, DXGI_FORMAT_R32G32B32_FLOAT, 0, 0, D3D11_INPUT_PER_VERTEX_DATA, 0 },  
    { "COLOR", 0, DXGI_FORMAT_R32G32B32A32_FLOAT, 0, 12, D3D11_INPUT_PER_VERTEX_DATA, 0 },  
};
UINT numElements = ARRAYSIZE(layout);

int WINAPI WinMain(HINSTANCE hInstance,    //Main windows function
    HINSTANCE hPrevInstance, 
    LPSTR lpCmdLine,
    int nShowCmd)
{

    if(!InitializeWindow(hInstance, nShowCmd, Width, Height, true))
    {
        MessageBox(0, L"Window Initialization - Failed",
            L"Error", MB_OK);
        return 0;
    }

    if(!InitializeDirect3d11App(hInstance))    //Initialize Direct3D
    {
        MessageBox(0, L"Direct3D Initialization - Failed",
            L"Error", MB_OK);
        return 0;
    }

    if(!InitScene())    //Initialize our scene
    {
        MessageBox(0, L"Scene Initialization - Failed",
            L"Error", MB_OK);
        return 0;
    }

    messageloop();

    CleanUp();    

    return 0;
}

bool InitializeWindow(HINSTANCE hInstance,
    int ShowWnd,
    int width, int height,
    bool windowed)
{
    typedef struct _WNDCLASS {
        UINT cbSize;
        UINT style;
        WNDPROC lpfnWndProc;
        int cbClsExtra;
        int cbWndExtra;
        HANDLE hInstance;
        HICON hIcon;
        HCURSOR hCursor;
        HBRUSH hbrBackground;
        LPCTSTR lpszMenuName;
        LPCTSTR lpszClassName;
    } WNDCLASS;

    WNDCLASSEX wc;

    wc.cbSize = sizeof(WNDCLASSEX);
    wc.style = CS_HREDRAW | CS_VREDRAW;
    wc.lpfnWndProc = WndProc;
    wc.cbClsExtra = NULL;
    wc.cbWndExtra = NULL;
    wc.hInstance = hInstance;
    wc.hIcon = LoadIcon(NULL, IDI_APPLICATION);
    wc.hCursor = LoadCursor(NULL, IDC_ARROW);
    wc.hbrBackground = (HBRUSH)(COLOR_WINDOW + 2);
    wc.lpszMenuName = NULL;
    wc.lpszClassName = WndClassName;
    wc.hIconSm = LoadIcon(NULL, IDI_APPLICATION);

    if (!RegisterClassEx(&wc))
    {
        MessageBox(NULL, L"Error registering class",    
            L"Error", MB_OK | MB_ICONERROR);
        return 1;
    }

    hwnd = CreateWindowEx(
        NULL,
        WndClassName,
        L"Lesson 4 - Begin Drawing",
        WS_OVERLAPPEDWINDOW,
        CW_USEDEFAULT, CW_USEDEFAULT,
        width, height,
        NULL,
        NULL,
        hInstance,
        NULL
        );

    if (!hwnd)
    {
        MessageBox(NULL, L"Error creating window",
            L"Error", MB_OK | MB_ICONERROR);
        return 1;
    }

    ShowWindow(hwnd, ShowWnd);
    UpdateWindow(hwnd);

    return true;
}

bool InitializeDirect3d11App(HINSTANCE hInstance)
{
    //Describe our Buffer
    DXGI_MODE_DESC bufferDesc;

    ZeroMemory(&bufferDesc, sizeof(DXGI_MODE_DESC));

    bufferDesc.Width = Width;
    bufferDesc.Height = Height;
    bufferDesc.RefreshRate.Numerator = 60;
    bufferDesc.RefreshRate.Denominator = 1;
    bufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    bufferDesc.ScanlineOrdering = DXGI_MODE_SCANLINE_ORDER_UNSPECIFIED;
    bufferDesc.Scaling = DXGI_MODE_SCALING_UNSPECIFIED;

    //Describe our SwapChain
    DXGI_SWAP_CHAIN_DESC swapChainDesc; 

    ZeroMemory(&swapChainDesc, sizeof(DXGI_SWAP_CHAIN_DESC));

    swapChainDesc.BufferDesc = bufferDesc;
    swapChainDesc.SampleDesc.Count = 1;
    swapChainDesc.SampleDesc.Quality = 0;
    swapChainDesc.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    swapChainDesc.BufferCount = 1;
    swapChainDesc.OutputWindow = hwnd; 
    swapChainDesc.Windowed = TRUE; 
    swapChainDesc.SwapEffect = DXGI_SWAP_EFFECT_DISCARD;


    //Create our SwapChain
    hr = D3D11CreateDeviceAndSwapChain(NULL, D3D_DRIVER_TYPE_HARDWARE, NULL, NULL, NULL, NULL,
        D3D11_SDK_VERSION, &swapChainDesc, &SwapChain, &d3d11Device, NULL, &d3d11DevCon);

    //Create our BackBuffer
    ID3D11Texture2D* BackBuffer;
    hr = SwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), (void**)&BackBuffer );

    //Create our Render Target
    hr = d3d11Device->CreateRenderTargetView( BackBuffer, NULL, &renderTargetView );
    BackBuffer->Release();

    //Set our Render Target
    d3d11DevCon->OMSetRenderTargets( 1, &renderTargetView, NULL );

    return true;
}

void CleanUp()
{
    //Release the COM Objects we created
    SwapChain->Release();
    d3d11Device->Release();
    d3d11DevCon->Release();
    renderTargetView->Release();
    ///**************new**************
    squareVertBuffer->Release();
    squareIndexBuffer->Release();
    ///**************new**************
    VS->Release();
    PS->Release();
    VS_Buffer->Release();
    PS_Buffer->Release();
    vertLayout->Release();
}

bool InitScene()
{
    //Compile Shaders from shader file
    hr = D3DX11CompileFromFile(L"Effects.fx", 0, 0, "VS", "vs_4_0", 0, 0, 0, &VS_Buffer, 0, 0);
    hr = D3DX11CompileFromFile(L"Effects.fx", 0, 0, "PS", "ps_4_0", 0, 0, 0, &PS_Buffer, 0, 0);

    //Create the Shader Objects
    hr = d3d11Device->CreateVertexShader(VS_Buffer->GetBufferPointer(), VS_Buffer->GetBufferSize(), NULL, &VS);
    hr = d3d11Device->CreatePixelShader(PS_Buffer->GetBufferPointer(), PS_Buffer->GetBufferSize(), NULL, &PS);

    //Set Vertex and Pixel Shaders
    d3d11DevCon->VSSetShader(VS, 0, 0);
    d3d11DevCon->PSSetShader(PS, 0, 0);

    ///**************new**************
    //Create the vertex buffer
    Vertex v[] =
    {
        Vertex( -0.5f, -0.5f, 0.5f, 1.0f, 0.0f, 0.0f, 1.0f ),
        Vertex( -0.5f,  0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f ),
        Vertex(  0.5f,  0.5f, 0.5f, 0.0f, 0.0f, 1.0f, 1.0f ),
        Vertex(  0.5f, -0.5f, 0.5f, 0.0f, 1.0f, 0.0f, 1.0f ),
    };

    DWORD indices[] = {
        0, 1, 2,
        0, 2, 3,
    };

    D3D11_BUFFER_DESC indexBufferDesc;
    ZeroMemory( &indexBufferDesc, sizeof(indexBufferDesc) );

    indexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
    indexBufferDesc.ByteWidth = sizeof(DWORD) * 2 * 3;
    indexBufferDesc.BindFlags = D3D11_BIND_INDEX_BUFFER;
    indexBufferDesc.CPUAccessFlags = 0;
    indexBufferDesc.MiscFlags = 0;

    D3D11_SUBRESOURCE_DATA iinitData;

    iinitData.pSysMem = indices;
    d3d11Device->CreateBuffer(&indexBufferDesc, &iinitData, &squareIndexBuffer);

    d3d11DevCon->IASetIndexBuffer( squareIndexBuffer, DXGI_FORMAT_R32_UINT, 0);

    D3D11_BUFFER_DESC vertexBufferDesc;
    ZeroMemory( &vertexBufferDesc, sizeof(vertexBufferDesc) );

    vertexBufferDesc.Usage = D3D11_USAGE_DEFAULT;
    vertexBufferDesc.ByteWidth = sizeof( Vertex ) * 4;
    vertexBufferDesc.BindFlags = D3D11_BIND_VERTEX_BUFFER;
    vertexBufferDesc.CPUAccessFlags = 0;
    vertexBufferDesc.MiscFlags = 0;

    D3D11_SUBRESOURCE_DATA vertexBufferData; 

    ZeroMemory( &vertexBufferData, sizeof(vertexBufferData) );
    vertexBufferData.pSysMem = v;
    hr = d3d11Device->CreateBuffer( &vertexBufferDesc, &vertexBufferData, &squareVertBuffer);
    ///**************new**************

    //Set the vertex buffer
    UINT stride = sizeof( Vertex );
    UINT offset = 0;
    d3d11DevCon->IASetVertexBuffers( 0, 1, &squareVertBuffer, &stride, &offset );

    //Create the Input Layout
    hr = d3d11Device->CreateInputLayout( layout, numElements, VS_Buffer->GetBufferPointer(), 
        VS_Buffer->GetBufferSize(), &vertLayout );

    //Set the Input Layout
    d3d11DevCon->IASetInputLayout( vertLayout );

    //Set Primitive Topology
    d3d11DevCon->IASetPrimitiveTopology( D3D11_PRIMITIVE_TOPOLOGY_TRIANGLELIST );

    //Create the Viewport
    D3D11_VIEWPORT viewport;
    ZeroMemory(&viewport, sizeof(D3D11_VIEWPORT));

    viewport.TopLeftX = 0;
    viewport.TopLeftY = 0;
    viewport.Width = Width;
    viewport.Height = Height;

    //Set the Viewport
    d3d11DevCon->RSSetViewports(1, &viewport);

    return true;
}

void UpdateScene()
{

}

void DrawScene()
{
    //Clear our backbuffer
    float bgColor[4] = {(0.0f, 0.0f, 0.0f, 0.0f)};
    d3d11DevCon->ClearRenderTargetView(renderTargetView, bgColor);

    ///**************new**************
    //Draw the triangle
    d3d11DevCon->DrawIndexed( 6, 0, 0 );
    ///**************new**************

    //Present the backbuffer to the screen
    SwapChain->Present(0, 0);
}

int messageloop(){
    MSG msg;
    ZeroMemory(&msg, sizeof(MSG));
    while(true)
    {
        BOOL PeekMessageL( 
            LPMSG lpMsg,
            HWND hWnd,
            UINT wMsgFilterMin,
            UINT wMsgFilterMax,
            UINT wRemoveMsg
            );

        if (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
        {
            if (msg.message == WM_QUIT)
                break;
            TranslateMessage(&msg);    
            DispatchMessage(&msg);
        }
        else{
            // run game code            
            UpdateScene();
            DrawScene();
        }
    }
    return msg.wParam;
}

LRESULT CALLBACK WndProc(HWND hwnd,
    UINT msg,
    WPARAM wParam,
    LPARAM lParam)
{
    switch( msg )
    {
    case WM_KEYDOWN:
        if( wParam == VK_ESCAPE ){
            DestroyWindow(hwnd);
        }
        return 0;

    case WM_DESTROY:
        PostQuitMessage(0);
        return 0;
    }
    return DefWindowProc(hwnd,
        msg,
        wParam,
        lParam);
}

效果器

struct VS_OUTPUT
{
    float4 Pos : SV_POSITION;
    float4 Color : COLOR;
};

VS_OUTPUT VS(float4 inPos : POSITION, float4 inColor : COLOR)
{
    VS_OUTPUT output;

    output.Pos = inPos;
    output.Color = inColor;

    return output;
}

float4 PS(VS_OUTPUT input) : SV_TARGET
{
    return input.Color;
}