DirectX 9.0 C++ 教程 关于Perspective projection,Matrices,摄像头，旋转

效果图：

对上面这张gif图片是如何制作感兴趣？看截取视频，然后制成gif 教程

1.坐标系

  默认情况下，Direct3D使用的是左手坐标系。这意味着虚拟3D网格上的每个正坐标远离观察者的方向。例如，Z轴的正坐标是冲向屏幕里面的，Y轴的正坐标是向上的，而X轴的正坐标是向右的。这里提下OpenGL使用的是右手坐标系，Z轴的正坐标是冲向屏幕外面的。X轴和Y轴是一样的。

2.先介绍下Projection,即投射

投射主要分下面的两种。
1.透视投射 （perspective projection） ，远处的物体会小些，像我们现实中眼睛看到的样子

2.平行投射（parallel projection） 不管物体离摄像机多远，物体大小不变，一般用在2D编程

在我们程序中不仅要规定摄像头的位置(就是上图中眼睛的位置)，还要规定摄像头看的范围，如果物体在范围之外，会被切割掉。中文叫视锥体，就是下图中阴影部分。看图我们发现要定义3个东西，fovy(用角度)，near(到摄像头的最近距离)，far(到摄像头最远的距离)，还有个纵横比(aspect radio)。

//D3DXMatrixPerspectiveFovLH函数原型
D3DXMATRIX *WINAPI D3DXMatrixPerspectiveFovLH(          
  D3DXMATRIX *pOut,//操作结果
    FLOAT fovy,    //在y轴上的度数
    FLOAT Aspect,  //纵横比
    FLOAT zn,     // near
    FLOAT zf      //far
);
//例子，注意度数这里D3DX_PI表示180度。
D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 640/480, 1.0f, 100.0f );
 

3.接下来是Camera(摄像头)的位置

//D3DXMatrixLookAtLH函数原型。
D3DXMATRIX *WINAPI D3DXMatrixLookAtLH(          
    D3DXMATRIX *pOut, //操作结果
    CONST D3DXVECTOR3 *pEye,//摄像头的位置
    CONST D3DXVECTOR3 *pAt, //摄像头对准看的位置
 CONST D3DXVECTOR3 *pUp   //规定哪个坐标朝上，一般Y轴朝上,用(0.0f,1.0f,0.0f)
);
//具体例子
D3DXVECTOR3 vEyePt(0.0f, 0.0f,-5.0f );
    D3DXVECTOR3 vLookatPt( 0.0f, 3.0f, 0.0f );
    D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f );
    D3DXMATRIXA16 matView;
    D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
    g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView ); 

4.DirectX中的旋转

UINT  iTime  = timeGetTime() % 1000;//会产生[0-1000]的数字
    FLOAT fAngle = iTime * (2.0f * D3DX_PI) / 1000.0f; //这里度数就是 [0-1] * 360度。
    D3DXMatrixRotationY( &matWorld, fAngle ); //这里是绕y轴旋转，同理绕x轴旋转就是调用D3DXMatrixRotationX
    g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );

5.完整代码

//-----------------------------------------------------------------------------
// File: Matrices.cpp
//
// Desc: Now that we know how to create a device and render some 2D vertices,
//       this tutorial goes the next step and renders 3D geometry. To deal with
//       3D geometry we need to introduce the use of 4x4 Matrices to transform
//       the geometry with translations, rotations, scaling, and setting up our
//       camera.
//
//       Geometry is defined in model space. We can move it (translation),
//       rotate it (rotation), or stretch it (scaling) using a world transform.
//       The geometry is then said to be in world space. Next, we need to
//       position the camera, or eye point, somewhere to look at the geometry.
//       Another transform, via the view matrix, is used, to position and
//       rotate our view. With the geometry then in view space, our last
//       transform is the projection transform, which "projects" the 3D scene
//       into our 2D viewport.
//
//       Note that in this tutorial, we are introducing the use of D3DX, which
//       is a set of helper utilities for D3D. In this case, we are using some
//       of D3DX's useful matrix initialization functions. To use D3DX, simply
//       include <d3dx9.h> and link with d3dx9.lib.
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
#include <Windows.h>
#include <mmsystem.h>
#include <d3dx9.h>
#include <strsafe.h>




//-----------------------------------------------------------------------------
// Global variables
//-----------------------------------------------------------------------------
LPDIRECT3D9             g_pD3D       = NULL; // Used to create the D3DDevice
LPDIRECT3DDEVICE9       g_pd3dDevice = NULL; // Our rendering device
LPDIRECT3DVERTEXBUFFER9 g_pVB        = NULL; // Buffer to hold Vertices

// A structure for our custom vertex type
struct CUSTOMVERTEX
{
    FLOAT x, y, z; // The transformed position for the vertex
    DWORD color;        // The vertex color
};

// Our custom FVF, which describes our custom vertex structure
#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZ|D3DFVF_DIFFUSE)
//#define D3DFVF_CUSTOMVERTEX (D3DFVF_XYZRHW)




//-----------------------------------------------------------------------------
// Name: InitD3D()
// Desc: Initializes Direct3D
//-----------------------------------------------------------------------------
HRESULT InitD3D( HWND hWnd )
{
    // Create the D3D object.
    if( NULL == ( g_pD3D = Direct3DCreate9( D3D_SDK_VERSION ) ) )
        return E_FAIL;

    // Set up the structure used to create the D3DDevice
    D3DPRESENT_PARAMETERS d3dpp;
    ZeroMemory( &d3dpp, sizeof(d3dpp) );
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
    d3dpp.BackBufferFormat = D3DFMT_UNKNOWN;

    // Create the D3DDevice
    if( FAILED( g_pD3D->CreateDevice( D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd,
                                      D3DCREATE_SOFTWARE_VERTEXPROCESSING,
                                      &d3dpp, &g_pd3dDevice ) ) )
    {
        return E_FAIL;
    }

    // Turn off culling, so we see the front and back of the triangle
    g_pd3dDevice->SetRenderState( D3DRS_CULLMODE, D3DCULL_NONE );

    // Turn off D3D lighting, since we are providing our own vertex colors
    g_pd3dDevice->SetRenderState( D3DRS_LIGHTING, FALSE );

    return S_OK;
}




//-----------------------------------------------------------------------------
// Name: InitVB()
// Desc: Creates a vertex buffer and fills it with our Vertices. The vertex
//       buffer is basically just a chuck of memory that holds Vertices. After
//       creating it, we must Lock()/Unlock() it to fill it. For indices, D3D
//       also uses index buffers. The special thing about vertex and index
//       buffers is that they can be created in device memory, allowing some
//       cards to process them in hardware, resulting in a dramatic
//       performance gain.
//-----------------------------------------------------------------------------
HRESULT InitVB()
{
    // 因为是矩形，所以要定义4个点
    CUSTOMVERTEX Vertices[] =
    {
        { -1.0f, -1.0f, 0.0f, D3DCOLOR_XRGB(0,255,255), }, // x, y, z, rhw, color
        { -1.0f, 1.0f, 0.0f, D3DCOLOR_XRGB(255,0,0), },
        { 1.0f, -1.0f, 0.0f, D3DCOLOR_XRGB(0,255,0), },
		{ 1.0f, 1.0f, 0.0f, D3DCOLOR_XRGB(0,0,255), },
    };

    // Create the vertex buffer. Here we are allocating enough memory
    // (from the default pool) to hold all our 3 custom Vertices. We also
    // specify the FVF, so the vertex buffer knows what data it contains.
    if( FAILED( g_pd3dDevice->CreateVertexBuffer( sizeof(Vertices),
                                                  0, D3DFVF_CUSTOMVERTEX,
                                                  D3DPOOL_DEFAULT, &g_pVB, NULL ) ) )
    {
        return E_FAIL;
    }

    // Now we fill the vertex buffer. To do this, we need to Lock() the VB to
    // gain access to the Vertices. This mechanism is required becuase vertex
    // buffers may be in device memory.
    VOID* pVertices;
    if( FAILED( g_pVB->Lock( 0, sizeof(Vertices), (void**)&pVertices, 0 ) ) )
        return E_FAIL;
    memcpy( pVertices, Vertices, sizeof(Vertices) );
    g_pVB->Unlock();

    return S_OK;
}




//-----------------------------------------------------------------------------
// Name: Cleanup()
// Desc: Releases all previously initialized objects
//-----------------------------------------------------------------------------
VOID Cleanup()
{
    if( g_pVB != NULL )        
        g_pVB->Release();

    if( g_pd3dDevice != NULL ) 
        g_pd3dDevice->Release();

    if( g_pD3D != NULL )       
        g_pD3D->Release();
}


//-----------------------------------------------------------------------------
// Name: SetupMatrices()
// Desc: Sets up the world, view, and projection transform Matrices.
//-----------------------------------------------------------------------------
VOID SetupMatrices()
{
    // For our world matrix, we will just rotate the object about the y-axis.
    D3DXMATRIXA16 matWorld;
	
    // 根据时间，改变角度旋转
    UINT  iTime  = timeGetTime() % 1000;
    FLOAT fAngle = iTime * (2.0f * D3DX_PI) / 1000.0f;
    D3DXMatrixRotationY( &matWorld, fAngle);
    g_pd3dDevice->SetTransform( D3DTS_WORLD, &matWorld );
	
    // 定义摄像头的位置
    D3DXVECTOR3 vEyePt(0.0f, 3.0f,-5.0f );
    D3DXVECTOR3 vLookatPt( 0.0f, 0.0f, 0.0f );
    D3DXVECTOR3 vUpVec( 0.0f, 1.0f, 0.0f );
    D3DXMATRIXA16 matView;
    D3DXMatrixLookAtLH( &matView, &vEyePt, &vLookatPt, &vUpVec );
    g_pd3dDevice->SetTransform( D3DTS_VIEW, &matView );
	
    // 定义视锥体的大小
    D3DXMATRIXA16 matProj;
    D3DXMatrixPerspectiveFovLH( &matProj, D3DX_PI/4, 640/480, 1.0f, 100.0f );
    g_pd3dDevice->SetTransform( D3DTS_PROJECTION, &matProj );
}

//-----------------------------------------------------------------------------
// Name: Render()
// Desc: Draws the scene
//-----------------------------------------------------------------------------
VOID Render()
{
    // 黑色
    g_pd3dDevice->Clear( 0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0,0,0), 1.0f, 0 );

    // Begin the scene
    if( SUCCEEDED( g_pd3dDevice->BeginScene() ) )
    {
        // Setup the world, view, and projection Matrices
        SetupMatrices();

        // Render the vertex buffer contents
        g_pd3dDevice->SetStreamSource( 0, g_pVB, 0, sizeof(CUSTOMVERTEX) );
        g_pd3dDevice->SetFVF( D3DFVF_CUSTOMVERTEX );
        g_pd3dDevice->DrawPrimitive( D3DPT_TRIANGLESTRIP, 0, 2 );//因为是矩形，所以是由两个三角形组成

        // End the scene
        g_pd3dDevice->EndScene();
    }

    // Present the backbuffer contents to the display
    g_pd3dDevice->Present( NULL, NULL, NULL, NULL );
}




//-----------------------------------------------------------------------------
// Name: MsgProc()
// Desc: The window's message handler
//-----------------------------------------------------------------------------
LRESULT WINAPI MsgProc( HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam )
{
    switch( msg )
    {
        case WM_DESTROY:
            Cleanup();
            PostQuitMessage( 0 );
            return 0;
    }

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




//-----------------------------------------------------------------------------
// Name: WinMain()
// Desc: The application's entry point
//-----------------------------------------------------------------------------
INT WINAPI WinMain( HINSTANCE hInst, HINSTANCE, LPSTR, INT )
{
    // Register the window class
    WNDCLASSEX wc = { sizeof(WNDCLASSEX), CS_CLASSDC, MsgProc, 0L, 0L,
                      GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
                      "D3D Tutorial", NULL };
    RegisterClassEx( &wc );

    // Create the application's window
    HWND hWnd = CreateWindow( "D3D Tutorial", "D3D Tutorial 03: Matrices",
                              WS_OVERLAPPEDWINDOW, 100, 100, 640, 480,
                              GetDesktopWindow(), NULL, wc.hInstance, NULL );

    // Initialize Direct3D
    if( SUCCEEDED( InitD3D( hWnd ) ) )
    {
        // Create the vertex buffer
        if( SUCCEEDED( InitVB() ) )
        {
            // 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
                    Render();
            }
        }
    }

    UnregisterClass( "D3D Tutorial", wc.hInstance );
    return 0;
}

文章源地址：http://www.waitingfy.com/?p=216

项目下载： Matrices  （本地下载）

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