موضوع: دايركت اكس 8

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  1. #1

    Smile دايركت اكس 8

    IntroductionIn our last tutorial we drew a 2D triangle. That was good, but this time we are going to create our very first 3D object... a cube. And to show that it really is 3D, we are going to rotate it about the x, y and z axis. Remember that all 3D objects are made up from polygons, normally triangles. So for our cube, we will use 12 triangles (2 for each face). You can download the full source code and tutorial text by clicking the "Download Source" and "Download Tutorial" links above.3D World SpaceIn the last tutorial we saw how the Left-Handed 3D Coordinate System worked. This is the coordinate system that we will use from now on. We will specify in our code (below) that the y axis points up.

    What is the difference between left and right-handed coordinate systems? In left-handed coordinates, the positive z axis points away from you. In right-handed coordinates, the positive z axis points towards you. In both cases the positive y axis points up and the positive x axis points to the right. You can remember this by holding up your left hand so that the palm is facing up (y axis) and your fingers point to the right (x axis). Your thumb represents the positive z axis (points away). If you did the same with your right hand, your thumb would point towards you, hence left and right-handed coordinate systems. We will always use the left-handed system, this is what DirectX uses. Backface CullingWhat is Backface Culling? Backface Culling is a pretty simple concept. Basically, it is a process where all of the polygons that are "facing" away from the user are not rendered. For example, I have created a square with one side red and the other blue. Let's say that I defined the polygons so that the red side was "facing" the user and then started rotating the square. With Backface Culling enabled, the user would only see the red face and would never see the blue face. Why is this useful? Well, if we are creating a closed 3D object (like a cube), we do not need to render the inside faces because they are never seen anyway. This makes the rendering of a cube more efficient.

    How do I specify which face is "facing" the user and which face to cull (not render)? It's all in the order that you specify your vertices. Below are two diagrams showing the order in which to define a "Clockwise" polygon. If you created a polygon in this way, the polygon would be rendered as shown, but if you were to flip the polygon (rotate), it would not be rendered. You can define which faces are culled, clockwise or anti-clockwise. By default, DirectX will cull anti-clockwise polygons. Fig 3.1Fig 3.2How to make a cubeBelow are two diagrams showing how our cube is going to be made up. Here we have used three triangle strips, one for the top of the cube, one for the sides and one for the bottom. The diagram below shows the vertices and polygons for each triangle strip (Fig 3.3). The vertices are numbered from 0 to 17, this is the order that we must specify our vertices in the vertex buffer. Under that is a diagram that shows our cube (Fig 3.4). Notice where each of the vertices are in relation to each other. Also, look at how the vertices are always in a clockwise direction (except the bottom). This is because we have enabled Backface Culling (see above). Fig 3.3Fig 3.4MatricesWhat is a Matrix? Matrices are a pretty advanced mathematics topic, so I will only give you a brief summary. A matrix can be thought of as a grid of numbers that can be applied to the coordinates of a vertex to change their values. You can use matrices in DirectX to translate, rotate and scale objects (vertices). In DirectX, a matrix is a 4x4 grid of numbers. There are three types of matrix: World, View and Projection.

    World Matrix
    You can use the world matrix to rotate, scale and translate objects in 3D space (World Space) by modifying their vertices. All of these transformations will be performed about the origin (0, 0, 0). You can combine transformations by multiplying them together, but be aware that it is important which order you perform the multiplication. Matrix1 x Matrix2 is not the same as Matrix2 x Matrix1. When you perform a world matrix transformation, all subsequent vertices will be transformed by this matrix. To rotate two objects, one about the x axis and one about the y axis, you must perform the x axis transformation first, then render object 1. Next, perform the y axis transformation, then render object 2.

    View Matrix
    The view matrix is the camera (or eye). The camera has a position in world space and also has a "look at" position. For example, you can place the camera above an object (camera position) and point it at the centre of the object (look at position). You can also specify which way is up, in our example below we will specify that the positive y axis is up.

    Projection Matrix
    The projection matrix can be thought of as the camera lens. It specifies the field of view angle, aspect ratio and near/far clipping planes. For the time being at least, we will keep these settings the same throughout our examples. Here is the code for this tutorial. It's just the same as the code from the last tutorial, except for a few modifications:#include <d3dx8.h>

    LPDIRECT3D8 g_pD3D = NULL;
    LPDIRECT3DVERTEXBUFFER8 g_pVertexBuffer = NULL; // Buffer to hold vertices

    FLOAT x, y, z;
    DWORD colour;


    #define SafeRelease(pObject) if(pObject != NULL) {pObject->Release(); pObject=NULL;}

    HRESULT InitialiseD3D(HWND hWnd)
    //First of all, create the main D3D object. If it is created successfully we
    //should get a pointer to an IDirect3D8 interface.
    g_pD3D = Direct3DCreate8(D3D_SDK_VERSION);
    if(g_pD3D == NULL)
    return E_FAIL;

    //Get the current display mode
    if(FAILED(g_pD3D->GetAdapterDisplayMode(D3DADAPTER_DEFAULT, &d3ddm)))
    return E_FAIL;

    //Create a structure to hold the settings for our device
    ZeroMemory(&d3dpp, sizeof(d3dpp));

    //Fill the structure.
    //We want our program to be windowed, and set the back buffer to a format
    //that matches our current display mode
    d3dpp.Windowed = TRUE;
    d3dpp.SwapEffect = D3DSWAPEFFECT_COPY_VSYNC;
    d3dpp.BackBufferFormat = d3ddm.Format;

    //Create a Direct3D device.
    return E_FAIL;

    //Turn on back face culling. This is becuase we want to hide the back of our polygons
    g_pD3DDevice->SetRenderState(D3DRS_CULLMODE, D3DCULL_CCW);

    //Turn off lighting becuase we are specifying that our vertices have colour
    g_pD3DDevice->SetRenderState(D3DRS_LIGHTING, FALSE);

    return S_OK;

    HRESULT InitialiseVertexBuffer()
    VOID* pVertices;

    //Store each point of the cube together with it's colour
    //Make sure that the points of a polygon are specified in a clockwise direction,
    //this is because anti-clockwise faces will be culled
    //We will use a three triangle strips to render these polygons (Top, Sides, Bottom).
    CUSTOMVERTEX cvVertices[] =
    //Top Face
    {-5.0f, 5.0f, -5.0f, D3DCOLOR_XRGB(0, 0, 255),}, //Vertex 0 - Blue
    {-5.0f, 5.0f, 5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 1 - Red
    {5.0f, 5.0f, -5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 2 - Red
    {5.0f, 5.0f, 5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 3 - Green

    //Face 1
    {-5.0f, -5.0f, -5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 4 - Red
    {-5.0f, 5.0f, -5.0f, D3DCOLOR_XRGB(0, 0, 255),}, //Vertex 5 - Blue
    {5.0f, -5.0f, -5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 6 - Green
    {5.0f, 5.0f, -5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 7 - Red

    //Face 2
    {5.0f, -5.0f, 5.0f, D3DCOLOR_XRGB(0, 0, 255),}, //Vertex 8 - Blue
    {5.0f, 5.0f, 5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 9 - Green

    //Face 3
    {-5.0f, -5.0f, 5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 10 - Green
    {-5.0f, 5.0f, 5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 11 - Red

    //Face 4
    {-5.0f, -5.0f, -5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 12 - Red
    {-5.0f, 5.0f, -5.0f, D3DCOLOR_XRGB(0, 0, 255),}, //Vertex 13 - Blue

    //Bottom Face
    {5.0f, -5.0f, -5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 14 - Green
    {5.0f, -5.0f, 5.0f, D3DCOLOR_XRGB(0, 0, 255),}, //Vertex 15 - Blue
    {-5.0f, -5.0f, -5.0f, D3DCOLOR_XRGB(255, 0, 0),}, //Vertex 16 - Red
    {-5.0f, -5.0f, 5.0f, D3DCOLOR_XRGB(0, 255, 0),}, //Vertex 17 - Green

    //Create the vertex buffer from our device.
    if(FAILED(g_pD3DDevice->CreateVertexBuffer(18 * sizeof(CUSTOMVERTEX),
    D3DPOOL_DEFAULT, &g_pVertexBuffer)))
    return E_FAIL;

    //Get a pointer to the vertex buffer vertices and lock the vertex buffer
    if(FAILED(g_pVertexBuffer->Lock(0, sizeof(cvVertices), (BYTE**)&pVertices, 0)))
    return E_FAIL;

    //Copy our stored vertices values into the vertex buffer
    memcpy(pVertices, cvVertices, sizeof(cvVertices));

    //Unlock the vertex buffer

    return S_OK;

    void SetupRotation()
    //Here we will rotate our world around the x, y and z axis.
    D3DXMATRIX matWorld, matWorldX, matWorldY, matWorldZ;

    //Create the transformation matrices
    D3DXMatrixRotationX(&matWorldX, timeGetTime()/400.0f);
    D3DXMatrixRotationY(&matWorldY, timeGetTime()/400.0f);
    D3DXMatrixRotationZ(&matWorldZ, timeGetTime()/400.0f);

    //Combine the transformations by multiplying them together
    D3DXMatrixMultiply(&matWorld, &matWorldX, &matWorldY);
    D3DXMatrixMultiply(&matWorld, &matWorld, &matWorldZ);

    //Apply the tansformation
    g_pD3DDevice->SetTransform(D3DTS_WORLD, &matWorld);

    void SetupCamera()
    //Here we will setup the camera.
    //The camera has three settings: "Camera Position", "Look at Position" and "Up Direction"
    //We have set the following:
    //Camera Position: (0, 0, -30)
    //Look at Position: (0, 0, 0)
    //Up direction: Y-Axis.
    D3DXMATRIX matView;
    D3DXMatrixLookAtLH(&matView, &D3DXVECTOR3(0.0f, 0.0f,-30.0f), //Camera Position
    &D3DXVECTOR3(0.0f, 0.0f, 0.0f), //Look At Position
    &D3DXVECTOR3(0.0f, 1.0f, 0.0f)); //Up Direction
    g_pD3DDevice->SetTransform(D3DTS_VIEW, &matView);

    void SetupPerspective()
    //Here we specify the field of view, aspect ration and near and far clipping planes.
    D3DXMATRIX matProj;
    D3DXMatrixPerspectiveFovLH(&matProj, D3DX_PI/4, 1.0f, 1.0f, 500.0f);
    g_pD3DDevice->SetTransform(D3DTS_PROJECTION, &matProj);

    void Render()
    if(g_pD3DDevice == NULL)

    //Clear the backbuffer to black
    g_pD3DDevice->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_XRGB(0, 0, 0), 1.0f, 0);

    //Begin the scene

    //Setup the rotation, camera, and perspective matrices

    //Rendering our objects
    g_pD3DDevice->SetStreamSource(0, g_pVertexBuffer, sizeof(CUSTOMVERTEX));
    g_pD3DDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP, 0, 2); //Top
    g_pD3DDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP, 4, 8); //Sides
    g_pD3DDevice->DrawPrimitive(D3DPT_TRIANGLESTRIP, 14, 2); //Bottom

    //End the scene

    //Filp the back and front buffers so that whatever has been rendered on the back buffer
    //will now be visible on screen (front buffer).
    g_pD3DDevice->Present(NULL, NULL, NULL, NULL);

    void CleanUp()

    void GameLoop()
    //Enter the game loop
    MSG msg;
    BOOL fMessage;

    PeekMessage(&msg, NULL, 0U, 0U, PM_NOREMOVE);

    while(msg.message != WM_QUIT)
    fMessage = PeekMessage(&msg, NULL, 0U, 0U, PM_REMOVE);

    //Process message
    //No message to process, so render the current scene


    //The windows message handler
    LRESULT WINAPI WinProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
    case WM_DESTROY:
    return 0;
    case WM_KEYUP:
    switch (wParam)
    case VK_ESCAPE:
    //User has pressed the escape key, so quit
    return 0;


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

    //Application entry point
    //Register the window class
    WNDCLASSEX wc = {sizeof(WNDCLASSEX), CS_CLASSDC, WinProc, 0L, 0L,
    GetModuleHandle(NULL), NULL, NULL, NULL, NULL,
    "DX Project 3", NULL};

    //Create the application's window
    HWND hWnd = CreateWindow("DX Project 3", "www.andypike.com: Tutorial 3",
    WS_OVERLAPPEDWINDOW, 50, 50, 500, 500,
    GetDesktopWindow(), NULL, wc.hInstance, NULL);

    //Initialize Direct3D
    //Show our window
    ShowWindow(hWnd, SW_SHOWDEFAULT);

    //Initialize Vertex Buffer
    //Start game running: Enter the game loop


    UnregisterClass("DX Project 3", wc.hInstance);

    return 0;

    You should finish up with a window with a black background and a multi-coloured cube in the middle rotating (shown below).

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