OpenGL Study 5

 

 Lesson07

使用三种映射滤镜给立方体添加纹理：线性映射（LINEAR），NEAREST映射，MipMap映射；三者的效果渐增，处理速度递减。

添加通过键盘控制立方体的旋转速度，距离屏幕的距离和映射方法的选择。

在模型中添加光照：环境光（Ambient）和散射光（Diffuse），通过键盘来打开和关闭光照。

创建纹理：

//all setup for OpenGL goes here
bool InitGL(GLvoid)
{
    if(!CreateTextures(_T("Data/CrateSmall.bmp")))
        return false;

    glEnable(GL_TEXTURE_2D);
    //enable smooth shading
    glShadeModel(GL_SMOOTH);
    
    //black background
    glClearColor(0.0f,0.0f,0.0f,0.5f);
    
    //setup the depth buffer
    glClearDepth(1.0f);
    //enable depth testing
    glEnable(GL_DEPTH_TEST);
    //the type of depth test to do
    glDepthFunc(GL_LEQUAL);

    //really nice perspective calculation
    glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);

    //Set up the lighting
    //set the amount of ambient light that light1 will give off
    glLightfv(GL_LIGHT1,GL_AMBIENT,LightAmbient);
    //set the amount of diffues light that light1 will give off
    glLightfv(GL_LIGHT1,GL_DIFFUSE,LightDiffuse);
    //set the position of the light
    glLightfv(GL_LIGHT1,GL_POSITION,LightPosition);
    //Enable the light but it does not start work until GL_LIGHTING is enabled
    glEnable(GL_LIGHT1);

    return true;
}

在创建纹理时，开始使用的图片是256×256大小的，运行时总是在glTexImage2D（）这个函数出出现越界访问错误，分析一下越界信息，发现程序要访问BMP.bmBits[256][256]处的值，这当然越界，可是为什么呢？无奈之下，把图片缩小为128×128的以后，程序就可以正常运行，晕！查看有关glTexImage2D（）的函数，纹理大小都只要no more than 256就可以，为什么，自己的程序就不能使用256的？一直没有搞懂，如果那位高手，知道希望多多指教，谢谢！

加载纹理：

bool CreateTextures(LPTSTR szFileName)                    // Creates Texture From A Bitmap File
{
    HBITMAP hBMP;                                                        // Handle Of The Bitmap
    BITMAP    BMP;                                                        // Bitmap Structure

    glGenTextures(3, &texture[0]);                                            // Create The Texture
    hBMP=(HBITMAP)LoadImage(GetModuleHandle(NULL), szFileName, IMAGE_BITMAP, 0, 0, LR_CREATEDIBSECTION | LR_LOADFROMFILE );

    if (!hBMP)                                                            // Does The Bitmap Exist?
        return false;                                                    // If Not Return False

    GetObject(hBMP, sizeof(BMP), &BMP);                                    // Get The Object
                                                                        // hBMP:        Handle To Graphics Object
                                                                        // sizeof(BMP): Size Of Buffer For Object Information
                                                                        // &BMP:        Buffer For Object Information

    glPixelStorei(GL_UNPACK_ALIGNMENT, 4);                                // Pixel Storage Mode (Word Alignment / 4 Bytes)

    // Typical Texture Generation Using Data From The Bitmap
    //Create Nearest Filtered Texture
    glBindTexture(GL_TEXTURE_2D, texture[0]);                                // Bind To The Texture ID
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);    // Linear Min Filter
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);    // Linear Mag Filter
    glTexImage2D(GL_TEXTURE_2D, 0, 3, BMP.bmWidth, BMP.bmHeight, 0, GL_RGB, GL_UNSIGNED_BYTE, BMP.bmBits);

    //Create Linear Filtered Texture
    glBindTexture(GL_TEXTURE_2D,texture[1]);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexImage2D(GL_TEXTURE_2D,0,3,BMP.bmWidth,BMP.bmHeight,0,GL_RGB,GL_UNSIGNED_BYTE,BMP.bmBits);

    //Create MipMapped Texture
    glBindTexture(GL_TEXTURE_2D,texture[2]);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR_MIPMAP_NEAREST);
    gluBuild2DMipmaps(GL_TEXTURE_2D,3,BMP.bmWidth,BMP.bmHeight,GL_RGB,GL_UNSIGNED_BYTE,BMP.bmBits);


    DeleteObject(hBMP);                                                    // Delete The Object

    return true;                                                        // Loading Was Successful
}

显示立方体：

//here we do all the drawings
bool DrawGLScene(GLvoid)
{
    //clear the screen and the depth buffer
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
    //reset the current modelview matrix
    glLoadIdentity();

    //position and rotate the texture mapped cube
    glTranslatef(0.0f,0.0f,z);
    glRotatef(xrot,1.0f,0.0f,0.0f);
    glRotatef(yrot,0.0f,1.0f,0.0f);

    //bind texture to the cube
    glBindTexture(GL_TEXTURE_2D,texture[filter]);
    glBegin(GL_QUADS);
        // Front Face
        glNormal3f( 0.0f, 0.0f, 1.0f);                    // Normal Pointing Towards Viewer
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Point 1 (Front)
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Point 2 (Front)
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Point 3 (Front)
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Point 4 (Front)
        // Back Face
        glNormal3f( 0.0f, 0.0f,-1.0f);                    // Normal Pointing Away From Viewer
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Point 1 (Back)
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Point 2 (Back)
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Point 3 (Back)
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Point 4 (Back)
        // Top Face
        glNormal3f( 0.0f, 1.0f, 0.0f);                    // Normal Pointing Up
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Point 1 (Top)
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Point 2 (Top)
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Point 3 (Top)
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Point 4 (Top)
        // Bottom Face
        glNormal3f( 0.0f,-1.0f, 0.0f);                    // Normal Pointing Down
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Point 1 (Bottom)
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Point 2 (Bottom)
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Point 3 (Bottom)
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Point 4 (Bottom)
        // Right face
        glNormal3f( 1.0f, 0.0f, 0.0f);                    // Normal Pointing Right
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Point 1 (Right)
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Point 2 (Right)
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Point 3 (Right)
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Point 4 (Right)
        // Left Face
        glNormal3f(-1.0f, 0.0f, 0.0f);                    // Normal Pointing Left
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Point 1 (Left)
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Point 2 (Left)
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Point 3 (Left)
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Point 4 (Left)
    glEnd();

    //increase the rotation angle
    xrot+=xspeed;
    yrot+=yspeed;

    return true;
}

处理键盘响应：

////////////////win32 functions
//the entry point of our windows application
int APIENTRY _tWinMain(HINSTANCE hInstance,
                     HINSTANCE hPrevInstance,
                     LPTSTR    lpCmdLine,
                     int       nCmdShow)
{
    UNREFERENCED_PARAMETER(hPrevInstance);
    UNREFERENCED_PARAMETER(lpCmdLine);

     // TODO: Place code here.
    MSG msg;
    HACCEL hAccelTable;
    bool done=false;
    bool vkF1=false;

    if(!CreateGLWindow(_T("Lesson01"),640,480,16,fullscreen))
    {
        return 0;
    }

    hAccelTable = LoadAccelerators(hInstance, MAKEINTRESOURCE(IDC_LESSON01));
    while(!done)
    {
        if(PeekMessage(&msg,NULL,0,0,PM_REMOVE))
        {
            if(msg.message==WM_QUIT)
            {
                if(vkF1)
                    vkF1=false;
                else
                    done=true;
            }
            else
            {
                TranslateMessage(&msg);
                DispatchMessage(&msg);
            }
        }else
        {
            if(active)
            {
                if(keys[VK_ESCAPE])
                {
                    keys[VK_ESCAPE]=false;
                    done=true;
                }else
                {
                    DrawGLScene();
                    SwapBuffers(hDC);

                    //use lp to avoid when you hold key 'L' that light will change from on to off and off to on all the time during holding
                    if(keys['L']&& !lp)
                    {
                        lp=true;
                        light=!light;
                        if(!light)
                        {
                            glDisable(GL_LIGHTING);
                        }else
                        {
                            glEnable(GL_LIGHTING);
                        }
                    }
                    if(!keys['L'])
                    {
                        lp=false;
                    }

                    //the same reason for fp
                    if(keys['F'] && !fp)
                    {
                        fp=true;
                        filter+=1;
                        if(filter>2)filter=0;
                    }
                    if(!keys['F'])
                    {
                        fp=false;
                    }

                    //if 'Page Up' pressed,move into the screen
                    if(keys[VK_PRIOR])
                    {
                        z-=0.02f;
                    }

                    //if 'Page down' pressed ,move near the user
                    if(keys[VK_NEXT])
                    {
                        z+=0.02f;
                    }

                    //checking the arrow keys
                    if(keys[VK_UP])
                        xspeed-=0.01f;
                    if(keys[VK_DOWN])
                        xspeed+=0.01f;
                    if(keys[VK_RIGHT])
                        yspeed+=0.01f;
                    if(keys[VK_LEFT])
                        yspeed-=0.01f;
                }
            }

            if(keys[VK_F1])
            {
                keys[VK_F1]=false;
                vkF1=true;
                KillGLWindow();
                fullscreen=!fullscreen;
                if(!CreateGLWindow(_T("Textures,Lighting & Keyboard Tutorial"),640,480,16,fullscreen))
                {
                    return 0;
                }
            }
        }
    }

    KillGLWindow();
    return (msg.wParam);
}

 

全部源码：Lesson07.rar