OpenGL Study 4

Lessson06

为立方体贴图，使用纹理

bool LoadGLBitmap(LPTSTR szFileName, GLuint &texid)                    // Creates Texture From A Bitmap File
{
    HBITMAP hBMP;                                                        // Handle Of The Bitmap
    BITMAP    BMP;                                                        // Bitmap Structure

    glGenTextures(1, &texid);                                            // 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
    glBindTexture(GL_TEXTURE_2D, texid);                                // Bind To The Texture ID
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);    // Linear Min Filter
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);    // Linear Mag Filter
    glTexImage2D(GL_TEXTURE_2D, 0, 3, BMP.bmWidth, BMP.bmHeight, 0, GL_BGR_EXT, GL_UNSIGNED_BYTE, BMP.bmBits);

    DeleteObject(hBMP);                                                    // Delete The Object

    return true;                                                        // Loading Was Successful
}


//Resize and initialize the GL window
GLvoid ReSizeGLScene(GLsizei width,GLsizei height)    
{
    //Prevent divide by zero
    if(height==0)        
    {
        height=1;
    }

    //reset the current viewport
    glViewport(0,0,width,height);

    //select the projection matrix
    glMatrixMode(GL_PROJECTION);
    //reset the projection matrix
    glLoadIdentity();

    gluPerspective(45.0,(GLdouble)width/(GLdouble)height,0.1,100.0);

    //select the model view 
    glMatrixMode(GL_MODELVIEW);
    //reset the model view
    glLoadIdentity();
}

//all setup for OpenGL goes here
bool InitGL(GLvoid)
{
    if(!LoadGLBitmap(_T("Data/NeHe.bmp"),texture[0]))
        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);

    return true;
}

//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();
    glTranslatef(0.0f,0.0f,-5.0f);

    glRotatef(xrot,1.0f,0.0f,0.0f);
    glRotatef(yrot,0.0f,1.0f,0.0f);
    glRotatef(zrot,0.0f,0.0f,1.0f);

    glBindTexture(GL_TEXTURE_2D,texture[0]);

    glBegin(GL_QUADS);
        // Front Face
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Bottom Left Of The Texture and Quad
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Bottom Right Of The Texture and Quad
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Top Right Of The Texture and Quad
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Top Left Of The Texture and Quad
        // Back Face
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Bottom Right Of The Texture and Quad
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Top Right Of The Texture and Quad
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Top Left Of The Texture and Quad
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Bottom Left Of The Texture and Quad
        // Top Face
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Top Left Of The Texture and Quad
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Bottom Left Of The Texture and Quad
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Bottom Right Of The Texture and Quad
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Top Right Of The Texture and Quad
        // Bottom Face
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Top Right Of The Texture and Quad
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Top Left Of The Texture and Quad
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Bottom Left Of The Texture and Quad
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Bottom Right Of The Texture and Quad
        // Right face
        glTexCoord2f(1.0f, 0.0f); glVertex3f( 1.0f, -1.0f, -1.0f);    // Bottom Right Of The Texture and Quad
        glTexCoord2f(1.0f, 1.0f); glVertex3f( 1.0f,  1.0f, -1.0f);    // Top Right Of The Texture and Quad
        glTexCoord2f(0.0f, 1.0f); glVertex3f( 1.0f,  1.0f,  1.0f);    // Top Left Of The Texture and Quad
        glTexCoord2f(0.0f, 0.0f); glVertex3f( 1.0f, -1.0f,  1.0f);    // Bottom Left Of The Texture and Quad
        // Left Face
        glTexCoord2f(0.0f, 0.0f); glVertex3f(-1.0f, -1.0f, -1.0f);    // Bottom Left Of The Texture and Quad
        glTexCoord2f(1.0f, 0.0f); glVertex3f(-1.0f, -1.0f,  1.0f);    // Bottom Right Of The Texture and Quad
        glTexCoord2f(1.0f, 1.0f); glVertex3f(-1.0f,  1.0f,  1.0f);    // Top Right Of The Texture and Quad
        glTexCoord2f(0.0f, 1.0f); glVertex3f(-1.0f,  1.0f, -1.0f);    // Top Left Of The Texture and Quad
    glEnd();

    xrot+=0.3f;
    yrot+=0.2f;
    zrot+=0.4f;

    return true;
}

 使用windows中LoadImage()函数读取bmp文件，并且用于纹理的bmp文件的width，height都必须是2的幂，最小64象素，最大256象素

使用纹理时，现要使用glGenTexture()产生纹理名，然后用glBindTexture()将纹理绑定，用glTexImage2D()将读取的bmp数据绑定到纹理，最后使用glTexParameteri（）处理当纹理太大或太小的情况

应用纹理时，先glBindTexture()绑定纹理，对于每个面上的顶点用glTexCoord2f()设定纹理坐标