飘动的风景画（NEHE经典教程MFC下的实现：LESSON11)

不再多说，首先按《基于MFC的OpenGL编程》Part 2 Setting up OpenGL on Windows中的介绍，把所有该做的东西都先做好。

1.增加变量

float points[45][45][3]; // The Array For The Points On The Grid Of Our "Wave"
int wiggle_count;        // Counter Used To Control How Fast Flag Waves

    GLfloat    xrot;                // X Rotation ( NEW )
    GLfloat    yrot;                // Y Rotation ( NEW )
    GLfloat    zrot;                // Z Rotation ( NEW )
    GLfloat hold;                // Temporarily Holds A Floating Point Value

    GLuint    texture[1];            // Storage For One Texture ( NEW )

 本例虽然只有一幅图片来作为纹理，但是为了让他看起来能动。不是把它整个的贴在一个矩形里面，而是放到44X44个矩阵里面，所以设置了points这个数组来存储各个顶点的x,y,z值。其它的变量就不解释了。

2.这是用来读入BMP图像的函数，关键代码其实就auxDIBImageLoad(Filename)，其它的都是用来防止出错的，程序的健壮性相当的好啊。

AUX_RGBImageRec* CdemoView::LoadBMP(char* Filename)
{
    FILE *File=NULL;                                    // File Handle

    if (!Filename)                                        // Make Sure A Filename Was Given
    {
        return NULL;                                    // If Not Return NULL
    }

    File=fopen(Filename,"r");                            // Check To See If The File Exists

    if (File)                                            // Does The File Exist?
    {
        fclose(File);                                    // Close The Handle
return auxDIBImageLoad(Filename);                // Load The Bitmap And Return A Pointer
    }

    return NULL;                                        // If Load Failed Return NULL

}

3.载入纹理：GenT -> BindT ->TImg -> TParameter。这个过程如果熟悉的话，是个很简单的过程，主要参数的意义需要理清楚。NEHE的程序总是很完美，该释放的变量和空间绝不保留。

int CdemoView::LoadGLTextures(void)
{
    int Status=FALSE;                                    // Status Indicator

    AUX_RGBImageRec *TextureImage[1];                    // Create Storage Space For The Texture

    memset(TextureImage,0,sizeof(void*)*1);               // Set The Pointer To NULL

    // Load The Bitmap, Check For Errors, If Bitmap's Not Found Quit
if (TextureImage[0]=LoadBMP("Data/Tim.bmp"))
    {
        Status=TRUE;                                    // Set The Status To TRUE

        glGenTextures(1, &texture[0]);                    // Create The Texture

        // Typical Texture Generation Using Data From The Bitmap
        glBindTexture(GL_TEXTURE_2D, texture[0]);
        glTexImage2D(GL_TEXTURE_2D, 0, 3, TextureImage[0]->sizeX,

　　　　　　 TextureImage[0]->sizeY, 0, GL_RGB, GL_UNSIGNED_BYTE, TextureImage[0]->data);
        glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MIN_FILTER,GL_LINEAR);
        glTexParameteri(GL_TEXTURE_2D,GL_TEXTURE_MAG_FILTER,GL_LINEAR);
    }

    if (TextureImage[0])                                    // If Texture Exists
    {
        if (TextureImage[0]->data)                            // If Texture Image Exists
        {
            free(TextureImage[0]->data);                    // Free The Texture Image Memory
        }

        free(TextureImage[0]);                                // Free The Image Structure
    }

    return Status;                                        // Return The Status

}

4.InitializeOpenGL函数需要做一些改动，我把整个函数都贴上来了。主要就是加了对二维纹理映射和数组（即各个矩形顶点）的初始化。

BOOL CdemoView::InitializeOpenGL(void)
{
    //Get a DC for the Client Area
    m_pDC =new CClientDC(this);
    //Failure to Get DC
if(m_pDC == NULL)
    {
        MessageBox("Error Obtaining DC");
        return FALSE;
    }
    //Failure to set the pixel format
if(!SetupPixelFormat())
    {
        return FALSE;
    }
    //Create Rendering Context
    m_hRC = ::wglCreateContext (m_pDC->GetSafeHdc ());
    //Failure to Create Rendering Context
if(m_hRC ==0)
    {
        MessageBox("Error Creating RC");
        return FALSE;
    }
    //Make the RC Current
if(::wglMakeCurrent (m_pDC->GetSafeHdc (), m_hRC)==FALSE)
    {
        MessageBox("Error making RC Current");
        return FALSE;
    }

        if (!LoadGLTextures())                                // Jump To Texture Loading Routine ( NEW )
    {
        return FALSE;                                    // If Texture Didn't Load Return FALSE
    }

    glEnable(GL_TEXTURE_2D);                            // Enable Texture Mapping ( NEW )
    glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
    glClearColor(0.0f, 0.0f, 0.0f, 0.5f);                // Black Background
    glClearDepth(1.0f);                                    // Depth Buffer Setup
    glEnable(GL_DEPTH_TEST);                            // Enables Depth Testing
    glDepthFunc(GL_LEQUAL);                                // The Type Of Depth Testing To Do
    glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_NICEST);    // Really Nice Perspective Calculations
    glPolygonMode( GL_BACK, GL_FILL );                    // Back Face Is Solid
    glPolygonMode( GL_FRONT, GL_LINE );                    // Front Face Is Made Of Lines

    for(int x=0; x<45; x++)
    {
        for(int y=0; y<45; y++)
        {
            points[x][y][0]=float((x/5.0f)-4.5f);
            points[x][y][1]=float((y/5.0f)-4.5f);
            points[x][y][2]=float(sin((((x/5.0f)*40.0f)/360.0f)*3.141592654*2.0f));
        }
    }

    return TRUE;
}

5.渲染函数了,RenderScene，这个程序的精华也就在这里了。

void CdemoView::RenderScene(void)
{
    int x, y;
    float float_x, float_y, float_xb, float_yb;

    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);    // Clear The Screen And The Depth Buffer
    glLoadIdentity();                                    // Reset The View

    glTranslatef(0.0f,0.0f,-12.0f);

分别以x,y,z轴为中心就行旋转，这样图像作为一个整体会有动态的效果。

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

下面这段要仔细看看，如何把纹理贴到这个44X44的网格上面去。

    glBindTexture(GL_TEXTURE_2D, texture[0]);

    glBegin(GL_QUADS);
    for( x =0; x <44; x++ )
    {
        for( y =0; y <44; y++ )
        {
            float_x =float(x)/44.0f;
            float_y =float(y)/44.0f;
            float_xb =float(x+1)/44.0f;
            float_yb =float(y+1)/44.0f;

            glTexCoord2f( float_x, float_y);
            glVertex3f( points[x][y][0], points[x][y][1], points[x][y][2] );

            glTexCoord2f( float_x, float_yb );
            glVertex3f( points[x][y+1][0], points[x][y+1][1], points[x][y+1][2] );

            glTexCoord2f( float_xb, float_yb );
            glVertex3f( points[x+1][y+1][0], points[x+1][y+1][1], points[x+1][y+1][2] );

            glTexCoord2f( float_xb, float_y );
            glVertex3f( points[x+1][y][0], points[x+1][y][1], points[x+1][y][2] );
        }
    }
    glEnd();

撇开图像整体沿x,y,z轴的旋转，飘动的效果是由下面的代码完成的。

if( wiggle_count ==2 )
    {
        for( y =0; y <45; y++ )
        {
            hold=points[0][y][2];
            for( x =0; x <44; x++)
            {
                points[x][y][2] = points[x+1][y][2];
            }
            points[44][y][2]=hold;
        }
        wiggle_count =0;
    }

}

6.记得在ONCREATE函数下面加上SetTimer这个函数。

void CdemoView::OnTimer(UINT_PTR nIDEvent)
{
    // TODO: Add your message handler code here and/or call default
    wiggle_count++;

    xrot+=0.3f;
    yrot+=0.2f;
    zrot+=0.4f;
    InvalidateRect(NULL,FALSE);
    CView::OnTimer(nIDEvent);
}

7.好了，运行程序。效果如下：

 纹理贴在正面，背面是由线组成的，所以能看到正面的内容。