一些课后思考

1，glTranslatef(-1.5f,0.0f,-6.0f);这里是被观察的物体在移动，还是视点的位置移动呢

我的理解是后者（就好像是照相机在移动位置来捕捉画面那样），默认的物体位置是屏幕中心，向左移动视图并将视图推远以便被观察的物体能进入，试着调整Z坐标的值，可以看到Z越往里面去，物体就越小，越往外面来，物体越大，这和照相机调整焦距类似。

2.使用Flat coloring(单调着色)给几何对象涂上固定的一种颜色。使用Smoothcoloring(平滑着色)将几个顶点的不同颜色混合在一起，创建漂亮的色彩混合。要注意窗口调整大小以及被其他窗口挡住后重新激活时要重新设置Shade Model。

int COpenGLDemoView::DrawGLScene(GLvoid)                                   
{// Here's Where We Do All The Drawing
    glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);    // Clear Screen And Depth Buffer
    glLoadIdentity();                                    // Reset The Current Modelview Matrix
    glTranslatef(-1.5f,0.0f,-6.0f);//物体左移1.5,向内移6,相当于移动镜头一样，让物体进入镜头中
    glBegin(GL_TRIANGLES);                            // 绘制三角形
        glColor3f(1.0f,0.0f,0.0f);
        glVertex3f( 0.0f, 1.0f, 0.0f);                    // 上顶点
        glColor3f(0.0f,1.0f,0.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);                    // 左下
        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);                    // 右下
    glEnd();                                // 三角形绘制结束
     glShadeModel(GL_FLAT);    
glTranslatef(3.0f,0.0f,0.0f);
glBegin(GL_QUADS);                            //  绘制正方形
        glColor3f(1.0f,0.0f,0.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f);                    // 左上

        glColor3f(1.0,1.0f,1.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);                    // 右下

        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);                    // 左下

        glColor3f(0.0f,1.0f,0.0f);
        glVertex3f( 1.0f, 1.0f, 0.0f);                    // 右上    
    glEnd();                                // 正方形绘制结束
    glFlush();
    return TRUE;                                        // Everything Went OK
}

void COpenGLDemoView::OnActivateView(BOOL bActivate, CView* pActivateView, CView* pDeactiveView) 
{
    // TODO: Add your specialized code here and/or call the base class
    InitGL();//激活窗口时强制要求还原openGL状态
    
    CView::OnActivateView(bActivate, pActivateView, pDeactiveView);
}


void COpenGLDemoView::OnSize(UINT nType, int cx, int cy) 
{
    CView::OnSize(nType, cx, cy);
    
    // TODO: Add your message handler code here
    GLsizei width,height;
    width = cx;
    height = cy;
    if (height==0)                                        // Prevent A Divide By Zero By
    {
        height=1;                                        // Making Height Equal One
    }

    glShadeModel(GL_SMOOTH);
    glViewport(0,0,width,height);                        // Reset The Current Viewport

    glMatrixMode(GL_PROJECTION);                        // Select The Projection Matrix
    glLoadIdentity();                                    // Reset The Projection Matrix
    // Calculate The Aspect Ratio Of The Window
    gluPerspective(45.0f,(GLfloat)width/(GLfloat)height,0.1f,100.0f);//透视投影
    glMatrixMode(GL_MODELVIEW);                            // Select The Modelview Matrix
    glLoadIdentity();                                    // Reset The Modelview Matrix
}


BOOL COpenGLDemoView::InitGL(GLvoid)                                        // All Setup For OpenGL Goes Here
{
    glShadeModel(GL_SMOOTH);                            // Enable Smooth Shading
       glClearColor(0.0,0.0,0.0,0.0);// 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
    return TRUE;                                        // Initialization Went OK
}

3，如果是下面这样设置颜色，则请问正方形的颜色会是怎么样的呢？

glShadeModel(GL_FLAT);    
glTranslatef(3.0f,0.0f,0.0f);
glBegin(GL_QUADS);                            //  绘制正方形
        glColor3f(1.0f,0.0f,0.0f);
        glVertex3f(-1.0f, 1.0f, 0.0f);                    // 左上

        glColor3f(1.0,1.0f,1.0f);
        glVertex3f(-1.0f,-1.0f, 0.0f);                    // 右下

        glColor3f(0.0f,0.0f,1.0f);
        glVertex3f( 1.0f,-1.0f, 0.0f);                    // 左下

        glColor3f(0.0f,1.0f,0.0f);
        glVertex3f( 1.0f, 1.0f, 0.0f);                    // 右上    
    glEnd();                                // 正方形绘制结束

    呵呵，答案是：颜色会是绿色的，也就是说是以最后那个顶点的颜色为标准的，这是因为Flat coloring(单调着色)是会给四边形涂上固定的一种颜色，而最后一个顶点的颜色设置后，就覆盖了前面的颜色设置。