opengl - 在窗口调整大小时保持 2D 对象的纵横比

Question

我有一个 Windows (XP) 应用程序需要在窗口中显示一个二维矩形。矩形不得被裁剪(即必须始终完全位于视口(viewport)内)，并且必须在调整大小时保持其纵横比。当前，处理布局的方法会扭曲矩形的纵横比以匹配窗口。我希望矩形缩放到窗口并在窗口中居中(同样，不剪裁)。目前的方法如下。 lWinDist 和 lMaxDepth 是要显示的矩形的宽度和高度(如果重要，以 48 英寸为单位):

void CRoRRecView::RedoLayout( long lWinDist, long lMaxDepth )
{
    CDC* pDC = GetDC() ;

    if ( pDC != NULL )
    {
        m_lWinDist = lWinDist;
        GetClientRect( m_rectClient ) ;
        int nClientWidth = m_rectClient.Width();
        int nClientHeight = m_rectClient.Height();
        glViewport( 0, 0, nClientWidth, nClientHeight );

        glMatrixMode( GL_PROJECTION);
        glLoadIdentity();

        m_fWinXDist = (float) lWinDist ;
        m_fWinYDist = lMaxDepth ;
        m_fAspectRatio = m_fWinXDist / m_fWinYDist;

        glOrtho(0.0, m_fWinXDist, 0.0, m_fWinYDist, -1, 1 ) ;

        glRotatef(180.0, 0,1,0); 
        glTranslatef( (float)(-1 * lWinDist),0,0 ); // Translate across the x axis

        glMatrixMode( GL_MODELVIEW );
        glLoadIdentity();

        ReleaseDC( pDC ) ;
    }
}

Answer 1

试试这个 reshape 函数。它将保持纵横比，调整对象大小，并使视口(viewport)居中。

// initial window screen size
int WIDTH = 400;
int HEIGHT = 300;

// reshape function, call with glutReshapeFunc(reshape) in yout main function
void reshape(int width, int height) {
    const float ar_origin = (float) WIDTH / (float) HEIGHT;
    const float ar_new = (float) width / (float) height;

    float scale_w = (float) width / (float) WIDTH;
    float scale_h = (float) height / (float) HEIGHT;
    if (ar_new > ar_origin) {
        scale_w = scale_h;
    } else {
        scale_h = scale_w;
    }

    float margin_x = (width - WIDTH * scale_w) / 2;
    float margin_y = (height - HEIGHT * scale_h) / 2;

    glViewport(margin_x, margin_y, WIDTH * scale_w, HEIGHT * scale_h);
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glOrtho(0, WIDTH / ar_origin, 0, HEIGHT / ar_origin, 0, 1.0);

    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity() ;
}