c++ - 无法在窗口中正确 reshape 多边形

Question

我正在尝试开发一个程序，每次在窗口上执行点击时，一个随机大小的圆圈会出现在以点击发生的位置为中心的窗口上。 之后，我需要使用 glOrtho() 或 gluOrtho2D() 以便以这样的方式设置查看体积:当调整窗口大小时，圆圈不会改变它们的大小或在屏幕上变形。

我尝试用不同的方式编写 reshape 函数，但我无法得到正确的结果。

int winWidth = 800;             
int winHeight = 600; 

int main( int argc, char** argv )
{
    glutInit( &argc, argv );
    glutInitDisplayMode( GLUT_RGB | GLUT_SINGLE );  
    glutInitWindowSize( winWidth, winHeight );
    glutCreateWindow( "main" );

    MyInit();

    glutDisplayFunc( MyDisplay );
    glutReshapeFunc( MyReshape );
    glutMouseFunc( MyMouse );

    glutMainLoop();
    return 0;
}

void MyReshape( int w, int h )
{
    winWidth = w;
    winHeight = h;

    glViewport( 0, 0, w, h );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    if (w <= h)
        glOrtho(-2.0, 2.0, -2.0 * (GLfloat) h / (GLfloat) w,
            2.0 * (GLfloat) h / (GLfloat) w, -20.0, 20.0);
    else
        glOrtho(-2.0 * (GLfloat) w / (GLfloat) h,
            2.0 * (GLfloat) w / (GLfloat) h, -2.0, 2.0, -20.0, 20.0);

    glMatrixMode( GL_MODELVIEW );

}

void MyMouse( int btn, int state, int x, int y )
{
    if ( btn == GLUT_LEFT_BUTTON && state == GLUT_DOWN )
    {
        disc[numDiscs].pos[0] = x;
        disc[numDiscs].pos[1] = y;
        disc[numDiscs].speed[0] = ((rand() % 2) * 2 - 1) * (MIN_X_SPEED + rand() / (RAND_MAX / (MAX_X_SPEED - MIN_X_SPEED)));
        disc[numDiscs].speed[1] = ((rand() % 2) * 2 - 1) * (MIN_Y_SPEED + rand() / (RAND_MAX / (MAX_Y_SPEED - MIN_Y_SPEED)));
        disc[numDiscs].radius = (MIN_RADIUS + rand() / (RAND_MAX / (MAX_RADIUS - MIN_RADIUS)))/10;
        disc[numDiscs].color[0] = (char)rand() % 256;
        disc[numDiscs].color[1] = (char)rand() % 256;
        disc[numDiscs].color[2] = (char)rand() % 256;

        numDiscs++;
        glutPostRedisplay();
    }
}

void MyDisplay( void )
{
    glClear( GL_COLOR_BUFFER_BIT );
    glPolygonMode( GL_FRONT_AND_BACK, GL_FILL );

    for ( int i = 0; i < numDiscs; i++ ) DrawDisc( &disc[i] );

    glFlush();  
}

void MyInit( void )
{
    glClearColor( 0.0, 0.0, 0.0, 1.0 ); 
    glShadeModel( GL_FLAT );
}

Answer 1

[...] in such a way that when the window is resized, the circles do not change their sizes or get distorted [...]

如果圆应该以像素为单位保持大小，那么您必须定义一个正交投影，它基于窗口的当前大小与窗口初始大小的关系。
由于窗口的大小是 (800, 600)，因此您必须根据窗口的高度分别将投影缩放 w/600.0 h/600.0，因为高度小于宽度，并且 aspect 应用于较长的边:

void MyReshape( int w, int h )
{
    winWidth = w;
    winHeight = h;

    glViewport( 0, 0, w, h );

    glMatrixMode( GL_PROJECTION );
    glLoadIdentity();
    if (w <= h)
    {
        GLdouble  aspect = (GLdouble)h / w;
        GLdouble  scale  = w / 600.0;

        scale *= 2.0;
        project = glm::ortho(-scale, scale, -scale * aspect, scale * aspect, -20.0, 20.0);
    }
    else
    {
        GLdouble  aspect = (GLdouble)w / h;
        GLdouble  scale  = h / 600.0;

        scale *= 2.0;
        project = glm::ortho(-scale * aspect, scale * aspect, -scale, scale, -20.0, 20.0);
    }
    glMatrixMode( GL_MODELVIEW );
}