对象在全屏中变得拉伸

Question

我遇到的问题是当我使用全屏时我的对象被拉伸了。我希望它适合全屏坐标，因此它看起来与图像 A 完全相同。我知道 glViewport 确定 OpenGL 绘制到的 window 部分，它可以帮助设置我反对整个window。但是，我没有使用glViewport，而是使用gluOrtho2D。

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图像 A（屏幕尺寸：700、600）

图像 B（全屏尺寸）

gluOrtho2D代码

// this is the initialisation function, called once only
void init() {
    glClearColor(0.0, 0.0, 0.0, 0.0); // set what colour you want the background to be
    glMatrixMode(GL_PROJECTION); // set the matrix mode
    gluOrtho2D(0.0, winWidth, 0.0, winHeight); // set the projection window size in x and y.
}

我原来用的是gluOrtho2D，用来设置二维正交视区

Answer 1

glViewport 定义渲染到的（默认）帧缓冲区区域。

如果你不想渲染到全屏，那么你可以缩小渲染到的区域，glViewport。你可以在边框上放一些黑色条纹。

您的应用程序的宽高比是 winWidth : winHeight

与glutGet分别使用参数GLUT_WINDOW_WIDTHGLUT_WINDOW_HEIGHT可以得到当前window的大小并计算出当前的宽高比：

int currWidth = glutGet( GLUT_WINDOW_WIDTH );
int currHeight = glutGet( GLUT_WINDOW_HEIGHT );

float window_aspcet = (float)currWidth / (float)currHeight;

有了这些信息，视图可以完美地居中于视口：

void display() {

    float app_aspcet = (float)winWidth / (float)winHeight;

    int currWidth = glutGet( GLUT_WINDOW_WIDTH );
    int currHeight = glutGet( GLUT_WINDOW_HEIGHT );

    float window_aspcet = (float)currWidth / (float)currHeight;

    if ( window_aspcet > app_aspcet )
    {
        int width = (int)((float)currWidth * app_aspcet / window_aspcet + 0.5f);
        glViewport((currWidth - width) / 2, 0, width, currHeight);
    }
    else
    {
        int height = (int)((float)currHeight * window_aspcet / app_aspcet + 0.5f);
        glViewport(0, (currHeight - height) / 2, currWidth, height);
    }

    // [...]

}

或者你可以掌握纵横比和正交投影的中心

void display() {

    float app_aspcet = (float)winWidth / (float)winHeight;

    int currWidth = glutGet( GLUT_WINDOW_WIDTH );
    int currHeight = glutGet( GLUT_WINDOW_HEIGHT );

    float window_aspcet = (float)currWidth / (float)currHeight;

    glViewport(0, 0, currWidth, currHeight);

    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    if ( window_aspcet > app_aspcet )
    {
        float delta_width = (float)currWidth * (float)winHeight / (float)currHeight - (float)winWidth;
        gluOrtho2D(-delta_width/2.0f, (float)winWidth + delta_width/2.0f, 0.0, (float)winHeight);    
    }
    else
    {
        float delta_height = (float)currHeight * (float)winWidth / (float)currWidth - (float)winHeight;
        gluOrtho2D(0.0, (float)winWidth, -delta_height/2.0f, (float)winHeight + delta_height/2.0f);
    }

对象在全屏中变得拉伸

Objects become stretched in full screen

c++

opengl

glut