Question

我正在尝试学习|| Qt中的代码openGL。我做了一个显示两个数字的应用程序。一个是三角形“A”，另一个三角形“B”与“A”相同，只是它围绕z轴旋转了-90度（z轴垂直于计算机屏幕）。现在，问题是轮换使维度发生变化。我发布了下面的“main.cpp”，

#include <QApplication>
#include <QHBoxLayout>
#include <QMessageBox>
#include <QtOpenGL/QGLWidget>
#include <QWidget>

class MyOpenGL:public QGLWidget
{
public:
    MyOpenGL(QWidget * parent);
    ~MyOpenGL();
    void initializeGL();
    void resizeGL(int w, int h);
    void paintGL();
};

MyOpenGL::MyOpenGL(QWidget *parent):QGLWidget(QGLFormat(QGL::SampleBuffers),parent)
{
    setAutoFillBackground(false);
}

MyOpenGL::~MyOpenGL()
{

}

void MyOpenGL::initializeGL()
{
    glShadeModel(GL_SMOOTH);
    glClearColor(0.0f,0.0f,0.0f,0.0f);
    glClearDepth(1.0f);
    glEnable(GL_DEPTH_TEST);
    glDepthFunc(GL_LEQUAL);
    glHint(GL_PERSPECTIVE_CORRECTION_HINT,GL_NICEST);
}

void MyOpenGL::resizeGL(int w, int h)
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    gluPerspective(45.0f,width()/height(),10.0f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
}

void MyOpenGL::paintGL()
{
    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    //glTranslatef(0.0,0.0,-10.0);

    glBegin(GL_TRIANGLES);
    glColor3f(1.0f,0.0f,0.0f);
    glVertex3f(-1.0f,0.0f,-10.0f);
    glColor3f(0.0f,1.0f,0.0f);
    glVertex3f(1.0f,0.0f,-10.0f);
    glColor3f(0.0f,0.0f,1.0f);
    glVertex3f(0.0f,4.0f,-10.0f);
    glEnd();

    glRotatef(90.0,0.0f,0.0f,-1.0f);

    glBegin(GL_TRIANGLES);
    glColor3f(1.0f,0.0f,0.0f);
    glVertex3f(-1.0f,0.0f,-10.0f);
    glColor3f(0.0f,1.0f,0.0f);
    glVertex3f(1.0f,0.0f,-10.0f);
    glColor3f(0.0f,0.0f,1.0f);
    glVertex3f(0.0f,4.0f,-10.0f);
    glEnd();

    glLoadIdentity();
}

int main(int argc,char * argv[])
{
    QApplication app(argc,argv);

    MyOpenGL * f = new MyOpenGL(NULL);
    f->show();

    return app.exec();
}

这是专业档案

SOURCES += \
    main.cpp

QT += opengl

这是应用程序的屏幕截图

enter image description here

据我所知，轮换不会对尺寸做任何改变。但这里的维度正在发生变化。如果有人在这个问题上表示怀疑，我将非常感谢他/她。

Answer 1

我不能确定发生了什么，但我确实看到可能存在一些问题。

gluPerspective(45.0f,width()/height(),10.0f,100.0f);

如果width和height都返回整数（他们可能会这样做），那么将一个除以另一个将导致整数。这不会给你一个适当的宽高比。将其中一个投射到浮子上以获得真实的纵横比。

接下来，尝试将glLoadIdentity（）调用放在paintGL函数的顶部。

Answer 2

如果您需要2D渲染，请使用gluOrtho2D而不是gluPerspective（3D渲染）。

实际上，这不是问题，这只是将3D物体正常投影到2D平面上。

Answer 3

您需要设置视图：

void MyOpenGL::resizeGL(int w, int h)
{
    glMatrixMode(GL_PROJECTION);
    glLoadIdentity();
    glViewport(0,0,w,h);
    gluPerspective(45.0f,(double)w/(double)h,10.0f,100.0f);
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();
    updateGL();
}

此外，渲染图像时无需重置投影矩阵：

void MyOpenGL::paintGL()
{
    glMatrixMode(GL_MODELVIEW);
    glLoadIdentity();


    glClear(GL_COLOR_BUFFER_BIT|GL_DEPTH_BUFFER_BIT);

    //glTranslatef(0.0,0.0,-10.0);

    glBegin(GL_TRIANGLES);
    glColor3f(1.0f,0.0f,0.0f);
    glVertex3f(-1.0f,0.0f,-10.0f);
    glColor3f(0.0f,1.0f,0.0f);
    glVertex3f(1.0f,0.0f,-10.0f);
    glColor3f(0.0f,0.0f,1.0f);
    glVertex3f(0.0f,4.0f,-10.0f);
    glEnd();

    glRotatef(90.0,0.0f,0.0f,-1.0f);

    glBegin(GL_TRIANGLES);
    glColor3f(1.0f,0.0f,0.0f);
    glVertex3f(-1.0f,0.0f,-10.0f);
    glColor3f(0.0f,1.0f,0.0f);
    glVertex3f(1.0f,0.0f,-10.0f);
    glColor3f(0.0f,0.0f,1.0f);
    glVertex3f(0.0f,4.0f,-10.0f);
    glEnd();
}

但有人说，尝试使用glOrtho而不是gluPerspective

Answer 4

要进行旋转，您必须先将事物带到原点，然后旋转，然后将其放到所需的位置。

OpenGL - 旋转问题 - Qt

4 个答案: