OpenGL 获取当前屏幕坐标的三维坐标（gluUnProject使用例子 Qt）

之前使用VS+glut实现了gluUnProject使用例子，用于渲染管道的逆过程，将屏幕坐标转换为opengl三维坐标，本文将尝试使用QT来实现。

代码如下：

main.cpp

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#include "GLWidget.h"
#include <QApplication>

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

GLWidget glw;
    glw.resize();
    glw.setWindowTitle("gluUnProject Demo");
    glw.show();

return a.exec();
}

GLWidget.h

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#ifndef GLWIDGET_H
#define GLWIDGET_H

#include <QGLWidget>

class GLWidget : public QGLWidget
{
Q_OBJECT

public:
GLWidget(QWidget *parent = );
~GLWidget();

protected:
    virtual void initializeGL();
    virtual void resizeGL(int w, int h);
    virtual void paintGL();

virtual void mousePressEvent(QMouseEvent *event);

private:
    void draw();
    void DrawFloor();
    void DrawAxis();

GLdouble   objx;
    GLdouble   objy;
    GLdouble   objz;
};

#endif // GLWIDGET_H

GLWidget.cpp

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#include "GLWidget.h"
#include <QMouseEvent>
#include <GL/glu.h>
#include <QDebug>

;

GLWidget::GLWidget(QWidget *parent)
    : QGLWidget(parent)
{
    objx = ;
    objy = ;
    objz = ;
}

GLWidget::~GLWidget()
{

}

void GLWidget::initializeGL()
{
glClearColor();

glClearDepth();
glEnable(GL_DEPTH_TEST);
glDepthFunc(GL_LEQUAL);
}

void GLWidget::resizeGL(int w, int h)
{
    ];
    glViewport( , w, h );
    glGetIntegerv( GL_VIEWPORT, viewport );
    glMatrixMode( GL_PROJECTION );
    glLoadIdentity( );
    gluPerspective(  );
    ];
    glGetDoublev( GL_PROJECTION_MATRIX, projection );
    glMatrixMode( GL_MODELVIEW );
    glLoadIdentity( );
    gluLookAt(  );
}

void GLWidget::paintGL()
{

glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT );

//The big gray floor like polygon
    glBegin( GL_POLYGON );
    glColor3f(  );
    glVertex3f( -  );
    glVertex3f( -  );
    glVertex3f(  );
    glVertex3f(  );
    glEnd( );
    //DrawFloor();
    DrawAxis();

//The red cube to be drawn at clicked position
    glPushMatrix( );
    glTranslatef(objx, objy, objz );
    draw();
    ];
    glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
    glPopMatrix( );
}

void GLWidget::mousePressEvent(QMouseEvent *event)
{
    updateGL();
    ];
    ];
    float x = event->pos().rx();
    float y = event->pos().ry();
    GLfloat  z = ;
    double winx, winy, winz;
    qDebug("Window coords are (%d, %d)\n", x, y);
    /*Read the projection, modelview and viewport matrices using the glGet functions.*/
    glGetIntegerv( GL_VIEWPORT, viewport );
    glGetDoublev( GL_MODELVIEW_MATRIX, modelview );
    glGetDoublev( GL_PROJECTION_MATRIX, projection );

//Read the window z value from the z-buffer

glReadBuffer(GL_FRONT);
glReadPixels( x, viewport[, GL_DEPTH_COMPONENT, GL_FLOAT, &z );

//Use the gluUnProject to get the world co-ordinates of
    //the point the user clicked and save in objx, objy, objz.
    gluUnProject( x, viewport[]-y, z, modelview, projection, viewport, &objx, &objy, &objz );
    qDebug("World coords at z=%.1f are (%.3f, %.3f, %.3f)\n", z, objx, objy, objz);

updateGL();
}

void GLWidget::draw()
{
    glPushMatrix();
    glBegin(GL_QUAD_STRIP);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glEnd();
    glBegin(GL_QUAD_STRIP);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glColor3f(.0f);
    glEnd();
    glPopMatrix();
}

/*---------------------------------------------------------------------------*/
void GLWidget::DrawFloor()
{
    glDepthMask(GL_FALSE);
    glColor4ub();
    glBegin(GL_LINES);

glNormal3d();
    )
    {
        glVertex3i(i, , -s_Scale);
        glVertex3i(i, , s_Scale);
        glVertex3i(-s_Scale, , i);
        glVertex3i(s_Scale, , i);
    }
    glEnd();
    glDepthMask(GL_TRUE);
}
/*---------------------------------------------------------------------------*/
void GLWidget::DrawAxis( void )
{
    // Local Space
;

glPushAttrib( GL_LINE_BIT );
glLineWidth(.0f );
glBegin( GL_LINES );

// X轴
);
glVertex3i( );
glVertex3i( s_Scale, );

// Y轴
);
glVertex3i( );
glVertex3i( );

// Z轴
);
glVertex3i( );
glVertex3i( , s_Scale );

glEnd( );
glPopAttrib( );
}

OpenGL 获取当前屏幕坐标的三维坐标（gluUnProject使用例子 Qt）-LMLPHP

代码仅供参考，最近一直在研究这个，用于实现场景中单个对象的拖拽，效果还欠佳，欢迎交流讨论。