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( 640 , 480 ); 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 = 0 ); ~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> static const qint32 s_Scale = 8 ; GLWidget::GLWidget(QWidget *parent) : QGLWidget(parent) { objx = 0 . 0 ; objy = 0 . 0 ; objz = 0 . 0 ; } GLWidget::~GLWidget() { } void GLWidget::initializeGL() { glClearColor( 0 . 0 , 0 . 0 , 0 . 0 , 0 . 0 ); glClearDepth( 1 . 0 ); glEnable(GL_DEPTH_TEST); glDepthFunc(GL_LEQUAL); } void GLWidget::resizeGL( int w, int h) { int viewport[ 4 ]; glViewport( 0 , 0 , w, h ); glGetIntegerv( GL_VIEWPORT, viewport ); glMatrixMode( GL_PROJECTION ); glLoadIdentity( ); gluPerspective( 45 , 1 . 33 , 0 . 1 , 400 ); double projection[ 16 ]; glGetDoublev( GL_PROJECTION_MATRIX, projection ); glMatrixMode( GL_MODELVIEW ); glLoadIdentity( ); gluLookAt( 0 , 10 , 10 , 0 , 0 , 0 , 0 , 1 , 0 ); } void GLWidget::paintGL() { glClear( GL_DEPTH_BUFFER_BIT | GL_COLOR_BUFFER_BIT ); //The big gray floor like polygon glBegin( GL_POLYGON ); glColor3f( 0 . 5 , 0 . 5 , 0 . 5 ); glVertex3f( - 10 , 0 , 10 ); glVertex3f( - 10 , 0 , - 10 ); glVertex3f( 10 , 0 , - 10 ); glVertex3f( 10 , 0 , 10 ); glEnd( ); //DrawFloor(); DrawAxis(); //The red cube to be drawn at clicked position glPushMatrix( ); glTranslatef(objx, objy, objz ); draw(); double modelview[ 16 ]; glGetDoublev( GL_MODELVIEW_MATRIX, modelview ); glPopMatrix( ); } void GLWidget::mousePressEvent(QMouseEvent *event) { updateGL(); double modelview[ 16 ], projection[ 16 ]; int viewport[ 4 ]; float x = event->pos().rx(); float y = event->pos().ry(); GLfloat z = 0 ; 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[ 3 ]-y, 1 , 1 , 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[ 3 ]-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( 1 , 0 , 0 ); glVertex3f( 0 .0f, 0 .0f, 0 .0f); glColor3f( 1 , 1 , 0 ); glVertex3f( 0 .0f, 1 .0f, 0 .0f); glColor3f( 0 , 1 , 0 ); glVertex3f( 1 .0f, 0 .0f, 0 .0f); glColor3f( 0 , 1 , 1 ); glVertex3f( 1 .0f, 1 .0f, 0 .0f); glColor3f( 1 , 0 , 0 ); glVertex3f( 1 .0f, 0 .0f, - 1 .0f); glColor3f( 1 , 1 , 0 ); glVertex3f( 1 .0f, 1 .0f, - 1 .0f); glColor3f( 0 , 1 , 0 ); glVertex3f( 0 .0f, 0 .0f, - 1 .0f); glColor3f( 0 , 1 , 1 ); glVertex3f( 0 .0f, 1 .0f, - 1 .0f); glColor3f( 1 , 0 , 0 ); glVertex3f( 0 .0f, 0 .0f, 0 .0f); glColor3f( 1 , 1 , 0 ); glVertex3f( 0 .0f, 1 .0f, 0 .0f); glEnd(); glBegin(GL_QUAD_STRIP); glColor3f( 0 , 0 , 1 ); glVertex3f( 0 .0f, 0 .0f, 0 .0f); glColor3f( 1 , 0 , 1 ); glVertex3f( 1 .0f, 0 .0f, 0 .0f); glColor3f( 0 , 1 , 0 ); glVertex3f( 0 .0f, 0 .0f, - 1 .0f); glColor3f( 1 , 0 , 0 ); glVertex3f( 1 .0f, 0 .0f, - 1 .0f); glColor3f( 1 , 1 , 0 ); glVertex3f( 0 .0f, 1 .0f, 0 .0f); glColor3f( 1 , 0 , 1 ); glVertex3f( 1 .0f, 1 .0f, 0 .0f); glColor3f( 0 , 0 , 1 ); glVertex3f( 0 .0f, 1 .0f, - 1 .0f); glColor3f( 1 , 0 , 0 ); glVertex3f( 1 .0f, 1 .0f, - 1 .0f); glEnd(); glPopMatrix(); } /*---------------------------------------------------------------------------*/ void GLWidget::DrawFloor() { glDepthMask(GL_FALSE); glColor4ub( 175 , 175 , 175 , 255 ); glBegin(GL_LINES); glNormal3d( 0 . 0 , 1 . 0 , 0 . 0 ); for (qint32 i = -s_Scale; i <= s_Scale; i += s_Scale >> 3 ) { glVertex3i(i, 0 , -s_Scale); glVertex3i(i, 0 , s_Scale); glVertex3i(-s_Scale, 0 , i); glVertex3i(s_Scale, 0 , i); } glEnd(); glDepthMask(GL_TRUE); } /*---------------------------------------------------------------------------*/ void GLWidget::DrawAxis( void ) { // Local Space static const qint32 s_Scale = 64 ; glPushAttrib( GL_LINE_BIT ); glLineWidth( 1 .0f ); glBegin( GL_LINES ); // X轴 glColor3ub( 255 , 0 , 0 ); glVertex3i( 0 , 0 , 0 ); glVertex3i( s_Scale, 0 , 0 ); // Y轴 glColor3ub( 0 , 255 , 0 ); glVertex3i( 0 , 0 , 0 ); glVertex3i( 0 , s_Scale, 0 ); // Z轴 glColor3ub( 0 , 0 , 255 ); glVertex3i( 0 , 0 , 0 ); glVertex3i( 0 , 0 , s_Scale ); glEnd( ); glPopAttrib( ); } |
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。