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) ", 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) ", 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。