QT OpenGL ubuntu下运用gluPickMatrix模式获取指定的点或线

「爱情、让人受尽委屈。」 2024-02-19 18:49 39阅读 0赞

**widget.h:**

\#ifndef WIDGET\_H  
\#define WIDGET\_H

\#include <QtOpenGL/QtOpenGL>

class Widget : public QGLWidget  
\{  
Q\_OBJECT

public:  
Widget(QWidget \*parent = 0);  
void draw();  
int faceAtPosition(const QPoint &pos);

protected:  
void initializeGL();  
void resizeGL(int width, int height);  
void paintGL();  
void mouseDoubleClickEvent(QMouseEvent \*event);  
\};

\#endif // WIDGET\_H

**widget.cpp:**

\#include "widget.h"  
\#include <QMouseEvent>  
\#include <GL/glu.h>

Widget::Widget(QWidget \*parent)  
: QGLWidget(parent)  
\{  
setFormat(QGLFormat(QGL::DoubleBuffer | QGL::DepthBuffer));  
\}

void Widget::initializeGL()  
\{  
qglClearColor(Qt::black);  
glShadeModel(GL\_FLAT);  
glEnable(GL\_DEPTH\_TEST);  
glEnable(GL\_CULL\_FACE);  
\}

void Widget::resizeGL(int width, int height)  
\{  
glViewport(0,0,width,height);  
glMatrixMode(GL\_PROJECTION);  
glLoadIdentity();  
GLfloat x = GLfloat(width) / height;  
glFrustum(-x,+x,-1.0,+1.0,4.0,15.0);  
glMatrixMode(GL\_MODELVIEW);  
\}

void Widget::paintGL()  
\{  
glClear(GL\_COLOR\_BUFFER\_BIT | GL\_DEPTH\_BUFFER\_BIT);  
draw();  
\}

void Widget::draw()  
\{  
GLfloat P1\[2\]\[3\] = \{0.0, -1.0, +2.0, +1.73205081, -1.0, -1.0\};

glMatrixMode(GL\_MODELVIEW);  
glLoadIdentity();  
glTranslatef(0.0, 0.0, -10.0);

int i;  
for (i = 0; i < 2; i++)  
\{  
glLoadName(i);

glBegin(GL\_POINTS);

glVertex3f(P1\[i\]\[0\], P1\[i\]\[1\], P1\[i\]\[2\]);

glEnd();  
\}

glLoadName(2);  
glBegin(GL\_LINES);

glVertex3f(P1\[0\]\[0\], P1\[0\]\[1\], P1\[0\]\[2\]);  
glVertex3f(P1\[1\]\[0\], P1\[1\]\[1\], P1\[1\]\[2\]);

glEnd();  
\}

void Widget::mouseDoubleClickEvent(QMouseEvent \*event)  
\{  
int name = faceAtPosition(event->pos());  
qDebug("selected: %d", name);  
\}

int Widget::faceAtPosition(const QPoint &pos)  
\{  
const int MaxSize = 512;  
GLuint buffer\[MaxSize\];  
GLint viewport\[4\];  
makeCurrent();  
glGetIntegerv(GL\_VIEWPORT, viewport);  
glSelectBuffer(MaxSize, buffer);  
glRenderMode(GL\_SELECT);  
glInitNames();  
glPushName(0);  
glMatrixMode(GL\_PROJECTION);  
glPushMatrix();  
glLoadIdentity();  
gluPickMatrix(GLdouble(pos.x()), GLdouble(viewport\[3\] - pos.y()), 15.0, 15.0, viewport);  
GLfloat x = GLfloat(width()) / height();  
glFrustum(-x, x, -1.0, 1.0, 4.0, 15.0);  
draw();  
glMatrixMode(GL\_PROJECTION);  
glPopMatrix();  
if(!glRenderMode(GL\_RENDER))  
return -1;

return buffer\[3\];  
\}

**main.cpp:**

\#include "widget.h"  
\#include <QApplication>

int main(int argc, char \*argv\[\])  
\{  
QApplication a(argc, argv);  
Widget w;  
w.show();

return a.exec();  
\}

**testPick.pro文件：**

QT += core gui opengl  
greaterThan(QT\_MAJOR\_VERSION, 4): QT += widgets  
TARGET = testPick  
TEMPLATE = app  
DEFINES += QT\_DEPRECATED\_WARNINGS  
SOURCES += main.cpp\\  
widget.cpp  
HEADERS += widget.h  
FORMS += widget.ui  
LIBS += -lglut -lGLU

**我们在两个顶点和画线的时候分别 glLoadName(i)，最后在双击的时候就可以找到端点和线的标识：**  
![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3I3NzY4Mzk2Mg_size_16_color_FFFFFF_t_70][]

**测试结果：**

![20190310143310620.png][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3I3NzY4Mzk2Mg_size_16_color_FFFFFF_t_70]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/2c8c75bb59344e22800f8c026613a58e.png
[20190310143310620.png]: https://image.dandelioncloud.cn/pgy_files/images/2024/01/29/9d62a5a8f18047229fe949a23eae96ce.png