How to update a OpenGL GLWidget embedded within QT?

[sonda]

Hi everyone!
I am developing a really simple application using QT and OpenGL. The application contains a few buttons for interaction and a widget tab containing 3 pages, the first two for analysing and processing some data and the third contains a GLWidget which should draw the result points in a 3d space.
At the beginning the 3d space doesn't contain any points and after all the data are processed it should draw the 3 points.
So far I have tried to call an external function to paintGL() to draw a solid cube at the centre of the scene. The method is correctly called but the widget does not display any cube.
If you want I can post part of the code and if you have any questions then please do not hesitate to ask me.
I hope someone of you can help me with this.

[wysota]

Just call update() on the widget.

[sonda]

I have tried but it doesn't work, so I decided to post my code.

glwidget.cpp


GLWidget::GLWidget(QWidget *parent) :
QGLWidget(parent)
{
connect(&timer, SIGNAL(timeout()), this, SLOT(updateGL()));
timer.start(1000);
}

void GLWidget::initializeGL(int w, int h) {
glClearColor(0.2f, 0.2f, 0.2f, 1);
glViewport(0, 0, w, h);
// Setup light
const GLfloat light_ambient[] = { 0.0f, 0.0f, 0.0f, 1.0f };
const GLfloat light_diffuse[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_specular[] = { 1.0f, 1.0f, 1.0f, 1.0f };
const GLfloat light_position[] = {2.0f, 5.0f, 5.0f, 0.0f };
glEnable(GL_DEPTH_TEST);
glEnable(GL_CULL_FACE);
glEnable(GL_DOUBLE);
glShadeModel(GL_SMOOTH);
glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
glEnable(GL_DEPTH_TEST);
glEnable(GL_LIGHT0);
glEnable(GL_LIGHTING);
glEnable(GL_COLOR_MATERIAL);
glLightfv(GL_LIGHT0, GL_AMBIENT, light_ambient);
glLightfv(GL_LIGHT0, GL_DIFFUSE, light_diffuse);
glLightfv(GL_LIGHT0, GL_SPECULAR, light_specular);
glLightfv(GL_LIGHT0, GL_POSITION, light_position);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
glDepthFunc(GL_LESS);
glEnable(GL_COLOR_MATERIAL);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(60.0, 1.0, 0.0001, 1000.0);
glMatrixMode(GL_MODELVIEW);
current_view= TOP_VIEW;

}

/ Display
void GLWidget::paintGL() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glLoadIdentity();
setView();
if (current_view == EXPLORING_VIEW)
calculate_lookpoint();
gluLookAt(eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz);
// Draw axis and add points
drawAxis();
int ind;
Skyline s;
if (s.skylineGenerated()) {
drawCube();
cout << "Generated" << endl;
}
swapBuffers();
}

void GLWidget::drawCube(void){
cout << "Drawn\n";
glTranslatef(0.0,0.0,0.0);
glColor3f(1.0,0.0,0.0);
glutSolidCube(2.0);
update();
}

// Reshape
void GLWidget::resizeGL(int w, int h) {
glViewport(0, 0, (GLsizei) w, (GLsizei) h);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective (48.0, (GLfloat) w/(GLfloat) h, 10.0, 800.0);
glMatrixMode (GL_MODELVIEW);
}



Despite the fact I call update(), when I click on the tab containing this widget no cube is shown. Furthermore the light is not working. Can you please help me? Ah I have the entire Opengl program in a class and everything is working but I don't understand why the GLWidget is not working like the original program.

[wysota]

Your drawCube() doesn't make sense. If you want to draw something, you are supposed to call update() and draw what needs to be drawn in paintGL().

[sonda]

I have modified the code for paintGL() but this time everything (axis and cube) is rotating:


void GLWidget::paintGL() {
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_DEPTH_TEST);
glLoadIdentity();
setView();
if (current_view == EXPLORING_VIEW)
calculate_lookpoint();
gluLookAt(eyex, eyey, eyez, centerx, centery, centerz, upx, upy, upz);
// Draw axis and add points
drawAxis();
int ind;
Skyline s;
if (s.skylineGenerated()) {
glPushMatrix();
glTranslatef(0.0,0.0,0.0);
glColor3f(1.0,0.0,0.0);
glRotatef(0.5,1,0,1);
glSolidCube(2.0);
glPopMatrix();
update();
}
swapBuffers();
}


And why the light is not working?

[wysota]

You are not supposed to be calling update() from within paintGL(). The latter will be called by Qt as a result of the call to the former. Have you gone through at least one Qt OpenGL example?

[sonda]

Yes I have seen lots of examples. Anyway I have decided to use my original program and execute it within the GLWidget. So I added this line


void Sk::on_pushButton_clicked()
{

process.start("/home/user/Desktop/Test");

}


How can I display the external program within the GLWidget?

[wysota]

How can I display the external program within the GLWidget?
You can't.

[sonda]

But I have read about QX11embedContainer, I have tried to include the library but it gives me an error. So the only way to run that executable is to use an external window???

[wysota]

But I have read about QX11embedContainer, I have tried to include the library but it gives me an error.
QX11EmbedContainer requires "the other application" to know how to embed itself into a given X window.


So the only way to run that executable is to use an external window???
Basically yes.