Recently I want to write a gui application, and its appearance is shown below:
I used MFC before to write normal gui applications, but I have never used qt to write gui applications. But this time I want to use qt, so i'm wondering is there any way to implement such interface, integrating with opengl and opencv subwindows within one application.
Please give me some directions on:
1. Which kind of widget can I draw opengl and opencv subwindows in my application?
2. Is there any way to do event handling in those subwindows respectively?
3. How does qt support for opengl and opencv integration?
There should be no problem.
In fact, I've used openCV and OpenGL in different projects, but I don't see any problem.
You have to convert opencv cv::Mat to QImage (see various posts on the problem on StackOverflow) and then draw on a QLabel or a subclass of it.
For openGL there are special classes: http://qt-project.org/doc/qt-5/qtgui-index.html#opengl-and-opengl-es-integration
You should use event handling as usual in Qt (signal-slot, you know).
Related
I'm creating an application, which interacts with OpenGL via QOpenGL* classes. The graphics is shown through a QOpenGLWidget, which is placed in a UI-form.
Now, there is a library for CAD purposes (Open CASCADE), an OpenGL interface of which requires a handle to the render window. The question is: can I somehow say the library to render everything to the mentioned widget?
In other words, is there a way to interpret the widget as a native, probably, platform-specific (HWND here) window, so that the library renders its own stuff exactly there?
Thanks
QOpenGLWidget is not the same thing as QGLWidget.
The classical approach for embedding OCCT 3D viewer, which you can find in Qt IESample coming with OCCT, creates QWidget with unique window handle flag, takes this window handle and ask OCCT to take care about OpenGL context creation for this window. This is most straightforward, robust and portable way with one limitation - Qt will not be able drawing semitransparent widgets on top of this QWidget. This is not a limitation of OCCT, but rather limitation of Qt Widgets design.
QOpenGLWidget was intended to solve this limitation by allowing to mix custom OpenGL rendering and normal widgets. The integration of external OpenGL graphics engine, however, became more complicated and fragile. It is not very helpful stealing winId() from QOpenGLWidget, as rendering content is expected to be drawn not into window itself, but rather into OpenGL framebufer object (FBO), created by QOpenGLWidget - see QOpenGLWidget::defaultFramebufferObject() property.
External renderer is expected to render into this FBO for proper composition of Qt widgets. Luckily, OCCT is flexible enough to allow such integration. Unluckily, such integration requires some knowledge of OpenGL, as well as its usage by Qt and OCCT.
For that, you need to ask OCCT wrapping OpenGL context already created by Qt (for that V3d_View::SetWindow() provides an optional argument of type Aspect_RenderingContext, which corresponds to HGLRC on Windows and can be fetched using wglGetCurrentContext() within rendering thread) as well as FBO created by QOpenGLWidget (for that, OCCT provides OpenGl_FrameBuffer::InitWrapper() and OpenGl_Context::SetDefaultFrameBuffer() methods, as well as OpenGl_Caps::buffersNoSwap flag to leave window buffer swapping management to Qt).
OCCT doesn't come yet with a sample using QOpenGLWidget, but you can find also qt/AndroidQt sample implementing similar thing for embedding OCCT 3D Viewer into QtQuick application.
After some investigation, I found that method QOpenGLWidget::winId() returns the correct handle. It's been found out only now, because the rendered scene disappeared immediately, leaving a black picture instead. However, when the viewport is resized, the scene returns back (and disappears again, though). Looks like Open CASCADE has problems with Qt 5 OpenGL implementation, since QGLWidget didn't have such problems, as far as I know.
I need to create a GUI with a file menu and menu in which the user can input parameters. The parameters are then used for drawing rectangles in a canvas which is part of the application window. Is there a way to scale the OpenGL subwindow to just one part of the screen and the parameter input to the other? The application needs to be written in C++.
Is it possible to create a GUI with QT and draw the rectangles in the same window using OpenGL? If not, what is the common way to integrate a GUI with OpenGL? (or any other graphics library which I can use to draw rectangles from points as easy as possible)
EDIT: I am not sure If OpenGL is necessary or there is a way to paint the rectangles on the canvas like you can in Java with paintComponent().
I have never used QT before so I am not aware of its capabilites.
you can use opengl window singly or use this in the common mainwindow. previous example (in first answer) show how to use opengl window in qt singly and without communication with other components of Qt (like menu, toolbar and ...). but you can add a opengl window to a mainwindow (like other widget) and use it alongside other widgets . this example can help you.
Yes, using OpenGL together with Qt is absolutely possible. There is even an example for that and Qt provides classes for a more object oriented way of using OpenGL. Have a look here (Section "OpenGL and OpenGL ES Integration") for more details.
I am new to Qt and I want to use Qt to make interactive geometry programs using CGAL. I would like the user to input, say points, segments, using the mouse and then push a button to get a CGAL algorithm working on the input.
My environment is CGAL 4.5, Qt 5.6 and QtCreator 3.6.1 on an Ubuntu 14.04 machine.
CGAL has builtin support for its objects to be
rendered using the QtGraphicsViewFramework (http://doc.cgal.org/latest/GraphicsView/index.html )
I don't know how to render CGAL objects -- points, lines, rays, polygons -- onto a Qt window. The page I linked to above assumes a knowledge of Qt to get an application working, and so is not helpful to a Qt beginner.
Thus far, I have created a Qt widgets application project using QtCreator. From what I know, I need to modify the mainwindow.ui file graphically inside QtCreator by dragging and dropping different kinds of widgets onto it and then map signals calling CGAL functions onto slots of whatever the drawing canvas widget will be. (Is this correct? I am shaky on the signals and slots mechanism)
MY QUESTION IS....which widget do I place onto the window as a drawing canvas? Two relevant widgets seem to be GraphicsView and OpenGL widgets
under the DisplayWidgets menu. But how do I use them?
I have no CGAL experience, but I can give you some Qt-related hints:
Use the QGraphicsView + QGraphicsScene. If you want, you can enable OpenGL support like this:
QGraphicsView view = new QGraphicsView(parentWindow);
view->setViewport(new QOpenGLWidget(view));
To draw CGAL objects you have to use either provided graphics item classes (CGAL::Qt::TriangulationGraphicsItem, CGAL::Qt::VoronoiGraphicsItem, ...) or derive your own from the CGAL::Qt::GraphicsItem. To add an item to the scene, use the QGraphicsScene::addItem() method.
To navigate (pan + zoom) the view, CGAL provides the CGAL::Qt::GraphicsViewNavigation class. This is how to use it:
CGAL::Qt::GraphicsViewNavigation* navFilter = new CGAL::Qt::GraphicsViewNavigation(view);
view->viewport()->installEventFilter(navFilter);
I'm trying to develop a cross platform (or at least desktop + embedded hardware) application. I would like to use Qt Quick to create a touch friendly GUI. I have been implemented a classical application with a QGLWidget displaying data. It is important that only a part of the window is in OpenGL. Because of this there are problems with EGLFS and LinuxFB. Only X11 (or maybe Wayland) can display the application properly (others generates a couple of errors about missing setParent function and the whole screen is black). Now I'm trying to achieve the same thing in QML. I want to use this OpenGL renderer as part of my QML application and some Qt Quick widgets around it. I found a couple of people asking about the same thing and the answer is always to subclass QDeclarativeItem and call the painter's beginNativePainting() (the others says to export it through QDeclarativeItem, but I cannot figure out how to do this). The problem is that on desktop, Qt 5.11 the native painter is not OpenGL. And in QT5 there is no way to force OpenGL graphics system. So when I try to get the OpenGL context (QGLContext::currentContext()) I always get NULL. Another problem: If I export my widget with qmlRegisterType("Test", 1, 0, "Test"); it becomes only visible when I use QDeclarativeView, but then it doesn't sees Qt Quick. If I use QQuickView it says module "Test" is not installed. How can I implement this properly?
QDeclarativeItem is from Qt Quick 1 and Qt4. With Qt 5 and Qt Quick 2 you should use QQuickItem.
There is at least 1 example of this provided with qt docs, which you can find in Qt Creator in the Welcome tab in the Examples section.
I am writing a program in OpenGL and I need some sort of interfacing toolbar. My initial reactions were to use a GUI, then further investigation into C++ I realized that GUI's are dependent on the OS you are using (I am on Windows). Therefore, I decided to use QT to help me.
My Question is if I am taking the best/appropriate approach to this solution. Am I even able to write my OpenGL program and have the GUI I want to create interface with the C++ code to do what I want it to do.
For example, If I create a simple "control panel" with arrows in each direction. And on screen I have a box object created by glut can I interface the arrows to be clicked on and interact with the openGL program to move the box?
Using Qt is coherent for your problem: it provides good integration of OpenGl through the QtOpenGL module.
Derive your display classes from QGLWidget (until Qt 4.8) or from QOpenGLWidget (since Qt 5.4) and implement virtual methods paintGL() etc.
You will have access to the Qt's signal and slot system so that you will be able to catch Gui events and update the OpenGl display.
You can use regular non-OpenGL Qt widgets on top of a QGLWidget so what you describe is do-able.
One thing I came across when doing this was that the regular widgets had to be opaque. The moment they were transparent in any way there was all sorts of garbage underneath them. That was a while ago so maybe the latest version addresses this issue. May have been platform-specific too so YMMV.
Stay in GLUT. There's no need to add Qt for a control panel. You could open a sub window (or second window, whichever works better for your program design), and draw the controls into that window, and use GLUT to handle the mouse interaction.
Furthermore, Qt and GLUT each have their own event loops. To use just Qt's event loop, you'd have to abandon much of the GLUT structure, since the GLUT event loop would not be there to call your callback functions. Qt does have the functionality to have let somebody else event loop call Qt's event processing code, but I don't think there's an easy way to make GLUT hand off the event information.