I know that a classic way of displaying OpenGL elements inside (Py)Qt is to override the QGLWidget.paint() method to make direct OpenGL calls.
However, does anyone know of a lib I could use to avoid making direct calls to OpenGL? Something that would, for example, load an image or video frame to a textured triangle strip in a single call? Or any kind of OpenGl video lib that I could integrate with PyQt?
My final goal is to display OpenGL video inside a PyQt window.
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I am working on OpenGL to create a GUI .I want to create some tabs which will help me to display different things in different windows. How is this possible using OpenGL? I read in some articles that we can use QT for that. Since I have already developed some of the GUI part in OpenGL using GLUT library ,is it possible to use the same code in QT? If so brief me how to make settings for OpenGL libraries in QT creator.
In my GUI I am trying to create a Car which is following a track.
I think you might be mixing some things up: OpenGL is a API with which you can instruct drivers to draw visual primitives, like lines, boxes, 3D triangles, pictures from buffer onto a render plane.
GLUT is a library that gives you a minimal environment around that, ie. it handles creating a window etc.
Neither of them are high-level UI description tools. Qt is really most likely what you want, as it will not only give you things like tab widgets etc, but also a feature-rich framework to do things like defining what should happen when you click a button, close a window etc.
There's a lot of examples of OpenGL usage within Qt widgets. In fact, a lot of visualization frontends use Qt and OpenGL. Qt has extensive documentation on how to generate OpenGL contextes and draw inside Qt applications.
I am not an expert but I have been using Qt/QtEmbedded for sometime now, for SBC 6845. I have created a few applications and have successfully run them on my device.
Now I want all of those applications to appear on a home screen. I understand that using QML/Qt Quick this might be achieved, but I don't have any idea on how to proceed with it. I have gone through some links and tutorials but most of them show how to create buttons and all that with Qt Quick, but not much than that. I am yet to find some tutorial/docs which can point me how to proceed with all applications on my home-screen. I need some directions, any links, advice on docs/books is welcome.
[While cross-compiling the QtEmbedded 4.6.2 libraries for my SBC I encountered problems with enabling opengl support. And, I am unaware of the other methods for using QtQuick2 without opengl.
The applications (5-6 of them) are QWidgets and linking icons require to stay in the home screen. I want to keep them as simple as possible without any effects for the icons.
Plainly speaking, I am trying to create a bunch of icons displayed on the home screen linked to those applications. The applications if launched in windows style application, (or like a popup QDialog) will also serve my purpose.]
Thanks.
"I have gone through some links and tutorials but most of them show
how to create buttons and all that with Qt Quick, but not much than
that"
For this part of the question, I'd advise you to download QtCreator
and start playing with the demos (using more than just some buttons:
you have demos for ListViews, GridViews, Delegates, Animations,
Particles, QtQuick Layouts (Qt5.1 only), QtQuick Controls (Qt5.1
only).
There's also the rather complete :
http://qt.gitorious.org/qt-labs/qt5-everywhere-demo
I'm completely unfamiliar with all the embedded/cross-compiling
aspects of your question.
About OpenGL/QtQuick2 : http://qt-project.org/forums/viewthread/30483
http://qt-project.org/forums/viewthread/17201
Also note that you can embed QtQuick2 scenes into a QWidget, but not
the other way around (no QtWidget inside the scenegraph).
So maybe the easiest/fastest way to go for you would be to stick with Qt4 or Qt5 declarative/QtQuick1 module (might be deprecated/removed starting with Qt 5.2). In this setup, there is no scenegraph/mandatory need for OpenGL. And you can embed QWidgets into your qml scene (no scenegraph: it uses the QGraphicsView backend) via QGraphicsProxyWidget.
You'd then have some GridView (you also could use some Grid with a Repeater) filled with models and delegates (= a delegate acts as a template item to be filled with the model).
Your delegates would have states/maybe Loader(s) (for on-demand loading) : icon state and when clicked, some maximized state containing a loader, loading your widget through QGraphicsProxyWidget.
You already have half of this presented in this example (a grid + 2 states : small icons grid and maximized view, you only need to implement the delegate/loading/model/QGraphicsProxyWidget things):
http://developer.nokia.com/Community/Wiki/Implementing_parent_change_animation_with_QML
I have been looking far and wide to find out how, if it’s possible, you can fill a particular area in a QML screen with an OpenGL context and do custom OpenGL only in that context. I’ve seen plenty of demos where the QML components like buttons, etc lay on top or below a screen-wide OpenGL context (as is typically required by games), but I’d like to be able to situate several distinct OpenGL contexts within QML and have the QML file define how large they are, where they are positioned, etc.
Now, since Qt 5 is all OpenGL under the hood, it makes me wonder if using a Canvas element with custom drawing via javascript could result in similar rendering performance as custom OpenGL? This would be a meaningful alternative but it’s not clear to me how the javascript drawing is handled via runtime compared to custom OpenGL drawing.
What is it that you want to draw? QQuickPaintedItem may be the simplest way to go about it. When you're using QOpenGLFramebufferObject as the target, the painter will use OpenGL to paint the texture. It might be easier than writing your own OpenGL code if all you're doing is 2D.
I have never done a Qt video application - newbie in this area. I have a custom video file format to render using Qt. The video file format is 256-byte header, then pixel data, then 256-byte header, then pixel data and so on.
The header consist info like width, height in pixels, bytes per pixels, frame rate etc and the pixel data is in Bayer (GBRG). I may have to process data before display - like convert to RGB (not sure yet). I see there are lot of video related classes like QGL*, QMovie, QVideo* ... don't know where to start ? I have seen mandelbrotwidget example which looks like a good place to start but still need some advice. Also, do I have to write a Qt Image plugin for Bayer pattern?
Thank you.
Good advice is to do all by yourself. If you have simple data structure read it by simple C++-code.
Conversation from Bayer RGB to RGB like here you can also make without using any Qt objects.
And now, when you'll got trivial RGB-image (even in your own structure) per frame, you can show it on widgets such as QGL* -- if you prefer OpenGL rendering, or Qt's classes such as QPainter, QImage...
Some more links: C++ GUI Programming with Qt4, 2nd Edition, Graphics View Framework
The best place to start is by learning the basics of custom drawing in Qt. In short, a very simple implementation would require you to:
Create a custom QWidget subclass
Override the paintEvent() method
Use a QPainter/QImage to decode your raw video data into image data and draw it on screen
Qt has lots of good sample code to get you started, such as:
http://qt-project.org/doc/qt-4.8/examples-painting.html
Once you have a simple implementation up and running, and a basic grasp of Qt concepts/classes, then you'll be ready to profile, optimize, and make use of more advanced Qt functionality (GL, video) as needed.
I have enabled qt+OpenGl+SimpleGl on one of the ARM platform and was able to run opengl example programs.
I also has a qt+Webkit, which is working with a graphic plugin.
I wanted to use simpleGl context for every thing, instead of using the normal graphic screen. So, when I try to run Qt+Webkit with simpleGl, I just get a blank screen.
Does QT support this? If so how can we make it?
Yes, this is correct. OpenGL draws directly to the framebuffer. The simplegl driver doesn't handle what is drawn using the raster paint engine of the QWS, so you may see only black.
Using simplegl for "everything" means you want everything to be drawn using OpenGL in your EGL full-screen window? This is possible under some assumptions. You have to write all your applications to be rendered using the Qt OpenGL paint engine (using the opengl graphics system is not supported under Qt/E). This is possible also for QtWebKit, I'm doing it now. Note that this does not mean that everything is rendered using hardware acceleration. You'll have to write your applications "the right way" to get all actually hardware accelerated. Consider that you'll have to handle the mouse pointer some other way in this case.
The other way is to just modify the simplegl driver to allow for the use of Qt applications using the raster paint engine. This is possible as well with some limitations. Qt can use blit to place its own windows over OpenGL. Look for the framebuffer driver inside the Qt source tree to know how to do this. You can then have common Qt applications and OpenGL Qt applications some way. I'm doing this as well. Not everything can be done anyway.
EDIT: I'm sure you already did, but in case, give this http://doc.qt.io/qt-4.8/qt-embeddedlinux-opengl.html much attention.
Unfortunately I don't know anything about SimpleGL, but I do know that there is a way to render a standard Qt widget in a QGLWidget. Maybe have a look at this Qt Quarterly which I think is somewhat related to your question:
http://doc.qt.nokia.com/qq/qq26-openglcanvas.html