I need an appropriate rendering engine to render a 3D model into Qt, and use Qt then as an event handler to this model. Thank you.
As for the rendering engine, you can go several directions, but I'll mention two. Qt comes with an OpenGL widget. You could make use of this by either:
writing your own rendering code to render your model using OpenGL
or
making use of a rendering engine/framework which has it's own Qt Widget (possibly derived from Qt's OpenGl widget). I know OpenSceneGraph has Qt integration available. And I seem to remember Ogre does as well. This just to mention two options. Just Google for Qt and your favorite engine and you'll most likely find something suitable. And if not, it is usually not that difficult to write your own integration if you feel like it.
Whichever option is more suitable for you depends on the exact specification of what you're trying to achieve. You probably know that better than we do.
As for the event handling, you might want to be a bit more specific as to what you mean.
Related
Is there any way to use your own custom GLSL shaders with JavaFX? I am currently using Java 8 162 and find that there is a serious lack of JavaFX 3D documentation.
Is there any way to use your own custom GLSL shaders with JavaFX?
No. GLSL shaders are compiled at runtime and are bound to the OpenGL graphics pipeline, which is internal. There was a request for this in the past, but no one put in the work for it.
You might be able to hack something in if you build JavaFX locally. It depends on how extensive the changes you want to make are. You can add shaders like the one in modules/javafx.graphics/src/main/resources/com/sun/prism/es2/glsl/main1Light.frag (and main2Lights and main3Lights). You will then need to change com.sun.prism.es2.ES2PhongShader accordingly, at the very least.
What shader are you trying to make? Maybe it can be built into JavaFX if it's reasonable.
there is a serious lack of JavaFX 3D documentation
Yes. Many internal classes have "TODO: 3D - Need documentation" comments on them too. I suggest that you write to the mailing list a request for what documentation you would like to see exactly.
I've just started learning Qt recently, finding QML quite interesting for implementing UI component. Before the project really kick off, I've got some questions:
For a fresh start project, should I just use QML? Does QML be designed for replacing QWidget?)
If I go with QML, is there anything else must be implemented with C++? Or better implemented with C++ for better performance? (I know some customized UI components can be integrated through plugin) What's the relationship between QML and C++ widget?
As for performance or rendering issue, does QML better than native C++ widget?
When you start a question with 'Should I use', it is quite a good hint that SO might not be the right place to ask it. Even more when there are only answers, which start with 'It depends on...'.
QML is not designed to replace QWidget. It is a different technique. Which one to use, depends on your requirements.
Whether or not you must implement additional stuff in C++ depends on your project. Some things are easier in C++, others in QML. And some stuff is not possible in QML at all.
There is no relationship between QML and C++ widgets.
And the performance of QML is in most cases more than sufficient. In almost every case QML is used to create user interfaces. I doubt that there are many cases where clicking a button or opening a dropbox folder is performance critical.
I had a chance to put this question to a few Qt experts at the World Summit today and the general take was that because QML component rendering can be done through hardware acceleration that it is preferred for apps requiring high performance graphics, eg automotive dashboards. OTOH widgets seem to be used for desktop applications. Another consideration is that while widgets can be styled using Qss (Qt's version of Css), QML components cannot.
In QML based applications computationally intensive functions are generally written in C++.
HTH,
Eric G
New to Qt. In the official Qt tutorial, it says:
To set up a project, you first have to decide what kind of an application you want to develop: do you want a user interface based on Qt Quick or HTML5 or Qt widgets.
We plan to use Qt to do medical image display, and also use Qt to build a GUI application to control a medical device. They will be two different projects.
Which Qt project type we should use for them?
Docs say:
QWidgets are a better choice if your UI is comprised of a small number of complex and static elements, and QML is a better choice if your UI is comprised of a large number of simple and dynamic elements.
I say:
If you're going for desktop applications I'd suggest Qt Widgets, you don't have to ship the final app with libs for QML and the whole source will be written in C++ (faster, simplier so easier to debug).
QML would be a nice alternative if you want to create phone/tablet (touch experience in general).
I would argue that between Qt Quick and Qt Widgets there is no objectively right answer. In theory, one should be able to replicate any UI using either method - because at the end of the day, they are both using QtGui behind the scenes. So functionality is probably not an issue.
One thing to note is that Qt Quick (i.e., QML) is designed explicitly to make UI programming require much less code, and much less C++ knowledge. I would say it achieves this goal very well.
However, at the end of the day, I think it mostly comes down to what language your developers are already familiar with. If you have a team of C++ pro's, then I would go with Qt Widgets - if only because it's going to be very easy for them to pick up, and it's something they're already familiar with. (I'm guessing this is the case because you're already writing C++ code for your project).
If, on the other hand, your developers are already very good at QML (or, more generally, JavaScript - which QML is heavily influenced by), then I would go with Qt Quick for the same reasons.
I know of two types of Qt UI: Qt Quick and widgets.
Widgets behave like most other UI toolkits out there, you have a GUI editor and a tree of UI objects. They are pretty mature and look like most standard UIs.
Qt Quick is the newer Qt UI toolkit. It uses a domain specific declarative language (QML) to specify the user interface and JavaScript for interactions. There are also plans to offer Qt widgets inside the Qt Quick framework, but I'm not sure how far that project has gotten. Qt Quick is meant to deliver more dynamic / custom user interfaces.
As far as I know Qt will continue to support both approaches in the foreseeable future so which one you pick depends on your use-case.
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
Every time I start a project with some graphical toolkit, one of the first conflicts happen with the decision of how to deal with the visual design and the widget layout: A graphical tool or handcoding?
This is a quite tricky/subjective question because most people will decide based on personal preference. It also depends greatly on the quality of the graphical tool. In this case I would like to focus just on the latest version of the QT library. I do not intend to discuss which method is better. I am convinced that the best answer is: depends on the project.
What I want is a reference to a good non biased article, based on experience after several projects. The article should just describe the tradeoffs of both choices
I started with doing everything hand-coded, and of late have been switching to using Qt Designer for most forms. Here are some benefits for each position:
Using Qt Designer
The biggest time saver for me is managing complex layouts; it saves a lot of tedious coding. Simply (very roughly) arrange your widgets, select them, right-click, and put them in the correct type of layout. Especially as layouts become nested, this is so much easier.
It tends to keep your implementation files cleaner instead of filling them with all the boilerplate layout code. I'm type-A, so I like that.
If you are translating your application, it is possible to send your translators the .ui files so they can see on your GUI where the text they are translating will be. (Assuming they are using Qt Linguist.)
Hand-coding
Control. If you have a layout where you need to instantiate / initialize the controls in a very particular order, or dynamically create the controls based on other criteria (database lookup, etc.), this is the easiest way.
If you have custom widgets, you can kind-of-sort-of use the Designer, adding the closest built-in QWidget from which your class derived and then "upgrading" it. But you won't see a preview of your widget unless you make it a designer plugin in a separate project, which is way too much work for most use cases.
If you have custom widgets that take parameters in their constructor beyond the optional QWidget parent, Designer can't handle it. You have no choice but to add that control manually.
Miscellaneous
I don't use the auto-connect SLOTS and SIGNALS feature (based on naming convention such as "on_my_button_clicked".) I have found that I almost invariably have to set up this connection at a determinate time, not whenever Qt does it for me.
For QWizard forms, I have found that I need to use a different UI file for each page. You can do it all in one, but it becomes very awkward to communicate between pages in any kind of custom way.
In summary, I start with Qt Designer and let it take me as far as it can, then hand-code it from there. That's one nice thing about what Qt Designer generates--it is just another class that becomes a member of your class, and you can access it and manipulate it as you need.
My answer is based on two years developing biochemistry applications using PyQt4 (Python bindings to Qt 4) and OpenGL. I have not done C++ Qt, because we only used C++ for performance-critical algorithms. That said, the PyQt4 API greatly resembles Qt4, so much here still applies.
Qt Designer
Good
Exploration. Discover what widgets are available, the names for those widgets, what properties you can set for each, etc.
Enforces separation of UI logic from application logic.
Bad
If you need to add or remove widgets at run-time, you have to have that logic in code. I think it's a bad idea to put your UI logic in two places.
Making changes to nested layouts. When a layout has no widgets in it, it collapses, and it can be really hard to drag and drop a widget in to the location you want.
Hand coding
Good
Fast if you are very familiar with Qt.
Best choice if you need to add or remove widgets at run-time.
Easier than Qt Designer if you have your own custom widgets.
With discipline, you can still separate UI layout from behavior. Just put your code to create and layout widgets in one place, and your code to set signals and slots in another place.
Bad
Slow if you are new to Qt.
Does not enforce separation of layout from behavior.
Tips
Don't just jump into creating your windows. Start by quickly sketching several possible designs, either on paper or using a tool like Balsamiq Mockups. Though you could do this in Qt Designer, I think it is too tempting to spend a lot of time trying to get your windows to look just right before you've even decided if it is the best design.
If you use Qt Designer for PyQt, you have the extra step of running pyuic4 to compile your *.ui files to Python source files. I found it easy to forget this step and scratch my head for a second why my changes didn't work.
If you code your UI by hand, I suggest putting your layout code in one place and your signals and slots in another place. Doing this makes it easier to change the way your widgets are arranged on a window without affecting any of your application logic. Or you can change some behavior without having to wade through all the layout code.
Enjoy Qt! Now that I am using Java Swing for work, I miss it.
I tend to layout dialogs using the designer but I do all the event handling stuff in the main code. I also do all the main windows, toolbars, menus in direct code.
The designer is just frustrating - a pity since decent drag and drop sizer based designers have been around for more than a decade
It depends on the number of different windows/panels you need for your application. If the number is small, use a graphical tool. It is much faster to get a few windows designed perfectly. If the number is large, the graphical tool can (and should) only be used for prototypes. You need to code the layout to be able to make application-wide changes at acceptable cost.
That includes creating a model of how the UI of the application works and dynamically adding and removing widgets at runtime. For an excellent example of such a model (in a different environment), take a look at the glamour model for creating object browsers.
I object to the suggestion that it is tricky/subjective (at least more than other development choices). It is easy to come up with criteria to decide on. Personal experience and preference are important for that, as they decide when the number of different windows should be considered small. The same goes for tool quality.
My personal opinion (just personal), all GUI based development distracts me too much, my imagination or my mind works very bad when i'm seeing gui objects, i prefer to hand-coding most the time because my imagination works better, you know, is like you were reading a book with no images... when i see nothing else than code its looks like i finish faster...
Second reason, i like c++ so much, so I see the good side of hand-coding, is that I keep my c++ practice no matter if I'm writing something redundant... Coding skill is improved when you only use text... Indeed, i could use nano or vim, but that is too far slow for debuging.
Hand-coding here ++vote
I use a combination of both:
I find for x,y coordinates, Designer is the way to go.
A lot of the other UI properties etc can be set in your code.
I think trying to do UI completely by hand-coding would be a very time consuming project. It's not as simple as setting up HTML tables.
Yes version 4 is bad, but people at work who have used version 3 said it was REALLY bad. Lots of crashing.
I, along with my fellow QTers, are truly hoping that version 5 will be an improvement.
I know this is an old question, but I hope this helps! One man's experience.