[solved] Qt and OpenGL
I'm trying to use the power of the OpenGL on a Colibri T20 from Toradex. The card is running Linux (Angstrom) with X11 (Xorg).
I've developped a small piece of code (which is running fine on Windows) with both QWidget and QGLWidget. It's a simple animation on a picture (fade-in/fade-out) When I'm running the version with the QWidget I can see my processor up to 20% and when I'm running it with the QGLWidget, the processor activity looks like the ECG from a reality TV star, so I concluded that my usage of the QGLWidget is correct. :-)
The problem is when I'm running the code on the card: the animation I've created is sloooooooooooooooooow (with both QGLWidget and QWidget)
So my question is: Am I really using the hardware accelaration or not? How can I test it? Should I have receive an error from my project during the compilation if OpenGL wasn't installed on the card? Or, is my code optimized? (my opinion: my code is not optimised at all :-) )
Here is the code of my test widget:
GLWidget::GLWidget(Helper *helper, QWidget *parent)
: QGLWidget(QGLFormat(QGL::SampleBuffers), parent), helper(helper)
elapsed = 1;
reverse = false;
//elapsed = (elapsed + qobject_cast<QTimer*>(sender())->interval()) % 1000;
elapsed = elapsed + 0.01;
elapsed = elapsed - 0.01;
if(elapsed <= 0 && reverse == false) reverse = true; else if(elapsed >= 1 && reverse == true) reverse = false; repaint();
void GLWidget::paintEvent(QPaintEvent *event)
helper->paint(&painter, event, elapsed);
And here the repaint's call
@GLWidget *openGL = new GLWidget(&helper, this);
QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), openGL, SLOT(animate()));
Thanks a looooooot!
Hi and welcome to devnet,
I'm not sure I'm following you right. Since you want to do OpenGL why are you using paintEvent ?
Also, you are trying to update at 100fps which might be a bit optimistic for an embedded board.
Thanks for welcoming me on the forum and for your answer!
I followed a tutorial on line to create this widget because I've never worked with OpenGL and paint functions. Should I use paintGL and QGLPainter instead?
I've try to turn down to 10fps, the result seems the same... For my fade-in/out functions, I'm using the painter's setOpacity function, is it the right way?
What I want to do is simple, just a smooth fade-in/out on a picture :-)
Thanks for you answer!
Then you might be overcomplicating things, what about this:
- QLabel -> for your image
- QGraphicsOpacityEffect -> self-explaining
- QPropertyAnimation -> to animate the QGraphicsOpacityEffect
This way everything is automated for you
Thanks, but actually I've started to use OpenGL directly because my first try was QPropertyAnimation and QGraphicsOpacityEffect and the result wasn't good too.
But, good news! I've found a solution... The problem was the picture it self... I used a too big one and because i'm lazy i downscaled the picture to see it entirely on the screen... So I've changed the picture by a picture of 1920x1080 and... Wow, at 100fps, it's smooth as hell! And it use only 5 to 8 percent of the processor!
Sorry for this thread... My fault... But I've learned a lot and maybe my code will be usefull for somebody else :-)
You're welcome !
Don't be afraid to ask question :)
Since you have it working now, please update the thread title prepending [solved] so other forum users may know a solution has been found :)