[solved] Qt and OpenGL

[Speechless]

Hi Guys!

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:

@#include "glwidget.h"
#include "QDebug"

GLWidget::GLWidget(Helper *helper, QWidget *parent)
: QGLWidget(QGLFormat(QGL::SampleBuffers), parent), helper(helper)
{
elapsed = 1;
reverse = false;
}

void GLWidget::animate()
{
//elapsed = (elapsed + qobject_cast<QTimer*>(sender())->interval()) % 1000;
if(reverse)
elapsed = elapsed + 0.01;
else
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)
{
QPainter painter;
painter.begin(this);
painter.setOpacity(elapsed);
painter.setRenderHint(QPainter::Antialiasing);
helper->paint(&painter, event, elapsed);

painter.end();

}@

And here the repaint's call

@GLWidget *openGL = new GLWidget(&helper, this);

this->setCentralWidget(openGL);

QTimer *timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), openGL, SLOT(animate()));
timer->start(10);@

Thanks a looooooot!

[SGaist]

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.

[Speechless]

Hi,

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!

[SGaist]

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

[Speechless]

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 :-)

Thanks again!

[SGaist]

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 :)