Fast(est) way of drawing simple objects

[eperfa]

Yes, I know that, however as a first version I wanted to implement something that is platform-independent.

Regarding the timing issues, I have changed from QTimeLine to a simple QTImer implementation (I can't even tell you why it wasn't my first choice), and it also made a difference.

timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(updateRect()));
timer->start(35);
 
QTimer *timer2 = new QTimer(this);
timer2->singleShot(2000, this, SLOT(endTest()));

timer = new QTimer(this);
connect(timer, SIGNAL(timeout()), this, SLOT(updateRect()));
timer->start(35);

QTimer *timer2 = new QTimer(this);
timer2->singleShot(2000, this, SLOT(endTest()));

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Still, if you have some ideas about optimizing the redrawing itself, I'm open to any suggestions. (I'll try the simple widget method soon)

[JohannesMunk]

Hi!

Concerning QTimer accuracy: Also we get slightly off topic we get back to it at the end:
http://www.qtcentre.org/threads/4031...Timer-accuracy

So I recommend timer->start(16); That will give you approximately 60 fps. Just change your modulo for slower flips accordingly.

If you want really accurate timing, you will need to sync your updates with the screen refresh. Thats called vertical-sync (vsync) and can easily be enabled on a QGLWidget.

QGLFormat glFormat(QGL::SampleBuffers);
glFormat.setSwapInterval(1);
QGLWidget* glwidget = new QGLWidget(glFormat);

QGLFormat glFormat(QGL::SampleBuffers);
glFormat.setSwapInterval(1);
QGLWidget* glwidget = new QGLWidget(glFormat);

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Implement a frames per second counter - while that one is fixed at your screen refresh rate you don't need to worry about faster drawing routines.

You will probably want to subclass a QGLWidget. Manual swapbuffer is shown in the helloGL ES examples shipped with qt. Couldn't find a doc link for them. when vsync is active the call to swapBuffers will not return until the refresh occured. Thats how the timing is going to be very precise. If you update your GLWidget with a timer as the helloGL example does, you should call qApp()->processEvents() somewhere to keep your GUI responsive. The FPS counter implementation of that example is mod 100. You will have to adapt that logic, maybe by starting a custom timer with an intervall of 1000ms and resetting the frames-counter in it.

HIH

Joh

[wysota]

Still, if you have some ideas about optimizing the redrawing itself, I'm open to any suggestions. (I'll try the simple widget method soon)

I would second what tbscope says - get rid of GraphicsView and use a plain widget.

[JohannesMunk]

That was quite a cross posting.. Guess I spent too long editing that post.

Joh

[eperfa]

Thank you guys, especially Joh! That was exactly the knowledge I was missing - I'll definitely give it a try in the next couple of days.