[Qt-interest] Performance issues with Graphics View Framework

[Simone Artesino]

Enrico wrote :  (you're copying memory
to and from the video board many times with the current approach),

Ok Enrico, but let's consider now these tests result, made on atom chipset
polusbo.
running a 30 fps timer,
when use as viewport a Widget I obtain 30 fps and 19% cpu load.
when use as viewport a QGLWidget I obtain 5 fps and 67% cpu load.
these results are not influenced from switching viewport update policy.

What I can infer from this result?
my qpixmap copy is well hardware accelerated when I use a Widget (and is
stored in gpu internal memory I guess), instead when I use a QGLWidget the
copy is translated in a very bad open-gl code that makes several copies of
memory from ram-cpu memory to gpu.

Is a correct deduction? what you think about it?




2009/7/20 Enrico Ros <enrico.qt at email.it>

> On Monday 20 July 2009 16:22:08 Simone Artesino wrote:
> > *) I'm sure that I'm running openGL on gpu (no software-only mode)
> > -) I'm using the latest qt 4.5.2
> > --) I've take care off disable antialias and other cpu consuming.
> >     setRenderHint(QPainter::Antialiasing,false);
> >     setRenderHint(QPainter::TextAntialiasing,false);
> >     setRenderHint(QPainter::HighQualityAntialiasing,false);
> >     setRenderHint(QPainter::NonCosmeticDefaultPen,false);
> >     setRenderHint(QPainter::SmoothPixmapTransform,false);
> > ---)I've tried both MinimalViewportUpdate, SmartViewportUpdate,
> > BoundingRectViewportUpdate, FullViewportUpdate but the the performances
> > difference between the two viewpot still remains
> > ----)About poulsbo I'm pretty sure to use the latest and stable gma
> drivers
> >
> > x) In my animation i do the following work: like a slotmakine i
> vertically
> > move a set of 3 simbols of a 10 symbols stripe.
> >
> > I obtain that result in the following manner.
> >
> > Load a QImage that represent a stripes of 10 different symbols
> > striscia = new QImage("media/images/striscia.png");
> > Randomly choose a sequence of this ten symbols.
> > Using this sequence i create an empty QPixmap and draw on it the
> > corresponding symbols taken from the QImage.
> >
> > Animation cycle :
> > Using a clipping rectangle and the QPixmap::copy i copy the right portion
> > of the stripe in the screen that simulate a scrool of the stripe.
>
> I think the clipping rectangle may hurt performance. You could convert this
> type of animation by pushing the texture to OpenGL ONCE (you're copying
> memory
> to and from the video board many times with the current approach), and use
> GL
> commands inside the animation loop.
>
> The animation should "scroll the texture coordinates" of the 4 vertex of
> the
> rectangle and draw always the same rectangle. Saving will be huge ;-)
>
> Ciao,
> Enrico
>
>
>
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