[Qt-interest] Performance issues with Graphics View Framework

[Enrico Ros]

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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