[Development] Scenegraph Triple Buffering

[Dietrich.Gossen at conti-engineering.com]

The used hardware is: i.MX6 Sabrelite (with powerful gpu from vivante)
Used Qt-Version: 5.0.0 Alpha with eglfs plugin

The Qt Application contains scaling, rotations and moving of images. The 
application is a comination of QML and C++.
I am searching for the bottleneck. 

The hellogl_es2 example is running with 75 fps (with vsync on). But 
hellogl_es2 is not using QML.

My first idea was to enable triple buffering, and compare the result to 
double buffering with vsync.

Best regards

Dietrich 



Von:    <gunnar.sletta at nokia.com>
An:     <Dietrich.Gossen at conti-engineering.com>
Kopie:  <development at qt-project.org>
Datum:  28.06.2012 11:39
Betreff:        Re: [Development] Scenegraph Triple Buffering




On Jun 28, 2012, at 10:58 AM, ext Dietrich.Gossen at conti-engineering.com 
wrote:

> Hi, 
> 
> There is some Qt 5.0 documentation available about 
QSurfaceFormat::SwapBehavior. There is a constant called 
QSurfaceFormat::TripleBuffer . 
> Is this feature already implemented and tested in Qt 5 Alpha? 

This parameter is picked up by the platform's OpenGL implementation if 
anything, but none of our desktop backends currently make use of this as 
the buffering policy is typically decided for us by the system. This is 
mostly a hint to be picked up by EGL implementations where applicable.

> The reason I am asking, is because we are facing the typical issues with 
Double buffering and vsync turned on. 
> The fps drops to 30. 

What system / setup is this and what are you trying to draw? There is no 
reason why double buffering combined with vsync should result in 30FPS, 
unless each frame takes in the range 17-33ms to draw. Does this happen 
also for a very simple scene?

cheers,
Gunnar


> Thanks 
> 
> Best regards 
> 
> Dietrich Gossen
> _______________________________________________
> Development mailing list
> Development at qt-project.org
> http://lists.qt-project.org/mailman/listinfo/development


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