[Qgis-developer] What about OpenGL renderding ?

[Marco Hugentobler]

Hi all

Qt already has an open gl based paint device ( QGLPixelBuffer ), so the 
effect of hardware acceleration can be tested just by replacing the 
QImage with a pixel buffer. I did this years ago and ( can't remember 
the Qt version ), the rendering with QGLPixelBuffer was slower on my 
computer compared to QImage. Additionally, the graphical quality was lower.

The reason might be that transfer of data to the GPU is slow, but 
rendering is fast. So it would probably need a non-QPainter based 
approach to store the data at the GPU and use repeatedly then. Afaik 
Hugo Mercier has experience using a non-QPainter based approach (as used 
in the 3D example city of Lyon). However, such an approach would require 
very fundamental changes in lots of places in the core library.


Regards,
Marco


On 24.10.2013 12:03, A Huarte wrote:
> There is also a more ambitious option, detach in QGIS the render of 
> the objects of the painting technology ( Currently Qt+QPainter ) using 
> interfaces as Ogre, Irrlicht or OSG does.
>
> Then could be implemented several 2D/3D-CPU/GPU renderers ( Qt4-5, 
> OpenGL, OpenGL ES, Ogre, OSG ...) being the rendering mode (2D/3D or 
> CPU/GPU) changeable from a single application option.
>
>
>
>     ------------------------------------------------------------------------
>     *De:* kimaidou <kimaidou at gmail.com>
>     *Para:* vincent.ml at oslandia.com
>     *CC:* qgis-developer <qgis-developer at lists.osgeo.org>
>     *Enviado:* Jueves 24 de octubre de 2013 11:59
>     *Asunto:* Re: [Qgis-developer] What about OpenGL renderding ?
>
>
>
>
>     2013/10/24 Vincent Picavet <vincent.ml at oslandia.com
>     <mailto:vincent.ml at oslandia.com>>
>
>         Hello,
>
>         Le jeudi 24 octobre 2013 09:54:06, kimaidou a écrit :
>         [..]
>
>         > In web mapping contexts, major improvements are made in 2D
>         vector rendering
>         > speed by using WebGl technology, such as in upcoming
>         OpenLayers 3. As a
>         > user point of view, improvement seems huge compared to
>         classical DOM or
>         > more advanced CANVAS renderer.
>         >
>         > What about using graphic card to help improve rendering
>         performance in QGIS
>         > ? Would this help a lot, or at the contrary would this be a
>         dead-end ?
>
>         We would probably begin with porting QGIS to QT5, as OpenGL
>         support has been
>         added to QT5 and improved in 5.1.
>         See for example :
>         http://qt-project.org/doc/qt-5.0/qtopengl/2dpainting.html
>
>         Otherwise, reimplementing an pure OpenGL rendering engine
>         seems a big effort.
>         And we still would want to have a classic renderer for
>         non-accelerated
>         hardware.
>
>
>     Thanks for this ressource page about qt5
>     I agree with you : why reinvent the wheel if QT5 proposes needed
>     and mature tools. I just hope porting QGIS to Qt5 won't be so hard
>     that it would postpone it to 3.0 though :) Have any discussions
>     begun on this topic among QGIS devs ?
>
>
>
>         One really interesting thing is that it would open the door
>         for viewing 3D
>         objects in QGIS. As for now to be able to see PostGIS 3D
>         objects we had to
>         develop our own external 3D viewer (horao). For that to happen
>         we would need
>         real 3D geometry support in QGIS too.
>
>
>
>     Exactly, I have seen your video for Lyon town project, this is
>     great ! I can only imagine what a speed improvement it would bring
>     for "simple" 2D painting !
>
>
>
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-- 
Dr. Marco Hugentobler
Sourcepole -  Linux & Open Source Solutions
Weberstrasse 5, CH-8004 Zürich, Switzerland
marco.hugentobler at sourcepole.ch http://www.sourcepole.ch
Technical Advisor QGIS Project Steering Committee

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