[Qt5-feedback] 400000 chips example in QML?

[Samuel Rødal]

On 05/12/2011 12:11 PM, ext Kishore wrote:
> On Thursday 12 May 2011 2:38:42 PM Samuel Rødal wrote:
>> On 05/12/2011 10:55 AM, ext Kishore Jonnalagadda wrote:
>>> As was asked in the blog
>>> http://labs.qt.nokia.com/2011/05/11/responses-to-qt-5/.
>>>
>>> I would like to know if QML can scale well enough. It seemed that
>>> QGraphicsView used QGraphicsItems as they were much lighter than using
>>> QWidget. But with QML each item will again be a QObject. Does this not
>>> add too much overhead? Take the example of the 400000 chips for
>>> reference.
>>>
>>> --
>>> Cheers,
>>> Kishore
>>
>> QML isn't really meant for such use-cases (visualization of large data
>> sets). The right way of doing this would be to use scene graph or OpenGL
>> directly (and you'd get much better performance than in the 40000 chips
>> demo).
>
> So this demo in Qt5 would use C++ code for the UI and not QML? So then there
> really are a lot of use cases where QML is not entirely suitable. Right?
>
> Now, would the coding in c++ with scene graph (Sorry, i don't know much about
> the technology) would be the Qt5 way? Does it replace QGV?
>
> Of course, OpenGL is an alternative just as it is today. But would Qt provide
> a way of doing it like it now does with QGV or is direct OpenGL the
> "recommended" way?

QML main focus is application UIs, but that doesn't mean it's a good fit 
for all UIs. For example, the 3D model editor in Maya is also a user 
interface, one which requires a fully specialized solution. I would say 
the same for other UIs where you need to do visual manipulation of huge 
data-sets.

For UIs that fall outside of the scope of QML, QGraphicsView is still an 
option, as is using raw OpenGL with the enablers that Qt provides 
(QGLFramebufferObject, QGLShaderProgram, etc), or the higher level 
Qt/3D, as well as other scene graph APIs like OGRE and OpenSceneGraph. 
The new Qt scene graph is also an option, but it's designed more with 
the use cases of QtQuick 2.0 in mind and doesn't have a convenience 
layer like QGraphicsView.

I don't think anyone is saying that QML is the way _all_ graphics should 
be done in the future.

--
Samuel