[Qt-interest] Modification for faster coordinate clipping in QOutlineMapper

[Marco Hugentobler]

Hi André (and list)

Thank you for the hint. I tried to followed the tutorial at 
http://qt.gitorious.org/qt/pages/GitIntroductionWithQt

Now I have a problem with the last step (Sending your feature for review). 
Note that I'm new to git (I have been an svn user so far), so I hope you could 
help me.

So I created a login on gitorious (mhugent), my branch is called 
'faster_outline_clip'. Then I tried to do git push like this:

marco at marco-laptop:~/src/qt$ git push 
git at gitorious.org:~mhugent/mhugents_clone.git faster_outline_clip
Permission denied (publickey).
fatal: The remote end hung up unexpectedly


Could you give an exact step-by-step instruction on what I need to do?

Thanks,
Marco



Am Samstag, 5. September 2009 10.29:43 schrieb André Somers:
> I understand that patches are more likely to get accepted if you create a
> branch for it in the Qt GIT repository, and tell the developers about it.
> Just a tip. I think it would be a useful improvement to Qt, so go for it! I
> ran into similar issues by the way in the time I was developing Cumulus
> (http://cumulus.kflog.org).
>
> André
>
> -----Oorspronkelijk bericht-----
> Van: qt-interest-bounces at trolltech.com
> [mailto:qt-interest-bounces at trolltech.com] Namens Marco Hugentobler
> Verzonden: zaterdag 5 september 2009 8:05
> Aan: qt-interest at trolltech.com
> Onderwerp: [Qt-interest] Modification for faster coordinate clipping in
> QOutlineMapper
>
> Hi
>
> For applications that display geographic data (lakes), it is quite common
> to
>
> display large polygons (100000 vertices).
>
> One problem we have is that when zooming in very close, drawing polygons
> can
>
> take very long time (several minutes). Doing a bit of debugging, I found
> that
> most of the time is spent in the clipping code at
> src/gui/painting/qoutlinemapper.cpp, function QOutlineMapper::clipElements
> where the coordinates are clipped to +- 32767
>
> In our GIS application, we already have code to do coordinate clipping
> based
>
> on Sutherland and Hodgman's polygon-clipping algorithm and I noticed that
> it
>
> runs much faster (but seems to me it is only suitable for straight line
> segments). So I extended QOutlinemapper to use this algorithm for large
> pathes
> without curves and it seems to work quite well for me.
>
> If there is an interest in my modifications, the changed source files are
> available at:
>
> www.hugis.net/qt/qoutlinemapper_p.h
> www.hugis.net/qt/qoutlinemapper.cpp
>
> I hope that this performance improvement (or any other improvement that
> enhances clipping speed) can be included in future versions of Qt.
>
>
> Regards,
> Marco


-- 
Dr. Marco Hugentobler
HUGIS - GIS Programmierung und Beratung Hugentobler
Honrainweg 5
CH-8038 Zürich
marco at hugis.net