[Qgis-developer] questions on rendering

[Mohammed Rashad]

On Tue, Sep 27, 2011 at 8:10 PM, Martin Dobias <wonder.sk at gmail.com> wrote:

> On Tue, Sep 27, 2011 at 4:18 PM, Mohammed Rashad
> <mohammedrashadkm at gmail.com> wrote:
> > Hi All,
> > I am developing tiled vector rendering in OSSIM. I like the Qgis vector
> > rendering system
> > point.shp contains 9,99,999 points which are generated by grass for using
> > v.random and ~27MB in size
> > roads.shp contains 2,28,068 linestrings and is ~50MB in size
> > these point.shp and roads.shp data gets rendered in ~10 sec
> > When I read vector using ogr and parse feature and draw point/linestring
> my
> > application taking about 40 sec to render point.shp
> > and
> > I am using Qt4 with QPainter not QGraphicsView
> > How came this time gap?
>
> Most likely you have some inefficiencies in your implementation.
>
Can you tell where i have inefficiencies I do direct rendering Qt Painter
and OGR?

>
> > i see Rtree and pal libs in src/core source code
> > Does they have any role in rendering?
>
> No - unless you also draw labels.
>
> > Does QGIS Rendering uses threading?
>
> No - only in threading branch which has not yet been integrated.
>
> > How to get a minimal of QGIS code to hack it and build a new vector
> > rendering because I need it to make it tiled rendering vectors?
>
> You can use qgis_core library to do tiled drawing.
>
> > How to improve performance in rendering without qgis?
>
> Learn how to profile programs - i.e. get time spent in individual
> functions, analyze the results and fix the places where most of the
> time is spent.
>

How to do profiling? how is works? please tell me some samples for
profiling..

>
> Martin
>



-- 
Regards,
   Mohammed Rashad K M
   M.S. (By Research) student
   Lab for Spatial Informatics
   Department of CSE
   International Institute of Information Technology
   Hyderabad, India
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