[Qgis-developer] Re: Welcome to 4 QGIS students in Google Summer of Code 2012

Evgeniy Pashentsev ugnpaul at gmail.com
Sun May 13 11:21:30 PDT 2012


I am that Eugenpaul doing vector layer generalization. Happy
to be accepted, but it is also quite a responsibility, so I am
feeling a very special mix of emotions right now. You may
remember my proposal, but the work plan has been changed
a bit, so I will briefly tell you what I have decided to do after
several conversations with my mentor, Alexander Bruy.
1. My first aim now is to implement generalization for a
collection of objects keeping their topological relations.
Current implementation handles only one feature and avoids
new intersections as a result of generalization. I'll take its
base algorithm, the Douglas-Peucker, and add tracking of
connected edges of the neighboring objects.
2. Then I will implement the on-the-fly generalization to
speed up rendering. According to some tests done by
Alexander [0], a simple distance threshold routine followed by
the Douglas-Peucker algorithm shows significant reduction
of the rendering time, especially with complex style lines.
3. Then I will look into the render cache realization. It is the
right way of speeding up rendering, maybe there is a way to
improve it.
4. At last, if I will have enough time, I'll try to adapt existing
feature cache patch to the last QGIS version.
Everything is planned to be supported by unit tests.
All the progress will be described in the blog [1].
If you have any ideas on how to do these things better,
please let me know.

 - shows dependence of rendering time on the number of lines
and their style, "+gen" shows rendering time with on-the-fly
[1] http://blogs.gis-lab.info/ugnpaul/

Thank you!
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