[Qgis-developer] Approximate reprojection for vectors

[Andrew Chapman]

On Sun, 2011-10-02 at 15:02 +0200, cavallini at faunalia.it wrote:
> I do not see reprojection of vectors significantly slowing down
> rendering. Anyone does?
... and my 5c.
I haven't looked at the code so the following may be inappropriate, but in
the late 80's my team (Sigmex Ltd) had the world's fastest vector graphics
engine (HW + SW). We were constantly pushing the envelope and validating
against industry accepted benchmarks and real-world tests. 
One area that delivered a surprising 40% overall improvement was the
detection and handling of "single pixel" vectors - if you know the bounding
rectangle will be resolve to a pixel at the zoom level, it simplifies to a
point. This then simplifies 'n' points and lines to a single transformation.
The fastest transformation is the one you didn't need to do and so
skipped... as long as the test is simple and minimal overhead.

Andrew Chapman