Getting back to Stefan's 1000 point linestring problem, the issue here is
clipping extents. As he determined, it is much faster when a large
linstring is broken into 2 point linestrings. This is probably because
instead of an expensive clipping operation to find the intersection of the
1000 point linestring with the viewport, most of the 2 point linestrings are
being trivially rejected as being outside. This suggests that we could
implement your solution behind-the-scenes to optimize drawing, however I
believe that the multiple 2 point linestrings would appear visually
different at the shared endpoints due to being drawn twice, so this is
probably not a good idea. Any other kind of optimization would probably be
best performed in JTS. Perhaps we could interest Martin in the test case.
:-)
regards,
Larry
On Fri, Feb 19, 2010 at 11:40 AM, Stefan Steiniger <sst...@geo.uzh.ch>wrote:
> mhm.. ok, so I would guess the problem is related to the size of the
> geometries and its drawing?
> I recently had a problem - drawing a linestring that consisted of more
> than 1000 points. I couldn't do anything for 20-30 seconds on MS Vista,
> my XP was a bit faster. However, the problem solved when I connected the
> 1000 points with linestrings that have only a start and endpoint, i.e.
> instead of drawing 1 linestring a had to draw now 500, but here the 500
> lines could be drawn one after each other, and everything is done within
> 2-3 seconds (instead of 20 secs)
>
> (if Larry wants to test, I can send that linestring?)
>
> however, I am not sure why working with the 1000 points linestring is so
> slow (i.e. does paint make some tests?)
>
> stefan
>
> luca marletta wrote:
> > luca marletta
> > www.beopen.it
> >
> >
> >
> > On Fri, Feb 19, 2010 at 5:42 PM, Larry Becker <becker.la...@gmail.com>
> wrote:
> >> Hi luca,
> >>
> >> When you try to select features, does the status bar quickly show your
> >> selection count, even though no selection handles appear?
> >>
> >> If not, this explains why the right click menu is not appearing. It
> needs
> >> selection information to enable or disable options.
> >
> > Larry, no I had not much problem with showing selection count, is anyway
> quick.
> >
> > I noticed an important stuff.
> >
> > May dataset is full of large and aggregated geometry and in this case
> > I guess geometry index can not much help.
> >
> > If I explode all, I reduce the delay a lot.
> >
> > luca
> >
> >
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--
Larry Becker
Integrated Systems Analysts, Inc.
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