Problems displaying a very large polygon

[Mark Leslie]

It will always run slow since it always needs to look at the entire 
shape.  It will run even slower for areas with a great deal of detail, 
such as the coastline in your example.  Tiling it will reduce the time 
to find the appropriate section to render, but to speed the rendering, 
you need to simplify your data for the desired scale so that you aren't 
rendering dozens of points into a single pixel.  Brock mentioned the 
PostGIS simplify function, which is what I typically use.
Mark

Frederico Lucca wrote:
> Mark,
> 
> Thanks for the explanation, but in this case why some sections of the
> polygon are processed faster than others?
> 
> Best regards,
> 
> Fred
> 
> On 5/4/06, Mark Leslie <mark at refractions.net> wrote:
> 
>>
>> Fred,
>> The problem with large polygons like this is that loading a small
>> section like you're doing still requires the entire polygon to be
>> processed.
>> One solution is to break the polygon into tiles closer to the size you
>> intend to display. This way the indexes can be used more effectively,
>> and only the areas you're displaying needs to be processed.
>> Mark
>>
>> Frederico Lucca wrote:
>> > Hello list,
>> >
>> > I have a layer with a single polygon, but it has 131570 points. It's 
>> the
>> > territory from brazil.
>> > When I try to export a gif showing only a small piece, like 1/30 from
>> the
>> > total, this spends 30 seconds (attached).
>> > I observe that when the coast is more irregular this is slower to
>> export.
>> > Other layers are very quick to export, something like 1 or 2 second.
>> > How I can deal with this problem?
>> >
>> > Thanks in advance.
>> >
>> > Fred
>> >
>> > --
>> > "Everything under the sun is in tune
>> > But the sun is eclipsed by the moon"
>> >
>> >
>> > 
>> ------------------------------------------------------------------------
>> >
>>
>>
> 
> 
> -- 
> "Everything under the sun is in tune
> But the sun is eclipsed by the moon"
>