[GRASS-dev] display/drivers/HTMLMAP status
hamish_nospam at yahoo.com
Wed Feb 14 06:52:50 CET 2007
Glynn Clements wrote:
> It's relying upon the fact that a specific sequence of horizontal
> lines is indistinguishable from a filled polygon with the existing
> X/PNG drivers.
> > Will the current d.vect method be faster than using lib fns which
> > will take time rendering polygons which will end up being off
> > screen?
> It depends upon the specific case.
I'll throw in my typical vector case: a high resolution vector coastline
of the entire country + the 1000s of nearshore islands, all stored in
a single vector map.
> In terms of protocol overhead, sending polygon vertices involves
> sending less data than sending lots of horizontal lines, unless:
> 1. The polygon edges are small (typically < 1 pixel high), or
this is true when zoomed out to view entire country.
> 2. Most of the polygons are off-screen, and d.vect doesn't explicitly
> check for this at the polygon level.
> 3. A substantial proportion of the data is made up of polygons which
> are mostly off-screen, and it doesn't do polygon clipping.
this is true when zoomed into a specific part of the coastline.
90% of the time I am working at either one of those two scales.
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