[OSM-talk] SOTM relations workshop: results

[Ben Laenen]

On Wednesday 20 August 2008, Frederik Ramm wrote:
> Multipolygons
> -------------
>
> [...]
>
> The "no segmentation" rule is important because there are renderers
> already which use different colours for an area boundary than for the
> area itself, and such segments will then show up on the maps.
>
> Unsolved problem: How can we create really large areas without having
> to have a 10,000 node "outer" way. Should be possible with relations
> - e.g. multipolygon with >1 "outer" members that connect - but
> unsure.

In some own rendering I do I solved this for now quite easily for water 
polygons, which are usually segmented into smaller areas: the trick is 
to mask the border with the inner area colour. To get a border, you 
first (before inner area colour border) render a slightly thicker 
border. Downside: it will show the areas a tiny bit bigger than they 
are, but it's basically just one pixel, not disturbing the picture at 
all. Take 
http://fenix.cmi.ua.ac.be/~p015259/osm/map-antw-noord-west-024.png 
(warning: 5MB) as an example to see it in effect. The whole river and 
all docks in the port are made out of many segments, but you can't see 
them (actually you can, if you investigate the exact RGB values). It's 
a bit of a trade-off between how much thicker you want to have the 
areas vs the original semgent borders being visible.

Of course, better and more complex solutions may exist, but for now this 
is quite easy to implement and it'll do for me :-)

Greetings
Ben