[OSM-talk] Area Support /Osmarender

[Etienne]

On 9/16/06, Chris Morley <c.morley at gaseq.co.uk> wrote:
>
> Thomas Walraet wrote:
> > Chris Morley a écrit :
> >> When drawing areas with the way method you have to watch that all the
> >> segment directions are correctly aligned. This is annoying (direction
> >> has nothing to do with area)
> >
> > Direction could have a lot to do with area.
> >
> > For example, we can agree on always put the water on the right of a
> > coast line :
>
> > If water is always on the right side of the "way" that represent the
> > water/land demarcation, a renderer could draw the coast-line properly
> > even if only BCD points are on the rendered dataset.
> >
> You are right, it was an ill-advised statement. Indeed I had open a
> diagram http://www.w3.org/TR/SVG11/painting.html#FillProperties showing
> how SVG rendering of areas can depend on the the path direction. But
> what matters is the *path* direction and not the individual *segment*
> directions. An ordered node-list inherently has a path direction to use
> if necessary and I still think it is a cleaner area representation.


The problem is with segment direction being an implied attribute of a
segment.

If you have two ways that want to share the same segment but in opposite
directions you encounter the same problem.

The solution is to eliminate segments from the database altogether.  Ways
become ordered lists of nodes.   Segments become ways with just two nodes.
And you need to allow a hierarchy of ways to allow multiple sub-paths to be
grouped together.

Etienne



Chris
>
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