[Tagging] Tunnels and bridges

Peter Wendorff wendorff at uni-paderborn.de
Fri Feb 1 13:37:49 GMT 2013

Am 01.02.2013 14:19, schrieb Martin Koppenhoefer:
> 2013/2/1 Peter Wendorff <wendorff at uni-paderborn.de>:
>> case 2: the "legacy style" of at least one bridge highway is painted that
>> wide that it's outer line(s) is/are outside of the bridge area (including
>> casing).
>> This way the "legacy style"s bridge casing is visible where the bridge area
>> or it's casing is drawn on top of it, and the bridge area is covered by the
>> highway on top.
>> To summarize:
>> If the bridge outline is hidden underneath the rendered road, the old bridge
>> casing is not hidden (as it's per definition outside of the rendered road).
>> Therefore it's not a problem.
> Yes, it is not a real show stopper, but the rendering result in this
> way would be somehow coincidental (there could for instance be
> interferences from the casing and the polygon leading to quite ugly
> artifacts). The cleaner solution would be to suppress rendering of
> casings when there is an outline polygon.
Sure, but this would occur only in case a renderer
- renders the bridge-area
- renders the old bridge casing
- and does not calculate the "conflict" in it's preprocessing.

of course we could add a rendering hint like
part_of_a_bridge_area=yes to make it easier for renderers to determine 
that case,
but on the other hand it's a reasonable preprocessing step to calculate 
these conflicts (sharing nodes between ways having bridge=* and ways 
having the bridge-area-tag => remove the bridge=yes tag for rendering).


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